Search

Understanding the health of urban animals is key for preventing and controlling zoonotic diseases. To achieve this goal, it’s necessary to understand what factors could have an impact on those animals’ health. Therefore, the aim of this article is to compare some health characteristics of opossums (Didelphis virginiana) in urban environments with and without human presence. For this, we trapped opossums in two urbanized areas: one dominated by buildings and one by roads and parking lots (plus two control locations in natural areas). During two periods: normal activities and under lockdown due to COVID-19 conditions (when the presence of people was minimal). We found that in the building area, human presence has almost no effect on the opossums’ health (with only minor changes in erythrocyte counts and tar coverage); however, in the parking lot, the opossum population dropped drastically because of human activities (use of vehicles). This suggests that human presence is not harmful for those animals, but cars are. Therefore, the use of vehicles has a negative impact on opossums’ health and could increase the spreading of zoonotic diseases. [ABSTRACT FROM AUTHOR]

Simple Summary: In human-dominated areas where top predators no longer occur, interactions among medium-sized predators can be complex, especially when considering how they share space and time based on seasonal changes in food and habitat. We studied this using camera traps placed in various habitats from February 2021 to July 2023, at Fort De Soto County Park, a barrier island complex located in west central Florida. Three species of mammals (coyotes, raccoons, and Virginia opossums) were the most frequently photographed. Our analysis showed that during the wet season, these species were most likely to be photographed in similar habitats and times. During the dry season, when perhaps there were fewer food sources, the species shifted when they were active in a manner that created less overlap. Also in the dry season, opossums made more use of mangrove habitats. Understanding the relationships among these species is important because this area supports nesting shorebirds and sea turtles, known prey for these predators. Due to lack of apex predators in human-dominated landscapes, mesopredator relationships are complex and spatiotemporal niche partitioning strategies can vary, especially when seasonal shifts in resource availability occur. Our objective was to understand spatiotemporal niche overlap across seasons among mesopredators inhabiting a barrier island complex. We placed 19 unbaited cameras throughout Fort De Soto County Park, Florida, USA between February 2021 and July 2023. Of six mesopredator species detected, three species had >75 detections during both the wet and dry seasons (coyote, Canis latrans; Virginia opossum, Didelphis virginiana; and raccoon, Procyon lotor). Using general linear mixed models, we determined that during the wet season coyote–raccoon and raccoon–opossum detections were positively associated with each other (p < 0.05). During the dry season, raccoon–opossum detections were positively associated, and opossums were more likely to be detected around mangroves. After calculating coefficients of overlap, we found all three species varied their temporal activity between seasons. During the dry season exclusively, all three mesopredators occupied different temporal niches. The park's isolated but developed nature has potentially led to a destabilized mesopredator community. Understanding seasonal mesopredator dynamics of Fort De Soto is particularly important because this park supports a high number of nesting shorebirds and sea turtles, which are known food sources for mesopredators. [ABSTRACT FROM AUTHOR]

Rodent carcasses are a source of food and a biological hazard that can commonly be found in natural and anthropic ecosystems. Therefore, this article aims to determine which organisms consume those carcasses in an urban reserve. For this, 53 rodent carcasses were placed in front of camera traps to record their consumers. The final destiny of 41 carcasses is known: 76 % were consumed by opossums (Didelphis virginiana) and 24 % by ringtails (Bassariscus astutus). Flies and ants attempted to take advantage of the carcasses but in all cases ended up losing the competition to mammals. Opossums are the most efficient carrion consumers, as they exhibit learning as to where the carcasses are located and are able to consume old carcasses (up to 10 days old). This suggests that mid-size mammals, especially opossums, are providing an important ecological and health service for both natural ecosystems and human populations by removing rodent carcasses that otherwise could become sources of infection. [ABSTRACT FROM AUTHOR]

Context. Adding an attractant to remote camera traps has become a popular method to increase detections of cryptic carnivores. However, there is ongoing debate about whether this practice can biasthe behaviour and activity patterns of these species. Aims. Our aim wasto determine how using a popular attractant at camera traps could affect carnivore detection probabilities and temporal activity. Methods. We used an experimental design in which we randomly set half of our camera traps on arrays at two sites in western North Carolina with an attractant: canned sardines in oil. Halfway through the survey season, we switched which camera traps had sardines and which did not. We estimated detection probability for each carnivore species observed using occupancy models, and we used kernel density estimations to evaluate changes in diel activity patterns between camera traps with and without an attractant. Key results. We found that when sardines were used at camera traps, detectability of bobcats (Lynx rufus), coyotes (Canis latrans), northern raccoons (Procyon lotor), Virginia opossums(Didelphisvirginiana), and eastern spotted skunks(Spilogale putorius) more than doubled, but there waslittle or no effect on striped skunk (Mephitis mephitis) detectability. Of the species we most frequently detected (coyotes, raccoons, and opossums), activity patterns between camera traps with and without a sardine attractant overlapped moderately to highly, and a significant effect on diel activity patterns was observed only for raccoons. Conclusions. Use of attractants can greatly increase the probability of detecting nearly all carnivores at camera traps. The effects of attractants on diel activity patterns are species-specific, with two of our three most-detected species unaffected by their use, suggesting that attractants can be used to effectively study these behaviours in some carnivore species. Implications. A sardine attractant can increase the detection of many carnivore species, using camera traps, without causing a significant deviation of diel activity patterns, thus allowing for unbiased investigations into most species’ spatio–temporal behaviour in the Appalachian Mountains – and likely other systems. [ABSTRACT FROM AUTHOR]

Instantaneous head posture (IHP) can extensively alter resting hyoid position in humans, yet postural effects on resting hyoid position remain poorly documented among mammals in general. Clarifying this relationship is essential for evaluating interspecific variation in hyoid posture across evolution, and understanding its implications for hyolingual soft tissue function and swallowing motor control. Using Didelphis virginiana as a model, we conducted static manipulation experiments to show that head flexion shifts hyoid position rostrally relative to the cranium across different gapes. IHP-induced shifts in hyoid position along the anteroposterior axis are comparable to in vivo hyoid protraction distance during swallowing. IHP also has opposite effects on passive genio- and stylohyoid muscle lengths. High-speed biplanar videoradiography suggests Didelphis consistently swallows at neutral to flexed posture, with stereotyped hyoid kinematics across different head postures. IHP change can affect suprahyoid muscle force production by shifting their positions on the length-tension curve, and redirecting lines of action and the resultant force from supra- and infrahyoid muscles. We hypothesize that demands on muscle performance may constrain the range of swallowing head postures in mammals. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'. [ABSTRACT FROM AUTHOR]

As human development continues to expand, wildlife must relocate or adapt to survive. Many mammalian mesopredators, such as the Virginia opossum (Didelphis virginiana), have adapted to living alongside human development. Furthermore, top‐down predation pressure may be altered in nuanced ways within the human environment. Species such as opossums may be shielded from predation by human development or behavioral changes in predators. Understanding how dominant and subordinate mesopredators co‐exist across natural and developed areas will provide insight into how wildlife communities are structured. Our objective was to evaluate how opossum occupancy, abundance, and activity were associated with human development and the relative abundance of their predators. We used data from a nationwide camera trapping study, Snapshot USA, to estimate opossum occupancy, abundance, and activity. We related these measures to the surrounding landscape and urbanization variables. We found that opossum occupancy was positively associated with anthropogenic sound (a surrogate for human activity). Furthermore, opossums in heavily forested areas were more likely to be detected in locations with higher predicted anthropogenic sounds. In areas with a high density of human housing, opossum relative abundance increased when predator abundance increased. We also found opossums were strictly nocturnal and shifted their activity to earlier in the evening in the presence of high predator abundance. Our results suggest that humans and their urban development can have multidimensional impacts on opossum behavior and occurrence, and could facilitate changes in predator–prey dynamics. Future research should evaluate if the association of opossums with urban areas is due to human‐subsidized resources or caused by reduced mortality from altered predator–prey dynamics. [ABSTRACT FROM AUTHOR]

ABSTRACT: The aim was to describe the incidence and lesions caused by metazoan and protozoan parasites in Didelphis virginiana opossums in Mexico. From 2019 to 2021, twenty D. virginiana were collected from the state of Colima, Mexico. Post mortem, parasitological, and histopathological studies were performed to identify and describe their lesions and findings. All opossums(20/20) presented at least one type of parasite of the twelve found; the most abundant were nematodes 58.33% (7/12) Didelphostrongylus hayesi, Turgida turgida, Cruzia sp., Viannaia sp., Trichuris didelphis, Trichostrongylidae and Gnathostoma sp. Protozoa 25% (3/12), including Sarcocystis sp., Besnoitia sp., and Sarcocystis sp. A single specimen of Mathevotaenia sp., 8.3% (1/12), and Paragonimus mexicanus 8.3%, were identified (1/12). The most affected systems were the digestive, respiratory, and musculoskeletal. The most abundant parasites were Turgida turgida (20/20) 100%, Cruzia sp., (16/20) 80%, and Viannaia sp. (6/20) 30%, followed by Sarcocystis sp. cysts, (6/20) 30%. The associated parasitic lesions were: D. hayesi produce eosinophilic granulomatous bronchopneumonia, P. mexicanus eosinophilic focal granulomatous pneumonia, and Besnoitia sp., focal eosinophilic lymphoplasmacytic interstitial pneumonia. Gnathostoma and T. turgida caused severe eosinophilic granulomatous focal gastritis. Viannaia sp., Sarcocystis sp., Mathevotaenia sp., and Trichostrongylidae; caused diffuse eosinophilic mucosal enteritis. Cruzia sp., and T. didelphis, induced diffuse eosinophilic mucosal typhlitis. Sarcocystis sp. cysts were detected in the cytoplasm of muscle fibers without histological changes.

Conservation of natural ecosystems embedded in urban contexts is a big challenge because diverse anthropogenic factors continuously impact native biodiversity and ecological processes. One such factor is the pervasive presence of free-ranging predators, especially cats (Felis silvestris catus) and dogs (Canis lupus familiaris), which may severely affect local wildlife. The "Reserva Ecológica del Pedregal de San Ángel" (REPSA), located within the main campus of the Universidad Nacional Autónoma de México (UNAM), in southern Mexico City, is an important natural area that protects a peculiar volcanic spill ecosystem holding native and endemic biodiversity. In 2012, UNAM launched a control program of cats and dogs in REPSA that is still active. To assess the potential impact of cats and dogs on wildlife species, we used live and camera traps coupled with capture-recapture analyses to evaluate changes in the vertebrate community, particularly in the presence and abundance of two medium-size native mammals (Didelphis virginiana and Bassariscus astutus), before (2008–2009) and during (2017–2019) the control program. Results showed that the abundance of dogs decreased between the two periods, but not so the abundance of cats, whereas the native vertebrate diversity increased from the pre-control stage to the control period. Furthermore, we found a negative, non-significant relationship between the abundance of D. virginiana and that of dogs, and a positive, also non-significant relationship between the presence and abundance of B. astutus with the abundance of dogs. We conclude that the control program of free-ranging predators has been beneficial for the conservation of native vertebrates and recommend its continuation and enhancement. [ABSTRACT FROM AUTHOR]

Throughout the eastern United States, the National Rabies Management Program (NRMP) distributes oral rabies vaccine (ORV) baits to manage rabies virus circulation in raccoon (Procyon lotor) populations. The consumption of vaccine baits by non‐target species including Virginia opossums (Didelphis virginiana) may reduce the effectiveness of ORV programs, but competition for baits remains poorly quantified in many areas of the southeastern United States. We distributed placebo ORV baits injected with a biomarker across 4 land cover types (bottomland hardwood, upland pine, riparian, isolated wetland) on the Savannah River Site in South Carolina, USA, 2017–2019. We then trapped and collected whiskers from 247 raccoons and 78 opossums to assess biomarker presence using fluorescent microscopy. Our data revealed greater bait uptake probability by raccoons (estimated x̅ = 0.30, 95% CI = 0.19–0.44) compared to opossums (estimated x̅ = 0.11, 95% CI = 0.05–0.23) across all cover types surveyed. Probability of bait consumption was not affected by cover type or the abundance of raccoons or opossums. Among raccoons, males were more likely to consume baits than females (estimated x̅ = 0.28, 95% CI = 0.17–0.44 for males and 0.14, 95% CI = 0.05–0.31 for females) and probability of consumption increased by 0.08 with each additional day trapped during the 10‐day trapping session. Uptake rates for raccoons were relatively low compared to other studies and not influenced by competition with opossums. These low consumption rates indicate that additional research addressing the roles of baiting season, bait density, and resource selection will be important to maximize ORV bait uptake by target species in these southeastern landscapes. [ABSTRACT FROM AUTHOR]

We developed a venipuncture technique of the ventral caudal vein in conscious Virginia opossums (Didelphis virginiana) in cage traps, enabling blood sampling without anesthesia. Blood samples were successfully collected from all 28 opossums in this study by this technique. Draw volume of <0.1 mL occurred in only four opossums (14%). [ABSTRACT FROM AUTHOR]

The composition of North American communities is changing due to anthropogenic land-use alteration. Mammalian mesopredators' ability to consume anthropogenic trash due to their generalist diet has been referenced to partially explain their success in altered landscapes as they spread northward. We evaluated this assumption using carbon isotope values (δ13C) of the Virginia opossum (Didelphis virginiana (Kerr, 1792)), a mesopredator expanding its range. δ13C values increase from consumption of C4 plants, including corn, a common food additive in North America. Opossum hairs from the Midwestern U.S. and Northeast were evaluated using generalized linear mixed models (GLMMs) to compare the predictive performances between winter harshness variables and anthropogenic variables. We also evaluated δ13C values through time to test if the temporal pattern of increased corn additives is mirrored in northern opossums. The best-performing GLMM included year and percentage corn fields as positive covariates. Variance in δ13C values increased exclusively in the "cornbelt" Midwest after 1970. δ13C values compared across space and time bolster evidence for the influence of agricultural development on the opossum's range expansion. [ABSTRACT FROM AUTHOR]

Alaria , Didelphodiplostomum and Pharyngostomoides are among genera of diplostomid digeneans known to parasitize mammalian definitive hosts. Despite numerous recent molecular phylogenetic studies of diplostomids, limited DNA sequence data is available from diplostomids parasitic in mammals. Herein, we provide the first 28S rDNA and cox1 mtDNA sequences from morphologically identified, adult specimens of Didelphodiplostomum and Pharyngostomoides. Newly generated 28S sequences were used to infer the phylogenetic interrelationships of these two genera among other major lineages of diplostomoideans. The phylogeny based on 28S and a review of morphology clearly suggests that Pharyngostomoides should be considered a junior synonym of Alaria , while Didelphodiplostomum should be considered a junior synonym of Tylodelphys. Pharyngostomoides procyonis (type species), Pharyngostomoides adenocephala and Pharyngostomoides dasyuri were transferred into Alaria as Alaria procyonis comb. nov. , Alaria adenocephala comb. nov. and Alaria dasyuri comb. nov. ; Didelphodiplostomum variabile (type species) and Didelphodiplostomum nunezae were transferred into Tylodelphys as Tylodelphys variabilis comb. nov. and Tylodelphys nunezae comb. nov. In addition, Alaria ovalis comb. nov. (formerly included in Pharyngostomoides) was restored and transferred into Alaria based on a morphological study of well-fixed, adult specimens and the comparison of cox1 DNA sequences among Alaria spp. The diplostomid genus Parallelorchis was restored based on review of morphology. [ABSTRACT FROM AUTHOR]

The Virginia opossum (Didelphis virginiana), North America's only marsupial, has a range extending from southern Ontario, Canada, to the Yucatan Peninsula, Mexico, and from the Atlantic seaboard to the Pacific. Despite the Virginia opossum's taxonomic uniqueness in relation to other mammals in North America and rapidly expanding distribution, its ecology remains relatively understudied. Our poor understanding of the ecology of this important mesopredator is especially pronounced in the rural southeastern United States. Our goal was to estimate effects of habitat on opossum density within an extensive multi‐year spatial capture‐recapture study. Additionally, we compared the results of this spatial capture‐recapture analysis with a simple relative abundance index. Opossum densities in the relatively underdeveloped regions of the southeastern United States were lower compared to the more human‐dominated landscapes of the Northeast and Midwest. In the southeastern United States, Virginia opossums occurred at a higher density in bottomland swamp and riparian hardwood forest compared to upland pine (Pinus spp.) plantations and isolated wetlands. These results reinforce the notion that the Virginia opossum is commonly associated with land cover types adjacent to permanent water (bottomland swamps, riparian hardwood). The relatively low density of opossums at isolated wetland sites suggests that the large spatial scale of selection demonstrated by opossums gives the species access to preferable cover types within the same landscape. [ABSTRACT FROM AUTHOR]

As urbanization increases, impacts on urban wildlife behavior are becoming more apparent. Using camera traps, we compared activity times of Raccoons (Procyon lotor) with those of Virginia Opossums (Didelphis virginiana) in natural areas of Seattle, Washington. Previous studies found that Virginia Opossums and Raccoons are significantly more active at night than at any other time. However, these studies occurred exclusively in forested or agricultural landscapes. We deployed motion-triggered camera traps in greenspaces of Seattle to test the hypothesis that Raccoons and Virginia Opossums are both primarily active at night in an urban environment. Our results demonstrated a statistically significant difference in activity time distributions between the species. Virginia Opossums were exclusively nocturnal, whereas Raccoons allocated their activity between nocturnal and crepuscular periods. This study provides a snapshot of mesopredator behavior in an environment heavily influenced by humans and informs the effective management of Raccoons in urban areas. [ABSTRACT FROM AUTHOR]

Oral rabies vaccination (ORV) is the primary tool for landscape level control and elimination of rabies virus in terrestrial wildlife species. However, there is currently a limited understanding of how different baiting strategies influence raccoon (Procyon lotor) uptake of ORV baits in non-agricultural habitats in the Southeastern United States, which may hinder the refinement of ORV management for raccoons in this region. Using a combination of new and existing data, we investigated the role of baited area (0.16 vs 3 km2), bait density (75 vs 150 baits/km2) and season (spring vs fall) on placebo ORV bait uptake by raccoons in four rural, non-agricultural habitats in the southeastern United States (bottomland hardwood forest, upland pine forest, riparian forest, and isolated wetlands). Increasing the baited area to 3 km2 increased the proportion of raccoons that consumed baits by 140 % in riparian forests and decreased the proportion consuming baits by 70 % in bottomland hardwood forests. A greater proportion of raccoons consumed baits in riparian habitat in spring compared to fall, but bait density did not influence uptake in either season in this habitat. Increasing the bait density during spring in bottomland hardwoods increased the proportion of raccoons that consumed baits by 270 %, but there was no effect of increasing bait density in bottomland hardwoods during fall. We suggest that variation in habitat contiguity and seasonal resource availability influence how raccoons utilize these habitats which in turn impacts habitat-specific ORV bait uptake. The estimated proportion of raccoons that consumed baits did not exceed 60 % for any treatment, and for most treatments was less than 40 %. These low uptake rates indicate a need for research into additional strategies to maximize raccoon uptake of ORV baits across rural, non-agricultural southeastern landscapes. • Role of oral rabies vaccine (ORV) bait density, area, and season on raccoon uptake varied by habitat. • Variation in bait uptake likely results from differences in how raccoons utilize these habitats. • Raccoons consumed more ORV baits than opossums, but uptake was low overall. [ABSTRACT FROM AUTHOR]