St Augustine Alligator Farm Zoological Park

Saint Augustine, FL, United States

St Augustine Alligator Farm Zoological Park

Saint Augustine, FL, United States
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Erickson G.M.,Florida State University | Gignac P.M.,Florida State University | Steppan S.J.,Florida State University | Lappin A.K.,California State Polytechnic University, Pomona | And 5 more authors.
PLoS ONE | Year: 2012

Background: Crocodilians have dominated predatory niches at the water-land interface for over 85 million years. Like their ancestors, living species show substantial variation in their jaw proportions, dental form and body size. These differences are often assumed to reflect anatomical specialization related to feeding and niche occupation, but quantified data are scant. How these factors relate to biomechanical performance during feeding and their relevance to crocodilian evolutionary success are not known. Methodology/Principal Findings: We measured adult bite forces and tooth pressures in all 23 extant crocodilian species and analyzed the results in ecological and phylogenetic contexts. We demonstrate that these reptiles generate the highest bite forces and tooth pressures known for any living animals. Bite forces strongly correlate with body size, and size changes are a major mechanism of feeding evolution in this group. Jaw shape demonstrates surprisingly little correlation to bite force and pressures. Bite forces can now be predicted in fossil crocodilians using the regression equations generated in this research. Conclusions/Significance: Critical to crocodilian long-term success was the evolution of a high bite-force generating musculo-skeletal architecture. Once achieved, the relative force capacities of this system went essentially unmodified throughout subsequent diversification. Rampant changes in body size and concurrent changes in bite force served as a mechanism to allow access to differing prey types and sizes. Further access to the diversity of near-shore prey was gained primarily through changes in tooth pressure via the evolution of dental form and distributions of the teeth within the jaws. Rostral proportions changed substantially throughout crocodilian evolution, but not in correspondence with bite forces. The biomechanical and ecological ramifications of such changes need further examination. © 2012 Erickson et al.

Erickson G.M.,Florida State University | Gignac P.M.,Florida State University | Gignac P.M.,Oklahoma State University | Lappin A.K.,California State Polytechnic University, Pomona | And 4 more authors.
Journal of Zoology | Year: 2014

Interspecific adult bite forces for all extant crocodylian species are now known. However, how bite forces scale during ontogeny across the clade has yet to be studied. Here we test the hypotheses that extant crocodylians share positively allometric and statistically comparable developmental scaling coefficients for maximal bite-force capacity relative to body size. To do this, we measured bite forces in the Australian freshwater crocodile Crocodylus johnsoni and the Saltwater crocodile C.porosus, and determined how performance changed during ontogeny. We statistically compared these results with those for the American alligator Alligator mississippiensis using 95% prediction intervals and interpreted our findings in a phylogenetic context. We found no observable taxon-specific shifts in the intraspecific scaling of biomechanical performance. Instead, all bite-force values in our crocodylid dataset fell within the bounds of the A.mississippiensis 95% prediction intervals, suggesting similar bite-force capacity when same-sized individuals are compared. This holds true regardless of differences in developmental stage, potential adult body size, rostro-dental form, bone mineralization, cranial suturing, dietary differences or phylogenetic relatedness. These findings suggest that intraspecific bite-force scaling for crocodylians with feeding ecologies comparable with those of extant forms has likely remained evolutionarily static during their diversification. copy; 2013 The Zoological Society of London.

Dinets V.,University of Tennessee at Knoxville | Brueggen J.C.,St Augustine Alligator Farm Zoological Park | Brueggen J.D.,St Augustine Alligator Farm Zoological Park
Ethology Ecology and Evolution | Year: 2015

Using objects as hunting lures is very rare in nature, having been observed in just a handful of species. We report the use of twigs and sticks as bird lures by two crocodilian species. At least one of them uses this method predominantly during the nest-building season of its prey. This is the first known case of a predator not just using objects as lures, but also taking into account the seasonality of prey behavior. It provides a surprising insight into previously unrecognized complexity of archosaurian behavior. © 2013 Dipartimento di Biologia, Università di Firenze, Italia.

PubMed | University of Vienna, St Augustine Alligator Farm Zoological Park and Kyoto University
Type: Journal Article | Journal: The Journal of experimental biology | Year: 2015

Crocodilians are among the most vocal non-avian reptiles. Adults of both sexes produce loud vocalizations known as bellows year round, with the highest rate during the mating season. Although the specific function of these vocalizations remains unclear, they may advertise the callers body size, because relative size differences strongly affect courtship and territorial behaviour in crocodilians. In mammals and birds, a common mechanism for producing honest acoustic signals of body size is via formant frequencies (vocal tract resonances). To our knowledge, formants have to date never been documented in any non-avian reptile, and formants do not seem to play a role in the vocalizations of anurans. We tested for formants in crocodilian vocalizations by using playbacks to induce a female Chinese alligator (Alligator sinensis) to bellow in an airtight chamber. During vocalizations, the animal inhaled either normal air or a helium/oxygen mixture (heliox) in which the velocity of sound is increased. Although heliox allows normal respiration, it alters the formant distribution of the sound spectrum. An acoustic analysis of the calls showed that the source signal components remained constant under both conditions, but an upward shift of high-energy frequency bands was observed in heliox. We conclude that these frequency bands represent formants. We suggest that crocodilian vocalizations could thus provide an acoustic indication of body size via formants. Because birds and crocodilians share a common ancestor with all dinosaurs, a better understanding of their vocal production systems may also provide insight into the communication of extinct Archosaurians.

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