Juvenile Alligator Research Articles

Golf course living leads to a diet shift for American alligators.

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.

Big Turtles Start Small: Trapping Juvenile Alligator Snapping Turtles in South Mississippi and Implications for Conservation

Macrochelys (alligator snapping turtles), the largest freshwater turtles in North America, were recently proposed for threatened status under the US Endangered Species Act. Many previous surveys have focused on catching these large turtles in large river systems, but few surveys have focused on targeting hatchlings and juveniles, particularly in smaller rivers and creeks. I trapped extensively within the Pascagoula River drainage using small, baited crayfish traps, and a considerable focus of the study was in small rivers and streams. Juvenile Macrochelys temminckii (Alligator Snapping Turtle; 42.2–192 mm) were detected in small streams and large rivers (30.4 km2–22,000 km2), and the small traps were effective at capturing young alligator snapping turtles. Smaller streams are logistically harder to trap from a boat, but small streams should not be overlooked when sampling for this species, as these streams may have served as refugia during commercial harvest over the past century.

About the Cover

Next article FreeAbout the CoverPDFPDF PLUSFull Text Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinked InRedditEmailQR Code SectionsMoreThe cover image features a hatchling American alligator (Alligator mississippiensis) emerging from its nest. Like many non-mammalian vertebrates, the temperature that alligators experience during development determines their sex. Temperature-dependent sex determination (TSD) is a form of developmental plasticity that may provide insight into how taxa respond to fluctuating environments and extreme conditions that are predicted to intensify with ongoing climate change. However, the evolutionary drivers of TSD are unresolved for many species, including crocodilians. In this issue, S. L. Bock, M. D. Hale, T. R. Rainwater, P. M. Wilkinson, and B. B. Parrott (pp. 43–54) demonstrate that fluctuating versus constant temperature conditions have different effects on the juvenile phenotype of alligators, and that warmer temperatures produce males with greater residual yolk reserves and larger hatchling sizes. Variation in developmental costs at different incubation temperatures may therefore contribute to the evolution of TSD.Coastal ecosystems are naturally variable in important physical stressors like temperature, salinity, pH, and hypoxia. Understanding how species adapt to such fluctuating conditions should enable better predictions of the evolutionary responses of coastal communities to climate change. In their Introduction (pp. 1–3), the editors of the series—Patrick J. Krug, John P. Wares, and Jonathan D. Allen—argue for a broader study of plasticity and local adaptation in aquatic organisms in the context of a fast-changing climate. This symposium issue brings together contributions examining all life stages of freshwater, estuarine, and marine organisms and uses approaches ranging from genomic to experimental techniques to understand survival strategies in unpredictable versus stable environments.Credits: Photo of juvenile alligator, Benjamin B. Parrott, Odum School of Ecology, University of Georgia. Cover design, Matt Lang, University of Chicago Press. Next article DetailsFiguresReferencesCited by The Biological Bulletin Volume 241, Number 1August 2021Adaptive and Plastic Responses to Environmental Variation Published in association with the Marine Biological Laboratory Article DOIhttps://doi.org/10.1086/717022 Views: 304 © 2021 by The University of Chicago. All rights reserved.PDF download Crossref reports no articles citing this article.

Scaling of axial muscle architecture in juvenile Alligator mississippiensis reveals an enhanced performance capacity of accessory breathing mechanisms.

Quantitative functional anatomy of amniote thoracic and abdominal regions is crucial to understanding constraints on and adaptations for facilitating simultaneous breathing and locomotion. Crocodilians have diverse locomotor modes and variable breathing mechanics facilitated by basal and derived (accessory) muscles. However, the inherent flexibility of these systems is not well studied, and the functional specialisation of the crocodilian trunk is yet to be investigated. Increases in body size and trunk stiffness would be expected to cause a disproportionate increase in muscle force demands and therefore constrain the basal costal aspiration mechanism, necessitating changes in respiratory mechanics. Here, we describe the anatomy of the trunk muscles, their properties that determine muscle performance (mass, length and physiological cross‐sectional area [PCSA]) and investigate their scaling in juvenile Alligator mississippiensis spanning an order of magnitude in body mass (359 g–5.5 kg). Comparatively, the expiratory muscles (transversus abdominis, rectus abdominis, iliocostalis), which compress the trunk, have greater relative PCSA being specialised for greater force‐generating capacity, while the inspiratory muscles (diaphragmaticus, truncocaudalis ischiotruncus, ischiopubis), which create negative internal pressure, have greater relative fascicle lengths, being adapted for greater working range and contraction velocity. Fascicle lengths of the accessory diaphragmaticus scaled with positive allometry in the alligators examined, enhancing contractile capacity, in line with this muscle's ability to modulate both tidal volume and breathing frequency in response to energetic demand during terrestrial locomotion. The iliocostalis, an accessory expiratory muscle, also demonstrated positive allometry in fascicle lengths and mass. All accessory muscles of the infrapubic abdominal wall demonstrated positive allometry in PCSA, which would enhance their force‐generating capacity. Conversely, the basal tetrapod expiratory pump (transversus abdominis) scaled isometrically, which may indicate a decreased reliance on this muscle with ontogeny. Collectively, these findings would support existing anecdotal evidence that crocodilians shift their breathing mechanics as they increase in size. Furthermore, the functional specialisation of the diaphragmaticus and compliance of the body wall in the lumbar region against which it works may contribute to low‐cost breathing in crocodilians.

Anatomical and histological analyses reveal that tail repair is coupled with regrowth in wild-caught, juvenile American alligators (Alligator mississippiensis)

Reptiles are the only amniotes that maintain the capacity to regenerate appendages. This study presents the first anatomical and histological evidence of tail repair with regrowth in an archosaur, the American alligator. The regrown alligator tails constituted approximately 6–18% of the total body length and were morphologically distinct from original tail segments. Gross dissection, radiographs, and magnetic resonance imaging revealed that caudal vertebrae were replaced by a ventrally-positioned, unsegmented endoskeleton. This contrasts with lepidosaurs, where the regenerated tail is radially organized around a central endoskeleton. Furthermore, the regrown alligator tail lacked skeletal muscle and instead consisted of fibrous connective tissue composed of type I and type III collagen fibers. The overproduction of connective tissue shares features with mammalian wound healing or fibrosis. The lack of skeletal muscle contrasts with lizards, but shares similarities with regenerated tails in the tuatara and regenerated limbs in Xenopus adult frogs, which have a cartilaginous endoskeleton surrounded by connective tissue, but lack skeletal muscle. Overall, this study of wild-caught, juvenile American alligator tails identifies a distinct pattern of wound repair in mammals while exhibiting features in common with regeneration in lepidosaurs and amphibia.

Evolutionary and ontogenetic changes of the anatomical organization and modularity in the skull of archosaurs

Comparative anatomy studies of the skull of archosaurs provide insights on the mechanisms of evolution for the morphologically and functionally diverse species of crocodiles and birds. One of the key attributes of skull evolution is the anatomical changes associated with the physical arrangement of cranial bones. Here, we compare the changes in anatomical organization and modularity of the skull of extinct and extant archosaurs using an Anatomical Network Analysis approach. We show that the number of bones, their topological arrangement, and modular organization can discriminate birds from non-avian dinosaurs, and crurotarsans. We could also discriminate extant taxa from extinct species when adult birds were included. By comparing within the same framework, juveniles and adults for crown birds and alligator (Alligator mississippiensis), we find that adult and juvenile alligator skulls are topologically similar, whereas juvenile bird skulls have a morphological complexity and anisomerism more similar to those of non-avian dinosaurs and crurotarsans than of their own adult forms. Clade-specific ontogenetic differences in skull organization, such as extensive postnatal fusion of cranial bones in crown birds, can explain this pattern. The fact that juvenile and adult skulls in birds do share a similar anatomical integration suggests the presence of a specific constraint to their ontogenetic growth.

A Trapping Survey Targeting Head-Started Alligator Snapping Turtles in Southwest Louisiana

AbstractThe alligator snapping turtle Macrochelys temminckii is the largest freshwater turtle in North America and humans seek it as a food source, primarily in Louisiana. Scientists point to decades of intensive commercial harvest of alligator snapping turtles as a cause of population declines. The Louisiana Department of Wildlife and Fisheries initiated a head-start program for alligator snapping turtles and released 53 head-started juveniles at seven sites along an approximately 5.7-km stretch of Bundick Creek in southwest Louisiana between November 2015 and October 2016. Before release, department personnel measured, weighed, and marked all alligator snapping turtles with both an internal passive integrated transponder tag and a numbered external tag. In 2018, the U.S. Geological Survey initiated a turtle trapping survey at those seven release sites targeting the head-started alligator snapping turtles. In 1 wk of trapping effort at each site, we recorded 69 turtle captures comprising seven species, including 15 alligator snapping turtles (representing 12 individuals). Of those 12 individuals, 8 were head-started juveniles and 4 were native to the creek. A landowner captured an additional head-started juvenile alligator snapping turtle during our trapping and we took measurements before its release. A minimum of 17% of head-started alligator snapping turtles survived since release, and we trapped most captured head-started individuals near their release site; the captured individuals exhibited growth consistent with other studies, indicating acclimatization to their new environment. Three head-started alligator snapping turtles had their external tags entangled in the net mesh, and two of these turtles drowned. An additional two head-started individuals lost their external tags in the natural environment prior to their capture in this study. The Louisiana Department of Wildlife and Fisheries discontinued the use of external tags based on our findings, as these tags were detrimental to the health of head-started turtles.

Hydrologic Correlates of Reproductive Success in the Alligator Gar

AbstractPrevious work relating adult age data to historic hydrology indicated that strong year‐classes of Alligator Gar Atractosteus spatula were rare, tied to major flooding events, and linked to the inundation and connectivity of floodplain habitats. Although spawning habitat suitability criteria have been correlated with successful recruitment in Texas Alligator Gar populations, direct evaluation of recruitment documenting young‐of‐the‐year (age‐0) presence or abundance has not been reported. To specify conditions associated with successful spawning and recruitment of Alligator Gar, we sampled for age‐0 fish monthly from May to July 2013–2017 in the Trinity River and from May to July 2015–2017 in Choke Canyon Reservoir. Suitability criteria predicted strong year‐classes in 2015 and 2016 for the Trinity River and in 2015 for Choke Canyon Reservoir; the predictions were confirmed by the presence of abundant age‐0 Alligator Gar in those systems and years. Hatch dates of juvenile Alligator Gar were estimated from otoliths and compared to corresponding environmental and hydrologic conditions. Hatch date analyses indicated a protracted spawning duration in 2015 associated with extended widespread flooding and a narrower range of spawning dates in 2016. Due to rapid growth and variable gear efficacy relative to fish size, multiple gears were required to assess the full size range of age‐0 Alligator Gar. A standardized sampling framework that included visual searching and floating mini‐fyke nets effectively sampled age‐0 Alligator Gar from 15 to 650 mm TL. We recommend a two‐tiered approach for predicting and monitoring Alligator Gar recruitment. First, the monitoring of hydrology and the application of suitability criteria can provide an early predictor of potential Alligator Gar reproductive success. If conditions are favorable for spawning, then sampling for age‐0 Alligator Gar can confirm recruitment and can give an indication of the spatial extent (visual searching) and relative abundance (visual searching and/or mini‐fyke nets) of successful reproduction.

Marking Otoliths of Alligator Gar by Immersion in Oxytetracycline

AbstractAlligator Gar Atractosteus spatula are increasingly being stocked to restore populations, making the need to identify stocked individuals important for monitoring. Oxytetracycline (OTC) immersion allows for large numbers of fish to be marked simultaneously, thus eliminating the need to handle fish individually, but protocols for doing so have not been investigated fully for this species. In this study, we sought to identify dosages of OTC (concentration and duration of exposure) that would successfully mark juvenile Alligator Gar while minimizing mortality as a result of the marking procedures. Juvenile Alligator Gar (38 ± 4.4 mm [mean ± SE]) were collected from raceways at Tishomingo National Fish Hatchery 18–22 d after hatch and were marked during transport to the Oklahoma Fishery Research Laboratory. Ten individuals per treatment (360 total individuals) were randomly placed into one of three replicates containing one of four concentration × duration combinations of Pennox 343 OTC solution. Juvenile Alligator Gar were exposed to an OTC concentration of 0 (control), 500, 600, or 700 mg/L for a duration of 4, 5, or 6 h. Asteriscus, lapillus, and sagittal otoliths were examined for mark presence at 14 d postexposure by using fluorescent microscopy. The OTC concentration and duration both affected mean mark quality similarly among otolith types. Mortality increased with increasing OTC concentration, suggesting that a balance between concentration and duration is needed to achieve marking goals. Based on our findings, batch marking of Alligator Gar was successful at OTC concentrations from 500 to 700 mg/L for 4–6 h, although immersion at 500 mg/L for 6 h and 600 mg/L for 4–6 h produced the best balance between high mark quality and low associated mortality.

Validation of Annuli and Identification of Discontinuities in Sagittal Otoliths of Juvenile Alligator Gar

AbstractAnnual increment periodicity has been validated in sagittal otoliths of Alligator Gar Atractosteus spatula; however, discontinuities (often referred to as false annuli or checks) are common in early years, potentially affecting both accuracy and precision. We used up to four injections of oxytetracycline (OTC) to induce time stamps associated with annuli (opaque zones) in the otoliths of juvenile Alligator Gar (ages 2–6; n = 68). These OTC marks allowed us to test a reader's ability to distinguish discontinuities (hereafter, “checks”) from annuli by using established criteria. In addition, the OTC marks were used to infer the timing of translucent zone and opaque zone formation. Although the reader's error rate was low (6%), some checks were essentially indistinguishable from annuli. Checks were common, occurring in over half of the otoliths examined and within all annual increments in these juvenile fish. The association of all OTC marks with the opaque zones of the annual increment further validates annulus formation in juvenile Alligator Gar and indicates that these narrow zones formed approximately between November and June. Subsequently, it can be inferred that the much wider translucent zones formed from about June to November. Although opaque zone formation was complete by June, new annuli were not distinguishable from the ventral edge of the otolith until translucent material was deposited beyond the annuli. In our samples, only 22.2% of the otoliths from fish sacrificed on June 30 (n = 9) had fully visible annuli along the edge of the otolith. Based on multiple studies, it is apparent that annual increments form in the sagittal otoliths of Alligator Gar throughout their lives; however, the interpretation of these increments can be very difficult. In our experience, the OTC marking of fish can provide a valuable tool for training and verification programs needed for this species and for other long‐lived fishes that pose difficulties in age estimation.

Ontogenetic shifts in prey selection and foraging behaviour of larval and early juvenile alligator gar (Atractosteus spatula)

AbstractThe early foraging ecology of alligator gar (Atractosteus spatula) is poorly documented, with little information available on young‐of‐year food habits or ontogenetic diet shifts. We conducted laboratory experiments to quantify prey selection and foraging behaviours of larval and early juvenile alligator gar (16–80 mm TL) simultaneously offered zooplankton, chironomid larvae and one of three densities of fish prey. The smallest size groups of alligator gar consumed zooplankton almost exclusively, but with increasing size, selection for zooplankton declined and selection for fish prey increased. At higher densities of fish prey, alligator gar exhibited lower selection for zooplankton and positively selected for fish at smaller sizes. Ingestion efficiencies for chironomids were considerably lower than for zooplankton or fish prey, resulting in low rates of consumption and negative selection for chironomids by all size groups of alligator gar. Fish prey elicited a different foraging response from alligator gar than zooplankton or chironomids, as alligator gar pursued and struck at fish over longer distances than for other prey types. With increasing size, alligator gar used a wider vertical range of the water column for foraging, changed their strike tactics and exhibited decreased handling times for zooplankton and fish. These observations indicate that alligator gar undergo several functional and behavioural changes during early ontogeny that facilitate a rapid transition to piscivory, but fish prey density strongly affects prey consumption patterns and the size at which alligator gar transition to piscivory.

The Molecular Circuit Regulating Tooth Development in Crocodilians

Alligators have robust regenerative potential for tooth renewal. In contrast, extant mammals can either renew their teeth once (diphyodont dentition, as found in humans) or not at all (monophyodont dentition, present in mice). Previously, the authors used multiple mitotic labeling to map putative stem cells in alligator dental laminae, which contain quiescent odontogenic progenitors. The authors demonstrated that alligator tooth cycle initiation is related to β-catenin/Wnt pathway activity in the dental lamina bulge. However, the molecular circuitry underlying the developmental progression of polyphyodont teeth remains elusive. Here, the authors used transcriptomic analyses to examine the additional molecular pathways related to the process of alligator tooth development. The authors collected juvenile alligator dental laminae at different developmental stages and performed RNA-seq. This data shows that Wnt, bone morphogenetic protein (BMP), and fibroblast growth factor (FGF) pathways are activated at the transition from pre-initiation stage (bud) to initiation stage (cap). Intriguingly, the activation of Wnt ligands, receptors and co-activators accompanies the inactivation of Wnt antagonists. In addition, the authors identified the molecular circuitry at different stages of tooth development. The authors conclude that multiple pathways are associated with specific stages of tooth development in the alligator. This data shows that Wnt pathway activation may play the most important role in the initiation of tooth development. This result may offer insight into ways to modulate the genetic controls involved in mammalian tooth renewal.

How Doth the Little Crocodilian: Analyzing the Influence of Environmental Viscosity on Feeding Performance of Juvenile Alligator mississippiensis.

Wetland habitats are used as nursery sites for hatchling and juvenile alligators (Alligator mississippiensis), where they utilize prey from aquatic and terrestrial settings. However, little is known about how viscosity of the medium influences feeding performance. We hypothesized that timing and linear excursion feeding kinematic variables would be different for individuals feeding on prey above the water compared with the same individuals feeding underwater. Individuals were fed immobile fish prey and feeding events were recorded using a high speed video camera. Feeding performance was summarized by analyzing three feeding kinematic variables (maximum gape, maximum gape velocity, duration of feeding bout) and success of strike. Results of a series of paired t-tests indicated no significant difference in kinematic variables between feeding events above water compared with underwater. Similarity in feeding performance could indicate that prey-capture is not altered by environmental viscosity or that feeding behavior can mitigate its influence. Behavioral differences were observed during feeding events with alligators approaching underwater prey having their mouths partially opened versus fully closed when feeding above water. This behavior could be an indication of a strategy used to overcome water viscosity.

Chronic Ingestion of Coal Fly-Ash Contaminated Prey and Its Effects on Health and Immune Parameters in Juvenile American Alligators (Alligator mississippiensis).

Coal-burning power plants supply approximately 37% of the electricity in the United States. However, incomplete combustion produces ash wastes enriched with toxic trace elements that have historically been disposed of in aquatic basins. Organisms inhabiting such habitats may accumulate these trace elements; however, studies investigating the effects on biota have been primarily restricted to shorter-lived, lower-trophic organisms. The American alligator (Alligator mississippiensis), a long-lived, top-trophic carnivore, has been observed inhabiting these basins, yet the health or immune effects of chronic exposure and possible accumulation remains unknown. In this study, we investigated how chronic dietary ingestion of prey contaminated with coal combustion wastes (CCWs) for 25months, and subsequent accumulation of trace elements present in CCWs, affected juvenile alligator immune function and health. Alligators were assigned to one of four dietary-treatment groups including controls and those fed prey contaminated with CCWs for one, two, or three times a week. However, no effect of Dietary Treatment (p>0.05) was observed on any immune parameter or hematological or plasma analyte we tested. Our results suggest that neither exposure to nor accumulation of low doses of CCWs had a negative effect on certain aspects of the immune and hematological system. However, future studies are required to elucidate this further.

Monitoring of a Reintroduced Population of Juvenile Alligator Snapping Turtles

Reintroduction is a common management tool for conserving imperiled species, but many reintroductions have included little or no postrelease assessment of project success. The alligator snapping turtle (Macrochelys temminckii) is a long-lived species that has experienced significant declines throughout its range, although suitable habitat remains. We report the findings of a reintroduction effort that was initiated in 2008 near the northwestern limit of the species' range. Two hundred forty-six M. temminckii were released into the Caney River and its tributary, Pond Creek, from 2008 to 2010. All turtles exhibited measurable growth by their first recapture 1–3 yrs after release, and no decline in body condition was observed, either in comparison to prerelease body condition or to the condition of animals in the same cohorts that remained in captivity. Apparent survival and recapture probabilities increased with age. Apparent survivorship values were higher for turtles released in the main channel of the Caney River, but recapture probabilities were higher in its tributary. Ultimately, survivorship values may have been influenced by low recapture rates and emigration, in addition to mortality.

Effects of salinity on growth and ion regulation of juvenile alligator gar Atractosteus spatula

The alligator gar (Atractosteus spatula) is a primitive euryhaline fish, found primarily in estuaries and freshwater drainages associated with the northern Gulf of Mexico. The extent of its hypo-osmotic regulatory abilities is not well understood. In order to determine how salinity affects growth rates and ionic and osmoregulation, juvenile alligator gar (330days after hatch; 185g) were exposed to 4 different salinities (0, 8, 16, and 24ppt) for a 30-day period. Specific growth rate, plasma osmolality and ion concentrations, gill and gastrointestinal tract Na+, K+-ATPase activities, and drinking rate were compared. Juvenile alligator gar were able to tolerate hyperosmotic salinities up to 24ppt for a 30day period, albeit with decreased growth resulting largely from decreased food consumption. Plasma osmolality and ionic concentrations were elevated in hyperosmotic salinities, and drinking rates and gastrointestinal tract Na+, K+-ATPase activities increased, particularly in the pyloric caeca, presumably the primary location of water absorption. Therefore, juvenile alligator gar<1year of age are capable of prolonged exposure to hyperosmotic salinities, but, based on the inference of these data, require access to lower salinities for long-term survival.

Feeding Behavior of Captive-Reared Juvenile Alligator Snapping Turtles (Macrochelys temminckii)

Abstract Feeding preference of Macrochelys temminckii (Alligator Snapping Turtle) is not well known. Juveniles reared with no prior exposure to natural prey were tested for innate prey (i.e., fish) preference and foraging ability for mussels in coarse and fine substrates. Alligator Snapping Turtles consumed fish non-selectively, except that they selected Lepomis macrochirus (Bluegill) over Gambusia affinis (Mosquitofish) in live-prey trials, and Lepomis cyanellus (Green Sunfish) over Notemigonus crysoleucas (Golden Shiners) in carrion trials. Juvenile Alligator Snapping Turtles were less active and less successful when foraging for a benthic prey species, Lampsilis siliquoidea (Fatmucket), in coarse substrate than they were when the mussels were in fine and no substrates. Juvenile Alligator Snapping Turtle preference for Bluegill in a controlled environment corresponds to predator and prey habitat associations but could also be influenced by prey (i.e., fish) behavior. Likewise, enhanced activity and prey...

Comparison of Diet Among Reintroduced and Wild Juvenile Alligator Snapping Turtles (Macrochelys temminckii) and Adult Female Ouachita Map Turtles (Graptemys ouachitensis)

Abstract Reintroductions are increasingly utilized in conservation, but the experiences and environments to which animals are exposed prior to release can significantly impact the success of such efforts. We investigated differences in the diet of reintroduced juvenile alligator snapping turtles (Macrochelys temminckii) relative to juveniles from a wild population. In addition, we compared the diet of adult female Ouachita map turtles (Graptemys ouachitensis) to reintroduced M. temminckii with whom co-occurrence was recently reestablished and wild juvenile M. temminckii in a river system where the species have enjoyed long-term sympatry. There were differences in diversity and richness of the diet of M. temminckii at the two study sites that could be due to dissimilarity in foraging experience. There was greater overlap in diet of M. temminckii and G. ouachitensis at the site of reintroduction than at the site of long-term sympatry that corresponded to variation in composition of diet. Such a difference c...

Lung volume and pulmonary compliance in the alligator (Alligator mississippiensis)

Crocodilians have a suite of unique ventilatory features that differ from other reptiles. We examined mechanical aspects of the alligator ventilatory system including maximal lung volume, total static and dynamic pulmonary compliance (lung and body wall) and pressure‐volume hysteresis in juvenile alligators (58 g to 254 g) raised in normoxic environments. Alligators were deeply anesthetized with pentobarbital, decapitated and intubated through the trachea. Lung inflation/deflation cycles were done with an infusion pump; lung pressure was measured with a differential pressure transducer. Lung volume at 15 cm H2O was 257 ml kg−1 which is comparable to other reptiles and amphibians. Maximal static compliance with inflation was 41 ml cm H2O−1 kg−1 and increased to 53 ml cm H2O−1 kg−1 with maximal dynamic compliance. Maximal static and dynamic compliance were greater during deflation (ca. 90 ml cm H2O−1 kg−1). Dynamic compliance was also associated with a six‐fold increase in the hysteresis index compared with static compliance. These data indicate that maximal total compliance in the juvenile alligator is comparable to other terrestrial ectotherms, but significantly greater than mammals. The relatively large lung volume and highly compliant pulmonary system may be important for lung inflation/deflation cycles following spontaneous apneic periods or prolonged dives. Supported by NSF CAREER IOS 0845741 (DAC).

Juvenile Alligator Gar Movement Patterns in a Disconnected Floodplain Habitat in Southeast Missouri

Telemetry is an extremely useful technique used to study movement patterns of fishes to gain insight into life history. This is especially important when dealing with species of conservation concern, such as the alligator gar (Atractosteus spatula). Alligator gar, despite dwindling populations or presumed extirpation across much of its native range, have received minimal attention in the literature. This study sought to evaluate movement patterns of juvenile alligator gar reintroduced to a historic, now disconnected, floodplain of the Mississippi River. Nineteen alligator gar fitted with radio transmitters were stocked into Mingo National Wildlife Refuge during May 2007 and tracked for 1 y. Over the course of the evaluation, 34.9 (se = 5.1) locations per individual gar were recorded and three distinct movement patterns emerged. Thirteen alligator gar (Groups A and B) exhibited site fidelity throughout the study while five alligator gar (Group C) showed highly variable movement patterns; at times showing site fidelity, then exhibiting long-distance movements. When exhibiting site fidelity, alligator gar occupied small areas of Monopoly Marsh or Ditch 5 (Group A: 12.9 ± 6.0 ha, Group B: 4.8 ± 4.9 ha, Group C: 11.8 ± 8.0 ha). Our study demonstrated telemetry of juvenile alligator gar is feasible, various movement patterns (i.e., site fidelity or long-distance movement) exist, and future stockings of juvenile alligator gar are likely to show site fidelity to the area in which they are released.