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Anthropogenic activity in coastal areas can damage marine habitats and alter marine mammal behavior and habitat use. Understanding behavioral associations with diverse habitat features in industrialized coastal areas is crucial for marine mammal conservation management. A shore-based digital theodolite was used to assess the behavioral states and habitat use of common bottlenose dolphins (Tursiops truncatus) off Port Aransas, Texas across seasons. The relationship between behavioral states and environmental and geographical variables were analyzed. Behavioral hotspots were identified. Dolphins frequently foraged (46%), indicating the area is an important feeding ground. Dolphins also traveled (25%) and milled (22%), with less frequent occurrences of socializing (6%) and resting (1% of observations). Season, time of day, and distance to shoreline were significant predictors of foraging and traveling behavioral states. Dolphins engaged in all behavioral states closer to seawall shorelines than to mangroves and natural seagrass beds, suggesting that hard shoreline features may influence daily activity patterns. Despite daily anthropogenic operations, bottlenose dolphins use features of the industrialized area (i.e., deeply dredged channels, human-engineered seawalls) to engage in a variety of behaviors. Monitoring of dolphin behavioral states and habitat use in active ship channels are needed to assess changes from baseline data from increasing coastal development and vessel activities. [ABSTRACT FROM AUTHOR]

Bottlenose dolphins (Tursiops truncatus) inhabit waters across a broad natural salinity gradient and exhibit changes in skin condition based on the quality of their environment. Prolonged exposure to low salinities (≤10–20 ppt) degenerates the epidermal barrier and causes cutaneous lesions in dolphins, while the role of high salinity exposure (>35 ppt) in lesion development remains unknown. We assessed seasonal lesion prevalence in three free-ranging dolphin stocks inhabiting coastal Gulf of Mexico (GoM) waters of different salinities (0–30 ppt, 22–35 ppt, and 36+ ppt) using images of dolphin bodies. Lesions were documented on 44% of the dolphins photographed (n = 432), and lesion occurrence was significantly related to cold seasons and water temperatures but not salinity. Cold water temperatures may heighten dolphin susceptibility to infectious pathogens and disease and compound the effects of anthropogenic pollutants in the GoM. As dolphins are a bioindicator species of marine habitat welfare, natural studies assessing dolphin skin may reveal environmental degradation with potential impacts on marine ecosystems and human health. [ABSTRACT FROM AUTHOR]

Simple Summary: Dolphins alter their behavior and movement in response to human coastal activities (e.g., commercial shipping, dredging, ecotourism). The Port of Corpus Christi, Texas, is the largest port in the USA based on total revenue tonnage, yet little research has been conducted on the local bottlenose dolphins since the 1980s, prior to major oil exportation and infrastructure growth. The behavior and movement patterns of dolphins in the presence and absence of vessels were recorded using a shore-based digital theodolite and analyzed using multinomial logistic regression and generalized additive models. Dolphins frequently foraged, traveled, socialized, and milled in the Corpus Christi Ship Channel despite the presence of one or more vessels within 300 m of dolphins during 80% of observations. Dolphin behavior and movement patterns were significantly affected by season, time of day, group composition, and vessel characteristics. Dolphins appear to remain in the active Texas ship channel despite high vessel traffic. The observed dolphin–vessel interactions emphasize the need for long-term monitoring of dolphins near human activities and enforced boating regulations near important marine mammal habitats. Although the Port of Corpus Christi, Texas, has become a top oil exporter, it is unknown if local dolphins are disturbed by high year-round vessel traffic. A shore-based digital theodolite and automatic identification system receiver were used to record data to assess common bottlenose dolphin (Tursiops truncatus) behavioral states and movement patterns in the Corpus Christi Ship Channel (CCSC) in relation to vessel traffic. Multinomial logistic regression and generalized additive models were applied to analyze the data. Vessels were present within 300 m of dolphins during 80% of dolphin observations. Dolphins frequently foraged (40%), traveled (24%), socialized (15%), and milled (14%), but rarely oriented against the current (7%) or rested (1% of observations). Season, time of day, group size, vessel type, vessel size, and number of vessels were significant predictors of dolphin behavioral state. Significant predictors of dolphin movement patterns included season, time of day, group size, calf presence, vessel type, and vessel numbers. The CCSC is an important foraging area for dolphins, yet the high level of industrial activity puts the dolphins at risk of human-related disturbance and injury. There is a crucial need to monitor the impact of increased anthropogenic influences on federally protected dolphins in the active CCSC, with broad application to dolphins in other ports. [ABSTRACT FROM AUTHOR]

Dolphins are often individually identified by unique naturally-acquired markings. Identification becomes difficult when markings heal, or new scars appear. As salt accelerates wound healing in many organisms, the diminishment of scars on common bottlenose dolphins (Tursiops truncatus) residing in varying natural salinities was determined. South Texas contains the only hypersaline lagoon in the USA, located adjacent to hyposaline waters, with genetically distinct populations of dolphins in the two environments. Photographs of dolphin dorsal fins were collected, and scar stability over time was determined and compared by measuring changes in the relative lengths and surfaces of scars. All scars on dolphins in the hypersaline lagoon completely diminished between three to six years, while scars on dolphins in the hyposaline bay ranged in the amount of fading between three to six years. Data from this case study indicate that high salinity may increase the healing speed of wounds on common bottlenose dolphins compared to low salinity, although a larger sample size is needed for robust statistical comparison. Scar diminishment is an important consideration in determining the temporal reliability of photo identification. [ABSTRACT FROM AUTHOR]

Comparisons of 3D shapes have recently been applied to diverse anatomical structures using landmarking techniques. However, discerning evolutionary patterns can be challenging for structures lacking homologous landmarks. We used alpha shape analyses to quantify vaginal shape complexity in 40 marine mammal specimens including cetaceans, pinnipeds, and sirenians. We explored phylogenetic signal and the potential roles of natural and sexual selection on vaginal shape evolution. Complexity scores were consistent with qualitative observations. Cetaceans had a broad range of alpha complexities, while pinnipeds were comparatively simple and sirenians were complex. Intraspecific variation was found. Three‐dimensional surface heat maps revealed that shape complexity was driven by invaginations and protrusions of the vaginal wall. Phylogenetic signal was weak and metrics of natural selection (relative neonate size) and sexual selection (relative testes size, sexual size dimorphism, and penis morphology) did not explain vaginal complexity patterns. Additional metrics, such as penile shape complexity, may yield interesting insights into marine mammal genital coevolution. We advocate for the use of alpha shapes to discern patterns of evolution that would otherwise not be possible in 3D anatomical structures lacking homologous landmarks. [ABSTRACT FROM AUTHOR]

Few studies have explored the mating patterns of free‐ranging cetaceans, largely because of logistical challenges. We used an unmanned aerial vehicle (UAV) to follow and video‐record 25 groups of mating dusky dolphins (Lagenorhynchus obscurus) near the surface of the water and examine how behavior patterns varied with mating group type. We collected aerial footage of dolphins mating in traditional Isolated Pods and within Integrated Pods and compared differences in the number of mating animals, swimming speed, bearing change, percent time at the surface of the water, female respiration rate, copulatory position rate, and sex‐specific mating behaviors. Only the mean number of mating animals and some sex‐specific mating behaviors varied significantly between the two mating group types. More dolphins were engaged in mating behaviors in Isolated Pods than Integrated Pods. Males engaged in more interference behaviors in Isolated Pods compared to Integrated Pods. Females performed fewer speed bursts but more rolls on their backs in Integrated Pods compared to Isolated Pods. Several similarities and differences were found in comparison to boat‐based research of the same population of dolphins. We highlight the value of UAVs for noninvasive and accurate collection of cetacean behavioral data. [ABSTRACT FROM AUTHOR]

In species with limited opportunities for pre‐ejaculatory sexual selection (behavioural components), post‐ejaculatory mechanisms may provide opportunities for mate choice after gametes have been released. Recent evidence from a range of taxa has revealed that cryptic female choice (i.e., female‐mediated differential fertilization bias), through chemical cues released with or from eggs, can differentially regulate the swimming characteristics of sperm from various males and ultimately determine male fertilization success under sperm competition. We assessed the potential role that such female‐modulated chemical cues play in influencing sperm swimming characteristics in beach‐spawning capelin (Mallotus villosus), an externally fertilizing fish that mates as couples (one male and one female) or threesomes (two males and one female) with presumably limited opportunities for pre‐ejaculatory sexual selection. We assayed sperm swimming characteristics under varying doses and donor origins of egg cues and also examined the possibility of assortative mating based on body size. We found mating groups were not associated by size, larger males did not produce better quality ejaculates, and egg cues (regardless of dosage or donor identity) did not influence sperm swimming characteristics. Our findings suggest that intersexual pre‐ejaculatory sexual selection and cryptic female choice mediated by female chemical cues are poorly developed in capelin, possibly due to unique natural selection constraints on reproduction. [ABSTRACT FROM AUTHOR]

We evaluated whether morphological traits in capelin, Mallotus villosus, that appear to be sexually selected (pectoral fin, pelvic fin, anal fin, lateral ridge) were larger and more variable in males than females compared with naturally selected morphological traits (eyes, dorsal fin). Photographs were obtained of 136 capelin captured at two spawning sites and standardised measurements were taken of six morphological traits. Males had larger traits than females for a given body size and this was most pronounced in the traits thought to be sexually selected. Body size explained much of the variation in female traits but less variation in male traits, suggesting alternative selection pressures are involved. We suggest that larger male body size aids in endurance rivalry and sexually dimorphic traits help males to remain in physical contact with females while spawning on the beach. [ABSTRACT FROM AUTHOR]

Sexual selection influences both genital diversity and mating behaviors, yet the integrated coevolution of pre- (behavioral) and postcopulatory (anatomical) traits in both sexes has received little attention. Traits could potentially evolve through an arms race model of escalations in male persistence and female resistance, and/or through a tradeoff model of inverse correlations between investments in pre- and postcopulatory traits. Preand postcopulatory traits of dusky dolphins (Lagenorhynchus obscurus) were compared with bottlenose dolphins (Tursiops spp.) and harbor porpoises (Phocoena phocoena). Relative testes size and vaginal complexity were measured from dissected specimens. Behavioral traits were analyzed from video recordings of individuals in free-ranging populations. Female precopulatory and male postcopulatory traits were associated, whereas female and male postcopulatory traits or female pre- and postcopulatory traits were not associated. Dusky dolphins differed substantially in several behavioral traits including longer durations of mating group interactions, lower rates of copulation attempts, more males per group, and higher female behavioral resistance. To explore complex processes of integrative coevolution, we recommend future research incorporate pre- and postcopulatory traits and focus on alternative measures of female resistance and male persistence. [ABSTRACT FROM AUTHOR]

The challenges of monitoring fully aquatic and long-living mammals have limited research on cetaceans that spans several decades to only a few populations. We report the first long-term assessment of association and residency patterns of dusky dolphins (Lagenorhynchus obscurus) off Kaikoura, New Zealand. Dorsal fin images, spanning 30 years of data collection, were used for photo-identification and social structure analyses. A total of 4,022 uniquely marked individuals were identified. Most (80%) were sighted only one time. The population of dusky dolphins off Kaikoura appears to be open, with the possibility of immigration and emigration. Dusky dolphins showed preferences for assembly into either large or small groups, which appear to drive association patterns. They did not demonstrate significant preferred or avoided associations with each other, and had overall weak association patterns. Individuals reside in the Kaikoura area for approximately eight years, and also have temporallv stable associations lasting approximately eight years. Dusky dolphins fit the model of a fission-fusion societv, and their association patterns may reflect unique local ecological conditions and foraging opportunities. [ABSTRACT FROM AUTHOR]

Complex foldings of the vaginal wall are unique to some cetaceans and artiodactyls and are of unknown function(s). The patterns of vaginal length and cumulative vaginal fold length were assessed in relation to body length and to each other in a phylogenetic context to derive insights into functionality. The reproductive tracts of 59 female cetaceans (20 species, 6 families) were dissected. Phylogenetically-controlled reduced major axis regressions were used to establish a scaling trend for the female genitalia of cetaceans. An unparalleled level of vaginal diversity within a mammalian order was found. Vaginal folds varied in number and size across species, and vaginal fold length was positively allometric with body length. Vaginal length was not a significant predictor of vaginal fold length. Functional hypotheses regarding the role of vaginal folds and the potential selection pressures that could lead to evolution of these structures are discussed. Vaginal folds may present physical barriers, which obscure the pathway of seawater and/or sperm travelling through the vagina. This study contributes broad insights to the evolution of reproductive morphology and aquatic adaptations and lays the foundation for future functional morphology analyses. [ABSTRACT FROM AUTHOR]

In fission-fusion social systems with scramble competition between males, multiple males join mating groups while surrounding an oestrous female. If male decisions to join a mating group have been shaped by natural selection, then there should be an optimal group size resulting from the trade-offs between the benefits of monopolizing a female in small groups and the energy lost in defending her from rivals in large groups. Male dusky dolphins ( Lagenorhynchus obscurus) off Kaikoura, New Zealand, provide a unique opportunity to assess the optimum mating group size because they join transient mating groups not confounded by foraging or predator evasion. Within aggregations of up to 1000 individuals, males search for oestrous females, encountering choices of staying with a large mating group or leaving to find a smaller group. Mating groups typically involve multiple males mating with a single female. We conducted focal follows of mating groups (N = 44) by vessel from November 2011 through January 2012. We used video and a GPS to record group size, behaviour and movement. For each group, we measured potential costs ( Swim Speed, Loss of Monopolization Potential) and benefits ( Copulation Rate and Duration, Energy Savings). Only Loss of Monopolization Potential was positively correlated with group size, while Energy Savings was negatively correlated. Using these two factors as utility functions, we constructed an optimality model and predicted the optimal mating group size to be seven individuals with a range of 4-11 individuals due to variance. The observed modal mating group size was five dolphins, with a range of 2-15. We compare variation in mating group currencies and sizes to past studies. We discuss potential limitations of applying optimality models to predict mating group size for socially complex and behaviourally plastic species such as dolphins. [ABSTRACT FROM AUTHOR]

Between October 2011 and December 2013, three interactions between dusky dolphins (Lagenorhynchus obscurus) and common New Zealand octopuses (Pinnoctopus cordiformis) were witnessed and photographed off Kaikoura, New Zealand. In two interactions, an octopus was attached to a dusky dolphin; and in a third interaction, dusky dolphins appeared to be playing with an octopus. The attachment might have been an escape tactic for the octopuses. This is the first published record of interactions between dusky dolphins and octopuses in New Zealand. The few anecdotal reports of octopuses attached to dolphins are limited to species that commonly prey on octopuses. The evidence for dusky dolphins foraging on octopuses off Kaikoura is weak. The two species have different habitats but could come into initial contact through shallow nearshore dives performed by the dusky dolphins or by other species observed in the area, including New Zealand fur seals (Arctocephalus forsteri), humpback whales (Megaptera novaeangliae), or fishermen retrieving craypots. When the dusky dolphins encountered this unusual object in their environment, they may have initiated exploratory or playful behavior, which changed to distressed or defensive behavior upon the attachment of the octopuses. The erratic behaviors of the dolphins, including tail thrashes, rolling over, and rapid changes in swimming speed and direction, indicate they were disturbed by the presence of the affixed octopus. The dolphins did not perform acrobatic leaps, which are predicted to remove or reposition large "hitchhikers." [ABSTRACT FROM AUTHOR]

Few studies have investigated the origins of distinctive marks on cetaceans and quantitatively evaluated the causal factors. We used photo-identification data to categorize the ecological sources of scars and notches on the dorsal fins of freeranging dusky dolphins (Lagenorhynchus obscurus) off Kaikoura, New Zealand. Dorsal fin photographs of 1,171 individuals that had marks from ecological sources were collected from October 2011 through January 2012. Photographs of scars and notches were compared to marks of known origin, cross-validated by experts, and categorized as derived from conspecifics, killer whales, sharks, vessel strikes, fishing gear, or unknown. A total of 1,019 dusky dolphins had notches, of which 419 (41%) individuals had additional scars. A smaller subset of dolphins (152 individuals) had only scars or pigmentations as marks. The marks on the majority of dusky dolphins were attributed to intraspecific interactions (notches: 84%, n = 983; scars: 30%, n = 355). Indications of predation attempts (sharks: 0.17%, n = 2; killer whales: 0.09%, n = 1; unclassified natural predators: 0.26%, n = 3) and human impact (net/line: 0.43%, n = 4; vessel: 0.17, n = 2; unclassified human impact: 0.34%, n = 4) were comparatively low. These results are consistent with previous studies and indicate that most marks on dusky dolphins are caused by conspecifics and that predation pressure and bycatch rates are low off Kaikoura. We suggest that these data indicate that current management actions regulating commercial and recreational boating activities in the area are sufficient, with no need for immediate modification. [ABSTRACT FROM AUTHOR]

Background: Free-flying insectivorous bats occasionally collide with stationary objects they should easily detect by echolocation and avoid. Collisions often occur with lighted objects, suggesting ambient light may deleteriously affect obstacle avoidance capabilities. We tested the hypothesis that free-flying bats may orient by vision when they collide with some obstacles. We additionally tested whether acoustic distractions, such as "distress calls" of other bats, contributed to probabilities of collision. Methodology/Principal Findings: To investigate the role of visual cues in the collisions of free-flying little brown bats (Myotis lucifugus) with stationary objects, we set up obstacles in an area of high bat traffic during swarming. We used combinations of light intensities and visually dissimilar obstacles to verify that bats orient by vision. In early August, bats collided more often in the light than the dark, and probabilities of collision varied with the visibility of obstacles. However, the probabilities of collisions altered in mid to late August, coincident with the start of behavioural, hormonal, and physiological changes occurring during swarming and mating. Distress calls did not distract bats and increase the incidence of collisions. Conclusions/Significance: Our findings indicate that visual cues are more important for free-flying bats than previously recognized, suggesting integration of multi-sensory modalities during orientation. Furthermore, our study highlights differences between responses of captive and wild bats, indicating a need for more field experiments. [ABSTRACT FROM AUTHOR]

Background: In the wild, frugivorous and nectarivorous bats often eat fermenting fruits and nectar, and thus may consume levels of ethanol that could induce inebriation. To understand if consumption of ethanol by bats alters their access to food and general survival requires examination of behavioural responses to its ingestion, as well as assessment of interspecific variation in those responses. We predicted that bats fed ethanol would show impaired flight and echolocation behaviour compared to bats fed control sugar water, and that there would be behavioural differences among species. Methodology/Principal Findings: We fed wild caught Artibeus jamaicensis, A. lituratus, A. phaeotis, Carollia sowelli, Glossophaga soricina, and Sturnira lilium (Chiroptera, Phyllostomidae) sugar water (44 g of table sugar in 500 ml of water) or sugar water with ethanol before challenging them to fly through an obstacle course while we simultaneously recorded their echolocation calls. We used bat saliva, a non-invasive proxy, to measure blood ethanol concentrations ranging from 0 to >0.3% immediately before flight trials. Flight performance and echolocation behaviour were not significantly affected by consumption of ethanol, but species differed in their blood alcohol concentrations after consuming it. Conclusions/Significance: The bats we studied display a tolerance for ethanol that could have ramifications for the adaptive radiation of frugivorous and nectarivorous bats by allowing them to use ephemeral food resources over a wide span of time. By sampling across phyllostomid genera, we show that patterns of apparent ethanol tolerance in New World bats are broad, and thus may have been an important early step in the evolution of frugivory and nectarivory in these animals. [ABSTRACT FROM AUTHOR]

The article reports on the observation of mother and calve behavior among dusky dolphins via the use of an unmanned aerial vehicle (UAV). Particular attention was given to swimming speed, inter-adult distance, and respiration and suckling rates in the area between the Kaikoura Peninsula and the Haumuri Bluffs, New Zealand.

The article describes the first documented observation of placental expulsion by a long-finned pilot whale, which was captured on video by an unmanned aerial system (UAS) in coastal waters of the Shetland Isles, Scotland, United Kingdom. Topics include examines the advent and development of UAS technology provides novel opportunities to observe and document biologically significant events that are challenging to observe via boat or from land.

The Golden Gate Bridge in San Francisco Bay provides a non-invasive aerial platform where harbor porpoises (Phocoena phocoena) can be observed mating. We photographed 144 mating events over an eight-year period (2010 to 2018) occurring in all seasons. The mating habits of free-ranging male harbor porpoises are systematically described, a first for any member of the family Phocoenidae. The males' rapid sexual approaches toward females were characterized by high energy and precision timing as males rushed to contact females surfacing to breathe. Males always attempted to copulate by positioning their ventral sides on the females' left side. This extreme laterality in sexual approach has not been reported for any cetacean. Males approached females with force and speed that often resulted in male aerial behaviors (69% of mating attempts). These behaviors, observed exclusively in mating contexts, included leaps and splashes that counter the species' reputation for inconspicuous behavior. Males also displayed their ventrum or penis toward females without attempting to copulate. The penis was visible in 60% of the 96 mating events for which the ventrum could be observed. with intromission confirmed in one event. Males always initiated mating and approached lone females m 62Scc of mating events. Calves accompanied females during 25% of mating events. Calves were temporarily separated from their mothers by the approaching males in approximately half of these events. Additional adults were observed in 12.5°c of groups, although no male-male interactions were observed. Our findings on the unique mating pattern exhibited by male harbor porpoises validate some predictions made about their behavior based on their reproductive biology and anatomy. The data support the hypothesis that males compete primarily by sperm competition and not contest competition. [ABSTRACT FROM AUTHOR]

Bottlenose dolphins ( Tursiops truncatus ) inhabit environments with variable natural salinities and experience physiological imbalances from extreme salinity fluctuations. Low salinity exposure (≤10) disrupts osmoregulation and increases the production of steroid hormones aldosterone (electrolyte balance) and cortisol (stress response). The effect(s) of high salinity exposure (>35) on steroid hormone production in bottlenose dolphins has not previously been assessed. We measured stress hormones (aldosterone, corticosterone, cortisol, and cortisone) and reproductive hormones (progesterone and testosterone) in three stocks of free-ranging bottlenose dolphins inhabiting different natural salinities across the Gulf of Mexico (0-30, 22-35, 36+). Hormones were extracted from the blubber of 82 remotely biopsied dolphins and quantified using ultraperformance liquid chromatography coupled with Orbitrap Fusion mass spectrometry. A positive correlation was found between cortisol (10.38 ± 0.8 ng/g, n = 13) and salinity ( r = 0.62). Aldosterone (58.9 ± 17.2 ng/g, n = 5) was quantified in dolphin blubber for the first time and was detected across the salinity gradient but was not significantly related to salinity levels. Concentrations of testosterone were seasonally variable. This study enhances our understanding of how climate changes and extensive anthropogenic stressors challenge homeostasis in a marine bioindicator species., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

For 88 years, biologists and engineers have sought to understand the hydrodynamics enabling dolphins to swim at speeds seemingly beyond their energetic capabilities, a phenomenon known as Gray's paradox. Hydromechanical models calculating the drag of swimming dolphins estimated power requirements for sustained high-speed swimming, which were physiologically impossible. Using an uncrewed aerial vehicle, we calculated the total power of free-ranging dusky dolphins ( Lagenorhynchus obscurus ) at speeds from 0.9 to 6.9 m s -1 , deriving drag coefficients ( Cd ) and drag. Our results showed that the Cd decreased exponentially with speed, reducing drag by up to 89% at speeds >2 m s -1 , with an additional 17% reduction during porpoising (>4.0 m s -1 ). At 6.9 m s -1 , drag was 32 N, with a power of 15.8 W kg -1 , nearly identical to the mass-specific allometric prediction for the maximum aerobic capacity of other mammals and physiologically possible. The Cd at speeds >2.5 m s -1 indicated reduced turbulence in the boundary layer around the dolphin's body, thereby reducing drag. The ability of dusky dolphins to swim at sustained high speeds resulted from an exponential decrease in Cd , which was further reduced by porpoising, thereby explaining the low drag and locomotory power that resolved Gray's paradox.

Cetaceans exhibit vaginal folds, unusual protrusions of the vaginal wall into the vaginal lumen. Inconsistent terminology and a lack of anatomical landmarks in the literature have hindered comparative studies of the form and function of vaginal folds. Our objectives are to: (1) develop a standardized measurement protocol for the reproductive tracts of female cetaceans, (2) assess variation in morphometrics within the common bottlenose dolphin (Tursiops truncatus), and (3) determine if vaginal muscle is skeletal, and therefore of somatic origin in this species. We selected 15 measurements to characterize female reproductive tracts and evaluated variability using fresh or frozen-thawed specimens from southeastern USA representing a range of sexual maturity states and reproductive states (n = 18 specimens). Presence of skeletal muscle and variation in the density of muscle banding were assessed using 90 histological samples (n = 5 specimens). Analyses of the gross morphological data revealed that the dolphins generally had one large vaginal fold that bisected the vaginal lumen. Vaginal morphology was similar for sexually mature and immature specimens and across reproductive states. The histological data revealed that the vaginal musculature consisted of smooth muscle, consistent with other mammals, leading us to conclude that vaginal contractions are likely under autonomic rather than somatic control. No differences were found in the density of smooth muscle banding among vaginal regions or sexual maturity states. Our systematic protocol lays the foundation for evaluating the function (e.g., sexual selection, natural selection) and evolution of vaginal folds., (© 2016 Wiley Periodicals, Inc.)