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Today, there is a surplus of American alligator hides in the market (Fannin, Penn, & Stannard, 2021). Finding new uses for alligator leather is critical. However, alligator is challenging to use in apparel products. The irregular shape of the hide can make it difficult to cut items and garments require numerous skins (Belleau, Marquette, & Summers, 2004). Previously, Belleau et al. (2004) reported best practices for utilising alligator leather in apparel. This investigation was almost 20 years ago and did not use experimental patternmaking methods. The purpose of the present research was to apply experimental patternmaking methods to determine the best approach for utilising more of each alligator hide and maximising the creative potential of alligator leather. To investigate, a design team completed five designs. Each design employed a different experimental patternmaking method with alligator leather. Key requirements for designing with alligator were considered and combined by the design team. [ABSTRACT FROM AUTHOR]

Sedation and general anaesthesia of crocodilians pose unique challenges due to their aggressive nature, poikilothermic physiology, and specific anatomical and physiological characteristics, all factors that complicate crocodilian anaesthesia. This review aimed to systematically review the literature regarding sedation and general anaesthesia of crocodilians with focus on efficacy and impact on vital parameters. A systematic literature search was performed according to PRISMA guidelines on May 2, 2023 in the databases Embase, PubMed, Scopus and Web of Science. Publications were excluded based on predefined exclusion criteria, which encompassed non-standard publications and publications unrelated to crocodilians, with fewer than five animals and/or with insufficient data on sedation and general anaesthesia. Five key factors were used to evaluate the strength of evidence: number of included animals, study design, definition of recovery time, blinded assessment of recovery and conflict of interest. Ten publications were included in this systematic review. Drugs used included alpha-2-adrenoceptor agonists, dissociative anaesthetics, benzodiazepines, neuromuscular blocking agents, propofol, alfaxalone, and inhalant gasses. The studies included in total 55 Alligator mississippiensis, 110 Crocodylus porosus, 15 Crocodylus johnstoni, and 15 Crocodylus niloticus. Factors such as temperature, administration route, dose, species, and age influenced protocols for sedation and general anaesthesia of crocodilians. The studies included used five different study designs. Only one study included a control group, done on retrospectively collected data. Blinded recovery assessments and declarations of no conflict of interest were noted in some studies. The use of four distinct recovery definitions posed challenges to comparability in this systematic review. The studies reported that medetomidine provided stable and reversible sedation, although it depressed heart rate. Alfaxalone was less stable outside the optimal temperature range. Intubation and inhalation anaesthesia were effective, and adrenaline reduced the length of the recovery period. Overall, the review provides valuable insights for veterinarians, researchers, and wildlife professionals involved in sedation and general anaesthesia of the crocodilian species, however, the literature is limited, and further research is needed to improve evidence-based medical management. [ABSTRACT FROM AUTHOR]

"Double scale" is a poorly characterized skin defect of crocodilians that drastically reduces the economic value of crocodilian skin. This study investigated the morphology and pathogenesis of double scale in a ranching farm of American alligators (Alligator mississippiensis). We compared the histopathology of skin and selected organs (liver, lung, kidney, heart, spleen, intestine, and brain) of alligators with double scale against healthy control animals, together with serum and liver vitamin and mineral levels. Skin affected with double scale had statistically significant hyperkeratosis, epidermal atrophy, and increased basal cell degeneration compared with control alligators (P <.0001). Interestingly, all alligators with double scale had varying degrees of hepatic fibrosis. Feed analysis showed that alligators that had double scale and hepatic fibrosis had prolonged dietary exposure to high levels of vitamin A, iron, and copper. Serum analysis indicated that levels of zinc (p <.0001), copper (P <.05), and vitamin E (P <.002) were significantly lower in alligators with hepatic fibrosis and double scale compared with controls. Finally, immunohistochemical analysis of skin with double scale showed a marked reduction in immunolabeling with the zinc-binding protein metallothionein. These results suggest that zinc deficiency, in combination with other micronutrient anomalies, may play a role in the pathogenesis of double scale in alligators with liver fibrosis. [ABSTRACT FROM AUTHOR]

Background: West Nile virus (WNV), Everglades virus (EVEV), and five species of Orthobunyavirus were isolated from mosquitoes collected in the Everglades in 2016–2017. Prior studies of blood meals of mosquitoes in southern Florida have related findings to acquisition and transmission of EVEV, St. Louis encephalitis virus, and WNV, but not the Orthobunyavirus viruses associated with the subgenus Melanoconion of the genus Culex. Materials and Methods: In the present study, blood-fed mosquitoes were collected in the Everglades in 2016, 2017, 2021, and 2022, and from an industrial site in Naples, FL in 2017. Blood meals were identified to host species by PCR assays using mitochondrial cytochrome b gene. Results: Blood meals were identified from Anopheles crucians complex and 11 mosquito species captured in the Florida Everglades and from 3 species collected from an industrial site. The largest numbers of blood-fed specimens were from Culex nigripalpus, Culex erraticus, Culex cedecei, and Aedes taeniorhynchus. Cx. erraticus fed on mammals, birds, and reptiles, particularly American alligator. This mosquito species could transmit WNV to American alligator in the wild. Cx. nigripalpus acquired blood meals primarily from birds and mammals and frequently fed on medium-sized mammals and white-tailed deer. Water and wading birds were the primary avian hosts for Cx. nigripalpus and Cx. erraticus in the Everglades. Wading birds are susceptible to WNV and could serve as reservoir hosts. Cx. cedecei fed on five species of rodents, particularly black and hispid cotton rats. EVEV and three different species of Orthobunyavirus have been isolated from the hispid cotton rat and Cx. cedecei in the Everglades. Cx. cedecei is likely acquiring and transmitting these viruses among hispid cotton rats and other rodents. The marsh rabbit was a frequent host for An. crucians complex. An. crucians complex, and other species could acquire Tensaw virus from rabbits. Conclusions: Our study contributes to a better understanding of the host and viral associations of mosquito species in southwestern Florida. [ABSTRACT FROM AUTHOR]

Among extant species, the ability to sample the extremes of body size—one of the most useful predictors of an individual's ecology—is highly unlikely. This improbability is further exaggerated when sampling the already incomplete fossil record. We quantify the likelihood of sampling the uppermost limits of body size in the fossil record using Tyrannosaurus rex Osborn, 1905 as a model, selected for its comparatively well‐understood life history parameters. We computationally generate a population of 140 million T. rex (based on prior estimates), modelling variation about the growth curve both with and without sexual dimorphism (the former modelled after Alligator mississippiensis), and building in sampling limitations related to species survivorship and taphonomic bias, derived from fossil data. The 99th percentile of body mass in T. rex has likely already been sampled, but it will probably be millennia before much larger giants (99.99th percentile) are sampled at present collecting rates. Biomechanical and ecological limitations notwithstanding, we estimate that the absolute largest T. rex may have been 70% more massive than the currently largest known specimen (~15,000 vs. ~8800 kg). Body size comparisons of fossil species should be based on ontogenetically controlled statistical parameters, rather than simply comparing the largest known individuals whose recovery is highly subject to sampling intensity. [ABSTRACT FROM AUTHOR]

The evolution of archosaurs provides an important context for understanding the mechanisms behind major functional transformations in vertebrates, such as shifts from sprawling to erect limb posture and the acquisition of powered flight. While comparative anatomy and ichnology of extinct archosaurs have offered insights into musculoskeletal and gait changes associated with locomotor transitions, reconstructing the evolution of motor control requires data from extant species. However, the scarcity of electromyography (EMG) data from the forelimb, especially of crocodylians, has hindered understanding of neuromuscular evolution in archosaurs. Here, we present EMG data for nine forelimb muscles from American alligators during terrestrial locomotion. Our aim was to investigate the modulation of motor control across different limb postures and examine variations in motor control across phylogeny and locomotor modes. Among the nine muscles examined, m. pectoralis, the largest forelimb muscle and primary shoulder adductor, exhibited significantly smaller mean EMG amplitudes for steps in which the shoulder was more adducted (i.e., upright). This suggests that using a more adducted limb posture helps to reduce forelimb muscle force and work during stance. As larger alligators use a more adducted shoulder and hip posture, the sprawling to erect postural transition that occurred in the Triassic could be either the cause or consequence of the evolution of larger body size in archosaurs. Comparisons of EMG burst phases among tetrapods revealed that a bird and turtle, which have experienced major musculoskeletal transformations, displayed distinctive burst phases in comparison to those from an alligator and lizard. These results support the notion that major shifts in body plan and locomotor modes among sauropsid lineages were associated with significant changes in muscle activation patterns. [ABSTRACT FROM AUTHOR]

Human–wildlife interactions are increasing globally due to human population growth and development. Wildlife often develop an increased tolerance of humans through the learning processes of habituation, but habituation of large predators can increase risks to humans. Aversive conditioning is a management strategy that operationalizes learning to reduce wildlife tolerance of humans and thereby improve human safety. However, developed landscapes may select for wildlife phenotypes that are resistant to learning via aversive conditioning. We investigated American alligators', Alligator mississippiensis , response to capture and release (an assumed aversive experience) in coastal resort communities as a model system for understanding wildlife learning in human-dominated landscapes. Our objectives were to investigate whether the degree of human disturbance in the landscape was associated with baseline alligator tolerance of humans or mediated alligators' learning ability. We quantified tolerance using flight initiation trials and estimated learning ability as the response to capture and release using a 'before–after control impact' experimental design. Baseline alligator tolerance did not vary with disturbance, nor did the degree of disturbance impact alligator learning. However, alligators in areas where capture and release occurred were 1.5 times more likely to flee from an approaching human after treatment relative to before. Alligators in control units exhibited similar tolerance to humans over time. Alligator tolerance was also influenced by ambient weather, with alligators least tolerant of humans in cool and cloudy conditions and most tolerant in warm conditions, likely reflecting physiological constraints of ectothermy. While human-dominated landscapes may promote high tolerance of humans through habituation, our findings indicate that high tolerance does not preclude future learning by crocodilians and collectively lend credibility to the use of repeated capture and release as a potential form of aversive conditioning for crocodilians. • We investigated alligators' response to capture–release in human-dominated landscapes. • We examined relations between human disturbance and baseline tolerance and learning. • Baseline tolerance did not vary with disturbance but was influenced by ambient weather. • Alligators were less tolerant of approaching humans after experiencing capture–release. • The degree of landscape level human disturbance did not impact alligator learning. [ABSTRACT FROM AUTHOR]

It is well known that hormones influence and direct most facets of physiology; however, there is still contention regarding the directions of certain relationships, for example, between gonadal hormones and immunity. Among the many proposed relationships relating to gonadal–immune interactions, support for immunosuppressive effects of androgens remains prominent within physiological literature. Although ample study has been directed toward the immunosuppressive effects of androgens, considerable disagreement remains regarding their influence on immune function. In this study, we test the hypothesis that androgens inhibit immunocompetence in the American alligator (Alligator mississippiensis). Developing alligators were incubated at female‐producing temperatures with a subset of individuals being exposed to 17‐α‐methyltestosterone (MT) before sexual determination. 17‐α‐methyltestosterone is a potent androgen, not aromatizable by crocodilians, that has been found to exert masculinizing effects in exposed crocodilian populations in vivo and in vitro. Additionally, a subset of animals was exposed to a novel antigen to quantify innate and acquired immune function. We recovered no significant differences in leukocyte ratios or proportions between groups and found no significant differences in innate immune function as measured by hemolysis‐hemagglutination. However, we did find significant differences in acquired immune function, where masculinized individuals expressed greater antibody titers. Our findings reject the hypothesis that androgens suppress immune function; rather, androgens may be immunoenhancing to acquired humoral responses and neutral to innate humoral immunity in crocodilians. [ABSTRACT FROM AUTHOR]

The anatomy of the archosaurian pelvis and hindlimb has adopted a diversity of successful configurations allowing a wide range of postures during the evolution of the group (e.g., erect, sprawling). For this reason, thorough studies of the structure and function of the pelvic and hindlimb musculature of crocodylians are required and provide the possibility to expand their implications for the evolution of archosaurian locomotion, as well as to identify potential new characters based on muscles and their bony correlates. In this study, we give a detailed description of the pelvic and hindlimb musculature of the South American alligator Caiman yacare, providing comprehensive novel information regarding lower limb and autopodial muscles. Particularly for the pedal muscles, we propose a new classification for the dorsal and ventral muscles of the autopodium based on the organisation of these muscles in successive layers. We have studied the myology in a global background in which we have compared the Caiman yacare musculature with other crocodylians. In this sense, differences in the arrangement of m. flexor tibialis internus 1, m. flexor tibialis externus, m. iliofibularis, mm. puboischiofemorales internii 1 and 2, between Ca. yacare and other crocodylians were found. We also discuss the muscle attachments that have different bony correlates among the crocodylian species and their morphological variation. Most of the correlates did not exhibit great variation among the species compared. The majority of the recognised correlates were identified in the pelvic girdle; additionally, some bony correlates associated with the pedal muscles are highlighted here for the first time. This research provides a wide framework for future studies on comparative anatomy and functional morphology, which could contribute to improving the character definition used in phylogenetic analyses and to understand the patterns of musculoskeletal hindlimb evolution. [ABSTRACT FROM AUTHOR]

Simple Summary: Alligators (Alligator mississippiensis) exhibit unusual immune responses relative to endothermic organisms. For example, most of the highest-expressed liver genes in uninfected mice are related to metabolism. In contrast, the most abundantly expressed hepatic genes expressed in alligators are immune system-oriented. The constraints of endothermy demand a high expression of metabolic genes to maintain temperature and elevated metabolism to support endothermy, while ectothermic alligators reallocate those resources to maintain a highly primed immune system. Injection of alligators with 200× the LD50 of bacterial lipopolysaccharide in mice resulted in no observable biological effects that are observed in endotherms. In addition, treatment with live bacteria caused a decrease in metabolic rate, which again, is the opposite of that exhibited by endotherms. The decrease in oxygen consumption was not accompanied by changes in heart rate or respiration, and thus could not be attributed to bradycardia or bradypnea. Injection of alligators with bacteria caused a complete elimination of digestive tract contents within a few hours. We interpret these activities as temporary minimization of other biological systemic activities to redirect and devote energy to immune function. The reallocation of resources within an organism to fight infection without increases in metabolic rate has not been described in other animals. Uninfected alligators (Alligator mississippiensis) exhibited high constitutive levels of hepatic gene expression related to immune function, whereas the highest-expressed hepatic genes of uninfected mice were related to metabolism. Intraperitoneal challenge of mice with bacterial lipopolysaccharide results in dramatic inflammatory effects including peritoneal ascites, febrile response, dramatic alterations in electrophoretic serum profile, and mortality. In contrast, coelomic injection of alligators with 200× the murine LD50 of intraperitoneal bacterial lipopolysaccharide resulted in no changes in serum protein profiles, behavioral effects, mortality, and no coelomic ascites. However, injection of juvenile alligators with live bacteria resulted in a titer-dependent decrease in metabolic rate, as measured by oxygen consumption. These results are the opposite of those observed for mammalian and avian species. The decreased oxygen consumption was not accompanied by changes in heart or respiration rate, indicating that this phenomenon was not due to bradycardia or bradypnea. Interestingly, challenge of alligators with bacteria resulted in the complete expulsion of digestive tract contents within four hours. We interpret these activities as temporary minimization of other biological systemic activities to redirect and devote energy to immune function. The reallocation of resources within an organism to fight infection without increases in metabolic rate has not been described in other animals. [ABSTRACT FROM AUTHOR]

Purpose: Little is known about the coccidian parasites of the American alligator, Alligator mississippiensis (Daudin). To date, only two species of Eimeria Schneider, 1875 have been previously reported from A. mississippiensis. Here, we report from mensural and morphometric data on two new species of Eimeria from A. mississippiensis from Georgia, USA. Methods: Fresh feces were collected in June 2023 from a single captive juvenile male A. mississippiensis. Multiple samples were placed in individual zip-lock bags and aqueous potassium dichromate was added. They were examined for sporulated oocysts after flotation in Sheather's sugar solution, measured, and photographed. Results: Samples contained oocysts representing two new species of Eimeria. Oocysts of Eimeria tellezae n. sp. are subspheroidal to ellipsoidal with a pitted bi-layered wall, measure (L × W) 34.5 × 31.5 µm, and have a length/width (L/W) ratio of 1.1; a micropyle and polar granule were absent but an oöcyst residuum was present. Sporocysts are ellipsoidal and measure 17.2 × 7.7 µm, L/W 2.2; a nipple-like Stieda body bearing one to several filaments was present but sub-Stieda and para-Stieda bodies were absent. The sporocyst residuum is composed of various-sized granules in a compact rounded or irregular mass, sometimes dispersed between the sporozoites. Oocysts of Eimeria daudini n. sp. are ellipsoidal with a pitted bi-layered wall, measure (L × W) 32.5 × 20.2 µm, and have a length/width (L/W) ratio of 1.6; a micropyle and polar granule were absent but an oöcyst residuum was present. Sporocysts are ellipsoidal and measure 15.4 × 7.4 µm, L/W 2.1; a nipple-like Stieda body bearing one to several filaments was present but sub-Stieda and para-Stieda bodies were absent. The sporocyst residuum is composed of various-sized granules in a compact rounded or irregular mass, sometimes dispersed between the sporozoites. Both new species can readily be distinguished from previously described eimerians from crocodilians, including those from A. mississippiensis. Conclusion: We document two new species of Eimeria from the American alligator. Currently, four species of Eimeria are known from A. mississippiensis examined from both east and west of the Mississippi River, USA. [ABSTRACT FROM AUTHOR]

Simple Summary: The ecological roles and importance of crocodilians (alligators, caiman, crocodiles, gharials) are poorly understood. These large predators are considered to be "ecosystem engineers" because their modification of habitats (e.g., excavation of holes, dens, and tunnels; construction of nests) provides opportunities for vital life activities (e.g., feeding, drinking, breeding, and sheltering) to other wildlife. However, data supporting this contention are scarce for most crocodilian species and, where available, are primarily the result of chance encounters and anecdotal observations; few systematic studies directly focusing on the influence of crocodilian habitat alteration on other wildlife have been conducted. To address this data gap, we monitored American alligator nests with automated game cameras in coastal South Carolina to quantify wildlife visiting nests (faunal associates) and their corresponding behaviors (i.e., how they used nests). From 2016 to 2021, we identified 81 wildlife species at alligator nests, including a wide variety of birds, mammals, reptiles, amphibians, and invertebrates. These animals used alligator nests primarily for feeding/foraging, traveling, and loafing but also basking, burrowing/shelter, breeding, and nesting, and these uses varied by animal group and species. Our results indicate that a diverse assemblage of wildlife uses alligator nest sites in coastal South Carolina for a variety of life activities, and these uses differ among and within animal groups. This study provides a first step for investigations regarding the net impacts of alligator nest-faunal associate interactions and ultimately the greater ecological role of alligators and other crocodilians. Crocodilians are considered to be "ecosystem engineers" because their modification of habitats provides opportunities for feeding, drinking, breeding, and other vital life activities to a wide variety of other animals. One such habitat modification is the construction of nest mounds during the breeding season by most crocodilian species, including American alligators (Alligator mississippiensis). While many reports exist describing wildlife associated with alligator nests, no studies have quantified faunal associates and their corresponding behaviors while visiting nests. To address this data gap, we used automated game cameras to monitor wildlife and their behaviors at alligator nests during the egg incubation period (June–September) in coastal South Carolina, USA (2016–2021). We documented a total of 81 species (79 vertebrates and 2 invertebrates) at 78 alligator nests representing six taxonomic groups, including 48 birds (59.2%), 9 mammals (11.1%), 19 reptiles (23.4%), 3 amphibians (3.7%), 1 malacostracan (1.2%), and 1 insect (1.2%). Collectively, faunal associates primarily used alligator nests for feeding/foraging (51.8%), traveling (29.3%), and loafing (19.9%) and to a much lesser extent basking, burrowing/shelter, breeding, and nesting. However, trends in alligator nest use varied among faunal associate groups (birds, mammals, reptiles, amphibians, etc.), subgroups (e.g., passerines, raptors, wading birds, and waterfowl), and species. Several novel behaviors by some nest associates were also noted during the study, including the first observations of Virginia oppossum (Didelphis virginiana) opening and predating nests, bobcat (Lynx rufus) consuming alligator hatchlings, and Carolina wren (Thryothorus ludovicianus) feeding on the contents of a recently predated alligator egg. The results of this study indicate that a diverse assemblage of vertebrates (and some invertebrates) use alligator nest sites in coastal South Carolina for a variety of life activities during the egg incubation period, and the proportion of the behaviors exhibited varies among animal groups and species. This study provides a first step for investigations regarding the net impacts of alligator nest-faunal associate interactions and ultimately the greater ecological role of alligators and other crocodilians. [ABSTRACT FROM AUTHOR]

Maternal provisioning and the developmental environment are fundamental determinants of offspring traits, particularly in oviparous species. However, the extent to which embryonic responses to these factors differ across populations to drive phenotypic variation is not well understood. Here, we examine the contributions of maternal provisioning and incubation temperature to hatchling morphological and metabolic traits across four populations of the American alligator (Alligator mississippiensis), encompassing a large portion of the species' latitudinal range. Our results show that whereas the influence of egg mass is generally consistent across populations, responses to incubation temperature show population‐level variation in several traits, including mass, head length, head width, and residual yolk mass. Additionally, the influence of incubation temperature on developmental rate is greater at northern populations, while the allocation of maternal resources toward fat body mass is greater at southern populations. Overall, our results suggest that responses to incubation temperature, relative to maternal provisioning, are a larger source of interpopulation phenotypic variation and may contribute to the local adaptation of populations. [ABSTRACT FROM AUTHOR]

The crocodilians include true crocodiles, alligators, caimans, and gharial, and the trade of crocodilian products is regulated in accordance with the Convention of Wild Fauna and Flora (CITES). Hong Kong does not have her own wild crocodilians; thus, all crocodilians meat available is presumably imported with proper license. Here, we obtained a dataset of cytochrome oxidase I (COI) gene markers of 114 crocodilian meat samples (including frozen and dried crocodilian meat products) available in the contemporary market. We have also validated these barcodes in a phylogenetic approach with other data deposited on the GenBank, and detected 112 samples belonging to four crocodile species Crocodylus siamensis, C. porosus, C. niloticus and Alligator mississippiensis, and 2 samples belonging to snake Malayopython reticulatus. The dataset generated in this study will be useful for further studies including meat inspection, illegal trading, and enhancement of international and local legislations on illegal reptile importation. [ABSTRACT FROM AUTHOR]

Identity cues in animal calls are essential for conspecific vocal individual recognition. Some acoustically active species mainly show reliable identity cues in their vocalizations because of variation in anatomy and life history. Long and strenuous-to-produce vocalizations may be particularly effective for showing identity cues because sustaining such calls may reveal individual anatomical differences in sound production. It is largely unknown whether reptiles possess acoustic individuality despite some groups being vocal. We analysed 814 bellows from 47 American alligators, Alligator mississippiensis , extracting spectral characteristics and manually corrected contours of the fundamental frequency. Recognition was up to 66% correct with a supervised classifier (random forest) and 61% with unsupervised clustering (chance = 2.1%), indicating that individual alligators have highly distinct bellows. Alligators were distinguished primarily based on the call spectrum, fundamental frequency contour and amplitude modulation, which also provided information about the animal's size. Neither manual supervision of acoustic analyses nor supervised training on labelled data was necessary to achieve reasonable accuracy, which has promising potential for identification of individuals via passive acoustic monitoring for research and conservation purposes. Additionally, our results highlight the importance of studying the utilization of acoustic individuality in the social lives of crocodylians. • The bellows of American alligators are highly individually distinct. • Classification algorithms can identify American alligators based on their bellows. • Acoustic individuality likely comes from anatomical differences between individuals. • This analytical method has potential for passive acoustic monitoring of Crocodylians. • Crocodylians may utilize such acoustic individuality in their social lives. [ABSTRACT FROM AUTHOR]

Simple Summary: A significant issue in American alligator (Alligator mississippiensis) farming is the high rate of early embryonic deaths among captive eggs. Differences in fatty acid composition between wild and captive eggs have been noted, potentially due to maternal diets. A study was conducted at Golden Ranch using captive breeding alligators fed a specialized diet, supplemented with crawfish waste products. Results showed successful reproductive performance. The breeding females consistently achieved high hatch rates, and the resulting hatchlings exhibited comparable strength and size to their wild counterparts. This suggests that A. mississippiensis can be farmed effectively using captive breeders raised from artificially incubated wild eggs. Historically, there has been little success with the captive breeding of American alligators (Alligator mississippiensis) for both commercial and conservative purposes. This study, conducted at Golden Ranch in Gheens, LA, between 2016 and 2022, utilized a newly formulated commercial feed and practical dietary supplementation (crawfish waste products) to enhance egg production, fertility, and hatch rates. The primary focus of this study was to compare the outcome of this captive breeding program at Golden Ranch with a program conducted at Rockefeller Refuge (RR) between 1979 and 1984. Notable success was achieved in terms of reproductive performance in comparison to the captive breeding program conducted at Rockefeller Refuge. In this study, 16.1 hatchlings were produced per nest on Golden Ranch from captive breeders. Additionally, when wild nests from Golden Ranch were incubated in the same controlled environmental chambers, they produced an average of 16.3 hatchlings per nest. This comparison emphasizes the similarity in egg production between captive-bred A. mississippiensis and their wild counterparts. The findings of this study suggest that a closed farming system for A. mississippiensis can be established by employing captive breeders derived from artificially incubated wild eggs. Furthermore, American alligators raised in controlled environmental chambers during their initial three years of life demonstrated adaptability to captive conditions and tolerated stocking rates associated with farming conditions and served as breeding stock. [ABSTRACT FROM AUTHOR]

Unlike the majority of sauropsids, which breathe primarily through costal and abdominal muscle contractions, extant crocodilians have evolved the hepatic piston pump, a unique additional ventilatory mechanism powered by the diaphragmaticus muscle. This muscle originates from the bony pelvis, wrapping around the abdominal viscera, extending cranially to the liver. The liver then attaches to the caudal margin of the lungs, resulting in a sub-fusiform morphology for the entire "pulmo-hepatic-diaphragmatic" structure. When the diaphragmaticus muscle contracts during inspiration, the liver is pulled caudally, lowering pressure in the thoracolumbar cavity, and inflating the lungs. It has been established that the hepatic piston pump requires the liver to be displaced to ventilate the lungs, but it has not been determined if the lungs are freely mobile or if the pleural tissues stretch ventrally. It has been hypothesized that the lungs are able to slide craniocaudally with the liver due to the smooth internal ceiling of the thoracolumbar cavity. We assess this through ultrasound video and demonstrate quantitatively and qualitatively that the pulmonary tissues are sliding craniocaudally across the interior thoracolumbar ceiling in actively ventilating live juvenile, subadult, and adult individuals (n=7) of the American alligator (Alligator mississippiensis) during both natural and induced ventilation. The hepatic piston is a novel ventilatory mechanism with a relatively unknown evolutionary history. Questions related to when and under what conditions the hepatic piston first evolved have previously been left unanswered due to a lack fossilized evidence for its presence or absence. By functionally correlating specific characters in the axial skeleton to the hepatic piston, these osteological correlates can be applied to fossil taxa to reconstruct the evolution of the hepatic piston in extinct crocodylomorph archosaurs. [ABSTRACT FROM AUTHOR]

Body condition is used as an indicator of the degree of body fat in an animal but evidence of its actual relationship with health diagnostics (e.g., blood parameters) is usually lacking across species. In American alligators (Alligator mississippiensis), body condition has been used as a performance metric within the Greater Everglades ecosystem to provide insight on hydrological and landscape changes on alligator populations. However, there is no clear evidence that spatial body condition changes relate to different health conditions (low food intake vs sickness) and whether this link can be made when relating body condition values with blood parameters. We assessed the relationship between alligator body condition and 36 hematological and biochemistry (blood) parameters in four areas across two physiographic regions (Everglades and Big Cypress) of the Greater Everglades (sample size = 120). We found very strong to weak evidence of linearity between 7 (Big Cypress) and 19 (Everglades) blood parameters and relative condition factor index, from which cholesterol (38%) and uric acid (41%) for the former and phosphorus (up to 52%) and cholesterol (up to 45%) for the latter (mean absolute error MAE = 0.18 each) were the predictors that individually explain most of the body condition variation. The best combination of blood parameters for the Everglades were cholesterol, phosphorus, osmolality, total protein, albumin, alpha 2, beta, and gamma globulins, and corticosterone accounting for 40% (37 ± 21%, MAE = 0.16) of the variation found in alligator body condition for this region. We found better predictability power in models when analyzed at smaller rather than larger scales showing a potential habitat effect on the body condition—blood parameters relationship. Overall, Everglades alligators in poorer condition are likely dehydrated or have an inadequate diet and the spatial differences found between physiographic regions suggest that these areas differ in prey availability/quality. [ABSTRACT FROM AUTHOR]

In Alligator mississippiensis the spinal dura is surrounded by a venous sinus; pressure waves can propagate in the spinal venous blood, and these spinal venous pressures can be transmitted to the spinal cerebrospinal fluid (CSF). This study was designed to explore pressure transfer between the spinal venous blood and the spinal CSF. At rest the cardiac-related CSF pulsations are attenuated and delayed, while the ventilatory-related pulsations are amplified as they move from the spinal venous blood to the spinal CSF. Orthostatic gradients resulted in significant alterations of both cardiac- and ventilatory-related CSF pulsations. Manual lateral oscillations of the alligator's tail created pressure waves in the spinal CSF that propagated, with slight attenuation but no delay, to the cranial CSF. Oscillatory pressure pulsations in the spinal CSF and venous blood had little influence on the underlying ventilatory pulsations, though the same oscillatory pulsations reduced the ventilatory- and increased the cardiac-related pulsations in the cranial CSF. In Alligator the spinal venous anatomy creates a more complex pressure relationship between the venous and CSF systems than has been described in humans. [ABSTRACT FROM AUTHOR]

This protocol describes a minimally invasive surgical technique and approach to successfully examine the gonads of live female American alligators as part of a reproductive examination used in conservation medicine and biology. Best practices are based on examination of over 80 American alligators in the last two years adapting principles derived from other reptilian megafauna species. This protocol is designed for appropriately qualified veterinarians and biologists working in the field. We show likely reproductive tract presentations with respect to breeding status and environmental cues to help guide interpretation of observations. The laparoscopic approach and findings presented here provide tools to safely clinically examine animals in a welfare-oriented way that will advance our understanding of crocodilian reproduction. This technique has not previously been described in this species. [ABSTRACT FROM AUTHOR]

Simple Summary: The skin of American alligators became lighter when animals were exposed to light colored environments. This change occurred over 2–3 months, and was caused by increased pigmented cells in the dermal layers of the skin. Alligators hatch with bright vertical yellow and black stipes that presumably function as camouflage in emergent vegetation. However, the yellow stripes gradually fade/darken until alligators become a homogenous dark gray/black color as adults. Because alligators live in more temperate climates than other crocodilians, we propose that the loss of yellow stripes might help alligators thermoregulate more efficiently during colder months. We measured the brightness of stripes on wild alligators of a broad spectrum of sizes from three different latitudinal locations within their natural range: northern (South Carolina), central (south Louisiana/southeast Texas), and southern (South Florida). The alligators in South Carolina lost stripes faster as they grew larger, while the alligators in the middle portion of the range became darker at a slower rate, and animals in south Florida lost their stripes at an even slower rate. The loss of stripes at different rates might allow alligators to be more efficient at thermal regulation in the different areas that they inhabit. To assess skin color change in alligators, we maintained animals in differently lighted environments and also measured skin colors in an ontogenetic series of wild animals. Juvenile alligators maintained in black enclosures exhibited a gradual lightening of skin color when shifted to white enclosures, and these observed changes were reversible. A histological examination of the skins of alligators maintained in dark tanks showed that the dermis exhibited a dense layer of pigmented cells, while samples from the same animals in light environments exhibited a more diffuse pigmented layer. As alligators grow, they exhibit an ontogenetic loss of stripes that may aid in crypsis and predation. Hatchlings have intense black and yellow vertical stripes that darken with age; adults are a more homogenous black/gray color. Since alligators live in temperate climates and adults have lower surface area/volume ratios, which can be detrimental for the absorption of radiant energy, the darker color of larger animals may also aid in thermoregulation. Alligators at the northern end of their range, with colder climates, exhibited darker skin tones, and the ontogenetic extinction of stripes occurred at a more accelerated rate compared to animals in southern, warmer regions, supporting the idea that latitude-dependent ontogenetic color shift has a role in thermoregulation. [ABSTRACT FROM AUTHOR]

Background: To the authors' knowledge, this is the first report fully describing the surgical and medical management of otitis media and otitis externa in the koala (Phascolarctos cinereus) treated by total ear canal ablation and lateral bulla osteotomy. Case Report: An adult male koala captured as part of a monitoring project in South East Queensland was diagnosed with chlamydial cystitis. Purulent discharge from the right ear was also observed; diagnostic imaging was consistent with otitis media and otitis externa. Yokenella regensburgei was repeatedly cultured from the site. Clinical signs resolved with topical antibiotic therapy; however, recrudesced following cessation of antibiotics. A total ear canal ablation and lateral bulla osteotomy was performed, followed by an extended period of systemic antibiotic therapy. Mild facial nerve paresis was observed for 4 weeks postoperatively and resolved spontaneously. The koala remained clinically healthy for the 6 months it was monitored following release. Conclusion: Total ear canal ablation combined with lateral bulla osteotomy appears to be an appropriate surgical intervention for otitis media combined with otitis externa refractory to medical management in the koala. Transient postoperative facial nerve paresis is a possible complication, as documented in other species. To the authors' knowledge this is the first case of Yokenella regensburgei infection outside of humans and American alligators (Alligator mississippiensis); the clinical significance of this pathogen in the koala remains unknown. [ABSTRACT FROM AUTHOR]

Many ectotherms rely on temperature cues experienced during development to determine offspring sex. The first descriptions of temperature‐dependent sex determination (TSD) were made over 50 years ago, yet an understanding of its adaptive significance remains elusive, especially in long‐lived taxa.One novel hypothesis predicts that TSD should be evolutionarily favoured when two criteria are met—(a) incubation temperature influences annual juvenile survival and (b) sexes mature at different ages. Under these conditions, a sex‐dependent effect of incubation temperature on offspring fitness arises through differences in age at sexual maturity, with the sex that matures later benefiting disproportionately from temperatures that promote juvenile survival.The American alligator (Alligator mississippiensis) serves as an insightful model in which to test this hypothesis, as males begin reproducing nearly a decade after females. Here, through a combination of artificial incubation experiments and mark‐recapture approaches, we test the specific predictions of the survival‐to‐maturity hypothesis for the adaptive value of TSD by disentangling the effects of incubation temperature and sex on annual survival of alligator hatchlings across two geographically distinct sites.Hatchlings incubated at male‐promoting temperatures (MPTs) consistently exhibited higher survival compared to those incubated at female‐promoting temperatures. This pattern appears independent of hatchling sex, as females produced from hormone manipulation at MPT exhibit similar survival to their male counterparts.Additional experiments show that incubation temperature may affect early‐life survival primarily by affecting the efficiency with which maternally transferred energy resources are used during development.Results from this study provide the first explicit empirical support for the adaptive value of TSD in a crocodilian and point to developmental energetics as a potential unifying mechanism underlying persistent survival consequences of incubation temperature. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

We designed a series of studies to investigate whether hypoxia (10% O2) from 20% of incubation to hatching, or from 20 to 50% of incubation, affects cardiovascular function when juvenile American alligators reached an age of 4–5 years compared to juveniles that were incubated in 21% O2. At this age, we measured blood flows in all the major arteries as well as heart rate, blood pressure, and blood gases in animals in normoxia and acute hypoxia (10% O2 and 5% O2). In all three groups, exposure to acute hypoxia of 10% O2 caused a decrease in blood O2 concentration and an increase in heart rate in 4–5-year-old animals, with limited effects on blood flow in the major outflow vessels of the heart. In response to more acute hypoxia (5% O2), where blood O2 concentration decreased even further, we measured increased heart rate and blood flow in the right aorta, subclavian artery, carotid artery, and pulmonary artery; however, blood flow in the left aorta either decreased or did not change. Embryonic exposure to hypoxia increased the threshold for eliciting an increase in heart rate indicative of a decrease in sensitivity. Alligators that had been incubated in hypoxia also had higher arterial PCO2 values in normoxia, suggesting a reduction in ventilation relative to metabolism. [ABSTRACT FROM AUTHOR]

Soybean meal based diets have been suggested to cause gastrointestinal issues in certain species when used as a protein alternative. Using a randomized design, we tested 1,728 alligators in one of 13 communal pens offered one of two diets (seven pens (n = 928) of soybean-based protein diets and six pens (n = 800) of animal-based protein diets) to determine if soybeans would negatively affect the growth, hide quality, behavior and health, when compared with an otherwise identical diet using animal-based protein. Both feeds were nearly identical in composition for protein and fat percentages and identical for all minerals and elements. Crude protein was a minimum of 50%, crude fat a minimum of 12%, crude fiber a minimum of 4%, and phosphorous was maintained at 1%. From this information we estimated the One Welfare of using soy as a protein in commercial diets. Although there was a statistically significant decrease in belly width (p = 0.0009; harvested hide size) for alligators fed soybean-based protein diets, all other measured parameters of soybean vs. animal-based protein diets were comparable, suggesting this environmentally sustainable alternative protein source warrants consideration as a feed base. Weight was not significantly different suggesting either diet would yield similar volumes of meat. Total length was significantly affected by diet. Hide quality was not negatively impacted by protein type, with both diets producing high quality hides free of defects (assessed at the salted hide stage prior to tanning). Behaviors were not influenced by the feed type, with animals fed either diet using the pen structures the same. Further, feeding times were the same suggesting the soybean-based protein diet was equally easy to eat and palatable as the animal-based protein diet. Behavior and feeding suggested soy-based diets do not alter time budgets or activities. There were no differences in the frequency or severity of pathologies for animals fed either diet. Respiratory (lung and trachea as a proxy to measure dust inhalation), gastrointestinal (small intestine as a proxy to measure digestive disturbances), and renal (kidney as a proxy for excretory stress) histopathology demonstrated neither diet was causing overt problems. One Welfare conclusions were feeding a soybean-based protein diet did not cause production or welfare issues. Further, soybean protein-based diets may be an environmentally sustainable alternative to currently used animal-based diets. Research examining different soybean protein concentrations and sources is warranted. [ABSTRACT FROM AUTHOR]

Human‐driven land use change can fundamentally alter ecological communities, especially the diversity and abundance of large‐bodied predators. Yet, despite the important roles large‐bodied predators play in structuring communities through feeding, there have been only a few investigations of how the feeding patterns of large‐bodied predators change in human‐dominated landscapes. One group of large‐bodied predators that has been largely overlooked in the context of land use change is the crocodilians. To help fill these gaps, we studied the feeding patterns of juvenile American alligators (Alligator mississippiensis) on neighboring barrier islands on the southeast coast of Georgia, USA. Jekyll Island has multiple golf courses and substantial amounts of human activity, while Sapelo Island does not have any golf courses and a much smaller amount of human activity. We found that juvenile alligator populations on both islands ate the same types of prey but in vastly different quantities. Sapelo Island alligators primarily consumed crustaceans while alligators that lived on Jekyll Island's golf courses ate mostly insects/arachnids. Furthermore, the Jekyll Island alligators exhibited a much more generalist feeding pattern (individuals mostly ate the same types of prey in the same quantities) than the more specialized Sapelo Island alligators (diets were more varied across individuals). The most likely explanation for our results is that alligators living on golf courses have different habitat use patterns and have access to different prey communities relative to alligators in more natural habitats. Thus, land use change can strongly alter the feeding patterns of large‐bodied predators and, as a result, may affect their body condition, exposure to human‐made chemicals, and role within ecological communities. [ABSTRACT FROM AUTHOR]

Scaling of body shape, gait, limb kinematics, and kinetics can inform about mechanical and energetic constraints influencing animal locomotion on land. However, our knowledge of terrestrial locomotion among tetrapods is biased toward animals that use parasagittal limb postures (mammals and birds). Whether species that use non-parasagittal limb postures (e.g. crocodylians and lizards) share similar scaling principles remains uncertain, especially toward the larger end of the body size spectrum. Here, we compare new data from large adult American alligators (140–223 kg) with previous data from smaller individuals (0.2–5.6 kg) to evaluate the scaling of gait, limb posture, ground reaction forces, and inertial properties of body segments over a size range spanning three orders of magnitude. Larger alligators walked with higher relative stride frequencies and shorter relative stride lengths at equal dimensionless speeds, suggesting that alligators prioritize stance phase mechanical work reduction at the expense of higher costs for swing as they increase in size. Limb posture also changed with body mass: ∼1 kg and larger alligators typically used more adducted and extended limbs, which is expected to mitigate limb muscle forces during stance. Ground reaction forces were increasingly hindlimb dominant as alligators grow to larger size, paralleled by a posterior shift in the center of mass. Counterintuitively, the forelimb grew faster in mass than the hindlimb, possibly because recruited muscle volume is closer to its maximum capacity in the forelimb, compelling larger alligators to keep up with increased mechanical demands via muscle growth more for the forelimb than the hindlimb. These results highlight the numerous changes in body proportions and locomotor performance that are required among animals that use non-parasagittal limb posture, as they grow from neonatal sizes into large adults. [ABSTRACT FROM AUTHOR]

Ursus americanus (American Black Bear) and Alligator mississippiensis (American Alligator) are sympatric in areas of Florida. During summer, alligators build nest mounds for eggs on freshwater shores, shallow marshes, and tree islands. Biologists have speculated that bears might prey upon alligator nests because of their opportunistic and generalist diet, though such predation in Florida has not been documented in peer-reviewed literature. Herein, we report 3 photographed events of American Black Bear predation on American Alligator nests in Everglades National Park, Big Cypress National Preserve, and Dinner Island Ranch Wildlife Management Area, FL. During each event, bears dug into alligator nests and consumed egg contents. The predation events varied in duration from 36 minutes to nearly 5 hours. During 1 event, a female bear consumed alligator eggs alongside 2 cubs of the year. Future research might explore the extent and effect of nest predation on American Alligator populations and the benefits to American Black Bears. [ABSTRACT FROM AUTHOR]

Soybean meal based diets have been suggested to cause gastrointestinal issues in certain species when used as a protein alternative. Using a randomized design, we tested 1,728 alligators in one of 13 communal pens offered one of two diets (seven pens (n = 928) of soybean-based protein diets and six pens (n = 800) of animal-based protein diets) to determine if soybeans would negatively affect the growth, hide quality, behavior and health, when compared with an otherwise identical diet using animal-based protein. Both feeds were nearly identical in composition for protein and fat percentages and identical for all minerals and elements. Crude protein was a minimum of 50%, crude fat a minimum of 12%, crude fiber a minimum of 4%, and phosphorous was maintained at 1%. From this information we estimated the One Welfare of using soy as a protein in commercial diets. Although there was a statistically significant decrease in belly width (p = 0.0009; harvested hide size) for alligators fed soybean-based protein diets, all other measured parameters of soybean vs. animal-based protein diets were comparable, suggesting this environmentally sustainable alternative protein source warrants consideration as a feed base. Weight was not significantly different suggesting either diet would yield similar volumes of meat. Total length was significantly affected by diet. Hide quality was not negatively impacted by protein type, with both diets producing high quality hides free of defects (assessed at the salted hide stage prior to tanning). Behaviors were not influenced by the feed type, with animals fed either diet using the pen structures the same. Further, feeding times were the same suggesting the soybean-based protein diet was equally easy to eat and palatable as the animal-based protein diet. Behavior and feeding suggested soy-based diets do not alter time budgets or activities. There were no differences in the frequency or severity of pathologies for animals fed either diet. Respiratory (lung and trachea as a proxy to measure dust inhalation), gastrointestinal (small intestine as a proxy to measure digestive disturbances), and renal (kidney as a proxy for excretory stress) histopathology demonstrated neither diet was causing overt problems. One Welfare conclusions were feeding a soybean-based protein diet did not cause production or welfare issues. Further, soybean protein-based diets may be an environmentally sustainable alternative to currently used animal-based diets. Research examining different soybean protein concentrations and sources is warranted.

Plasma biochemistry values represent a crucial and minimally invasive tool for evaluating nutritional and physiological condition of the animal. Biochemical data provides valuable information in those species exposed to environmental stressors. In this study, we aimed to apply for the first time micro‐volume plasma tests to measured total plasma protein, albumin, and glucose in juvenile Caiman latirostris and to compare our results with other studies reporting crocodilian biochemistry values. We found that caimans from heat treatment were heavier, longer and had higher levels of glucose than those from the control group. Conversely, food restricted caimans had less growth, body condition and had 32.1% lower albumin concentrations than those from the control group. While no significant differences were observed in any parameters measured from water restricted caimans compared with control group. The values obtained for each of the biochemical determinations were lower than those previously reported for adult of C. latirostris, but similar finding for protein concentration compared with Alligator mississippiensis. Micro technique offers the advantage of increasing information and at the same time a greater physiological understanding of the crocodilians species. Research highlights: This is the first report that apply micro technique for measured biochemical analytes of plasma of juvenile Caiman latirostris.Total protein, albumin and glucose concentrations in juvenile caimans were lower than those previously reported for adults of Caiman latirostris. [ABSTRACT FROM AUTHOR]

To resist forward displacement of their body during non-locomotor behaviors such as feeding, American alligators (Alligator mississippiensis) hold their hindfeet vertical, then push the foot into the substrate so that the dorsum of the foot forms a contact area with the substrate. Herein this form of bracing is termed pedal anchoring. The purpose of the present study was to describe pedal anchoring and to demonstrate whether it entailed interaction between the hindfoot (pes) of Alligator and the substrate that differed from the interactions seen during locomotion. Alligator tracks were studied in the wild, during controlled field trials, and on a mud trackway in the laboratory; in each setting locomotor and pedal anchoring tracks were photographed, cast in Plaster of Paris, then features of the casts quantified. Statistical analysis demonstrated greater variation in the wild tracks, presumably reflecting the larger size and velocity ranges of the alligators involved, and suggested that the mud trackway used during the locomotor trials did not create significant artifact. Tracks produced during locomotion and pedal anchoring by the same alligators, on the same substrate, yielded significantly different quantitative features, different matrices of Pearson correlation coefficients, and different patterns of character distribution following Principal Component Analysis. These results all support the conclusion that pedal anchoring involves fundamentally different interaction between the pes and the substrate than occurs during locomotion. [ABSTRACT FROM AUTHOR]

Blood was collected from alligators at a large alligator farm in Louisiana to compare stress levels to those in wild alligators. The measurement of corticosterone (CORT) levels and heterophil/lymphocyte ratios were used to assess stress levels because both parameters become elevated during periods of physiological stress. We compared CORT concentrations and H/L ratios in wild animals that were either the same size or the same age class as farmed alligators. Plasma CORT levels and H/L ratios were no higher than those in wild alligators. To ensure consistent results across the farm, we compared plasma hormone concentrations in animals of the same size classes maintained in different enclosures and also in different buildings and found no differences. We believe that results such as these obtained from independent laboratories can be used as evidence for regulatory agencies that crocodylian farms raise their animals in low stress environments under Best Management Practices guidelines. [ABSTRACT FROM AUTHOR]

The potential for animals to modify spatial patterns of nutrient limitation for autotrophs and habitat availability for other members of their communities is increasingly recognized. However, net trophic effects of consumers acting as ecosystem engineers remain poorly known. The American Alligator Alligator mississippiensis is an abundant predator capable of dramatic modifications of physical habitat through the creation and maintenance of pond‐like basins, but its role in influencing community structure and nutrient dynamics is less appreciated.We investigated if alligators engineer differences in nutrient availability and changes to community structure by their creation of 'alligator ponds' compared to the surrounding phosphorus (P)‐limited oligotrophic marsh.We used a halo sampling design of three distinct habitats extending outward from 10 active alligator ponds across a hydrological gradient in the Everglades, USA. We performed nutrient analysis on basal food‐web resources and quantitative community analyses, and stoichiometric analyses on plants and animals.Our findings demonstrate that alligators act as ecosystem engineers and enhance food‐web heterogeneity by increasing nutrient availability, manipulating physical structure and altering algal, plant and animal communities. Flocculent detritus, an unconsolidated layer of particulate organic matter and soil, showed strong patterns of P enrichment in ponds. Higher P availability in alligator ponds also resulted in bottom‐up trophic transfer of nutrients as evidenced by higher growth rates (lower N:P) for plants and aquatic consumers. Edge habitats surrounding alligator ponds contained the most diverse communities of invertebrates and plants, but low total abundance of fishes, likely driven by high densities of emergent macrophytes. Pond communities exhibited higher abundance of fish compared to edge habitat and were dominated by compositions of small invertebrates that track high nutrient availability in the water column. Marshes contained high numbers of animals that are closely tied to periphyton mats, which were absent from other habitats.Alligator‐engineered habitats are ecologically important by providing nutrient‐enriched 'hotspots' in an oligotrophic system, habitat heterogeneity to marshes, and refuges for other fauna during seasonal disturbances. This work adds to growing evidence that efforts to model community dynamics should routinely consider animal‐mediated bottom‐up processes like ecosystem engineering. [ABSTRACT FROM AUTHOR]

American alligators (Alligator mississippiensis) are native to freshwater habitats in the Southeastern United States. These areas are susceptible to salinity increases due to extreme weather events (e.g., hurricanes) and climate change. The goal of this study was to investigate behaviors in juvenile alligators exposed to 12‰ saltwater for five weeks. Sixteen alligators were maintained in an experimental tank with 90 L of water and a heat lamp overhanging a basking plate. Observations were conducted in freshwater (prior to exposure to saltwater) and over the course of 5 weeks in 12‰ saltwater. This allowed for comparison of behaviors in freshwater and in saltwater in the same group of animals. Behaviors related to thermoregulation (basking and staying in the water) and feeding were recorded via instantaneous sampling, in which sampling intervals of 1 min occurred throughout a 20 min observation period. Saltwater-exposed alligators reduced foraging and feeding within the first week of saltwater exposure and spent significantly less time basking compared with freshwater observations. Furthermore, significantly fewer animals chose to bask over the course of 5 weeks in saltwater. A novel behavior, never seen in freshwater, was the closing of the outer eyelids when alligators were in the saltwater. Collectively, the present study demonstrates that chronic saltwater exposure has significant impact on the thermoregulatory behavior in juvenile alligators concomitantly exposed to dehydration and salt-loading without access to freshwater. As alligator hatchlings emerge during peak hurricane season, the survivability of hatchlings may be compromised if access to freshwater is unattainable.

Major transformations in the locomotor system of archosaurs (a major clade of reptiles including birds, crocodiles, dinosaurs, and pterosaurs) were accompanied by significant modifications to ankle anatomy. How the evolution of such a complex multi‐joint structure is related to shifts in ankle function and locomotor diversity across this clade remains unclear and weakly grounded in extant experimental data. Here, we used X‐ray Reconstruction of Moving Morphology to reconstruct skeletal motion and quantify the sources of three‐dimensional ankle mobility in the American alligator, a species that retains the ancestral archosaur ankle structure. We then applied the observed relationships between joint excursion and locomotor behaviors to predict ankle function in extinct archosaurs. High‐resolution reconstructions of Alligator skeletal movement revealed previously unseen regionalized coordination among joints responsible for overall ankle rotation. Differences in joint contributions between maneuvers and steady walking parallel transitions in mobility inferred from the ankle structure of fossil taxa in lineages with more erect hind limb postures. Key ankle structures related to ankle mobility were identified in the alligator, which permitted the characterization of ancestral archosaur ankle function. Modifications of these structures provide morphological evidence for functional convergence among sublineages of bird‐line and crocodylian‐line archosaurs. Using the dynamic insight into the internal sources of Alligator ankle mobility and trends among locomotor modes, we trace anatomical shifts and propose a mechanistic hypothesis for the evolution of ankle structure and function across Archosauria. [ABSTRACT FROM AUTHOR]

Burmese pythons (Python bivittatus Kuhl, 1820) are one of the world's largest snake species, making them a highly successful and biologically damaging invasive predator in the Greater Everglades Ecosystem, Florida, USA. Though we have knowledge of python diet within this system, we understand very little of other interactions with native species. Effects native species have on invasive pythons, especially in the juvenile size class, are of particular interest as the prevalence of mortalities would inform potential population growth and trophic dynamics with native prey species. Native ophiophagous predators in Florida feed on smaller native snake species and it is unknown if they consistently recognize similarly sized juvenile invasive pythons as prey items. Using radiotelemetry, we found at least four native species within Big Cypress National Preserve that were implicated in juvenile python deaths, including three Florida cottonmouths (Agkistrodon conanti Gloyd, 1969), five American alligators (Alligator mississippiensis Daudin, 1802), one hispid cotton rat (Sigmodon hispidus Say and Ord, 1825), and three mesomammals. One mortality was the result of an attempt to subdue a prey item 106% the size of the python, constituting the largest predator:prey size ratio ever reported in this size class. This finding may indicate that phenotypic variation in individual juvenile pythons includes behavior that could be maladaptive within the novel Florida environment. Here we describe some of the first confirmed cases of non-anthropogenic mortality in juvenile Burmese pythons in Florida and present evidence that invasive pythons in this size class are now being incorporated into the diets of native species in its invasive range. [ABSTRACT FROM AUTHOR]

Crocodilians are considered to be “ecosystem engineers” because their modification of habitats provides opportunities for feeding, drinking, breeding, and other vital life activities to a wide variety of other animals. One such habitat modification is the construction of nest mounds during the breeding season by most crocodilian species, including American alligators (Alligator mississippiensis). While many reports exist describing wildlife associated with alligator nests, no studies have quantified faunal associates and their corresponding behaviors while visiting nests. To address this data gap, we used automated game cameras to monitor wildlife and their behaviors at alligator nests during the egg incubation period (June–September) in coastal South Carolina, USA (2016–2021). We documented a total of 81 species (79 vertebrates and 2 invertebrates) at 78 alligator nests representing six taxonomic groups, including 48 birds (59.2%), 9 mammals (11.1%), 19 reptiles (23.4%), 3 amphibians (3.7%), 1 malacostracan (1.2%), and 1 insect (1.2%). Collectively, faunal associates primarily used alligator nests for feeding/foraging (51.8%), traveling (29.3%), and loafing (19.9%) and to a much lesser extent basking, burrowing/shelter, breeding, and nesting. However, trends in alligator nest use varied among faunal associate groups (birds, mammals, reptiles, amphibians, etc.), subgroups (e.g., passerines, raptors, wading birds, and waterfowl), and species. Several novel behaviors by some nest associates were also noted during the study, including the first observations of Virginia oppossum (Didelphis virginiana) opening and predating nests, bobcat (Lynx rufus) consuming alligator hatchlings, and Carolina wren (Thryothorus ludovicianus) feeding on the contents of a recently predated alligator egg. The results of this study indicate that a diverse assemblage of vertebrates (and some invertebrates) use alligator nest sites in coastal South Carolina for a variety of life activities during the egg incubation period, and the proportion of the behaviors exhibited varies among animal groups and species. This study provides a first step for investigations regarding the net impacts of alligator nest-faunal associate interactions and ultimately the greater ecological role of alligators and other crocodilians.

This document is a correction to a study titled "Xenobiotic estradiol‐17ß alters gut microbiota of hatchling American alligators (Alligator mississippiensis)" published in Environmental Microbiology. The correction addresses an error in Figure 2B, where the samples displayed in the published beta diversity plot were not correctly associated with treatment groups. Upon re-analysis, it was found that the bacterial community structure does differ between groups, suggesting that the microbiomes of each treatment group were distinct from one another. The correction does not significantly impact the scientific conclusions of the study. [Extracted from the article]

Mercury is a naturally occurring element but is also considered a widespread contaminant due to global anthropogenic activity. Even in moderate amounts, mercury (Hg) is an established neurotoxin and is associated with a range of adverse outcomes both in humans and wildlife. Humans in the United States are most commonly exposed to Hg through contaminated food or drinking water, and the consumption of game species, particularly those occupying higher trophic levels, has the potential to expose hunters to high concentrations of Hg. In the present study, we determined Hg concentrations in tail muscle and blood from American alligators (Alligator mississippiensis) inhabiting a region (Savannah River Site, SC, USA) with known Hg contamination. We then integrated these data with alligator harvest records and previously published surveys of alligator meat consumption patterns to estimate potential exposure risk. We found that the average Hg concentrations in tail muscle (1.34 mg/kg, wet wt) from sampled alligators exceeded the recommended threshold for Hg exposure based on the World Health Organization's guidelines (0.5 mg/kg, wet wt). In addition, based on regional consumption patterns reported for both adults and children, we estimated Hg exposures (x¯Adult = 0.419 µg/kg/day, x¯Child = 2.24 µg/kg/day) occurring well above the US Environmental Protection Agency methylmercury reference dose of 0.1 μg/kg/day. Although the two reservoirs sampled in the present study are not currently open to alligator hunting, they are connected to waters that are publicly accessible, and the extent of alligator mobility across these sites is not known. Together, the findings reported in the present study further demonstrate the need for active monitoring of Hg concentrations in game species, which can convey substantial exposure risks to the public. Environ Toxicol Chem 2023;42:525–534. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC. [ABSTRACT FROM AUTHOR]

Crocodilians (alligators, crocodiles, and gharials) are the closet living relatives to birds and, as such, represent a key clade to understand the evolution of the avian brain. However, many aspects of crocodilian neurobiology remain unknown. In this paper, we address an important knowledge gap as there are no published studies of cerebellar connections in any crocodilian species. We used injections of retrograde tracers into the cerebellum of the American alligator (Alligator mississippiensis) to describe for the first time the origin of climbing and mossy fiber inputs. We found that inputs to the cerebellum in the American alligator are similar to those of other nonavian reptiles and birds. Retrograde labeled cells were found in the spinal cord, inferior olive, reticular formation, vestibular and cerebellar nuclei, as well as in nucleus ruber and surrounding tegmentum. Additionally, we found no retrogradely labeled cells in the anterior rhombencephalon which suggest that, like other nonavian reptiles, crocodilians may lack pontine nuclei. Similar to birds and other nonavian reptiles, we found inputs to the cerebellum from the pretectal nucleus lentiformis mesencephali. Additionally, we found retrogradely labeled neurons in two nuclei in the pretectum: the nucleus circularis and the interstitial nucleus of the posterior commissure. These pretectal projections have not been described in any other nonavian reptile to date, but they do resemble projections from the nucleus spiriformis medialis of birds. Our results show that many inputs to the cerebellum are highly conserved among sauropsids and that extensive pretectal inputs to the cerebellum are not exclusive to the avian brain. Finally, we suggest that the pontine nuclei of birds are an evolutionary novelty that may have evolved after the last common ancestor between birds and crocodilians, and may represent an intriguing case of convergent evolution with mammals. [ABSTRACT FROM AUTHOR]