Growth Rates of American Alligators in Estuarine and Palustrine Wetlands in Louisiana

Rootes, W. L.; Chabreck, Robert H.; Wright, Vernon L.; Brown, Bobby W.; Hess, Thomas J.

doi:10.2307/1352272

Cited by 58 publications

(41 citation statements)

References 16 publications

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“…insect (Lampert and Trubetskova, 1996); reptile (Sinervo and Adolph, 1989); mammal (Kraus et al, 2005); bird (Richner, 1989)]. Alligator growth can be highly variable, and dependent upon environment, life history and food availability (Coulson et al, 1973;Chabreck and Joanen, 1979;Jacobsen and Kushlan, 1989;Rootes et al, 1991;Elsey et al, 1992). For example, a population of wild, 1 year old alligators can weigh less than 0.5kg, whereas artificially high temperatures and unlimited access to food can allow pen-reared, 1 year old alligators to weigh 7kg (Coulson et al, 1973).…”

Section: Surgical Removal Of R-l Cardiac Shunt Does Not Greatly Affecmentioning

confidence: 99%

“…In our laboratory population of alligators fed a diet of chicken and goldfish, mean body mass for all animals at 1 year of age was a relatively small ~200g, but mean body mass for all animals at 2 years of age was ~1.3kg. Reproductive maturity in crocodilians is based on size, not age (Rootes et al, 1991), and higher growth rates could increase fitness, with alligators reaching reproductive size more quickly. If R-L cardiac shunt conferred a strong adaptive advantage to crocodilians, one would expect a large and consistent decrement in growth to be apparent in all animals with their LAo occluded.…”

Section: Surgical Removal Of R-l Cardiac Shunt Does Not Greatly Affecmentioning

confidence: 99%

“…Male and female alligators have been reported to reach sexual maturity at the same size, 1.83m total length or approximately 0.915m SVL (Rootes et al, 1991), though growth for female alligators can be reduced compared with that of male alligators, particularly approaching and following sexual maturity (Chabreck and Joanen, 1979). Fitness calculations would be impractical in the present study, as they require fecundity measures over multiple generations, and alligators can take >5 years to reach reproductive maturity.…”

Section: Growth R-l Cardiac Shunt and The Potential Impact On Alligamentioning

confidence: 99%

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Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Eme

Gwalthney

Owerkowicz

et al. 2010

Journal of Experimental Biology

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SUMMARYThe functional and possible adaptive significance of non-avian reptiles' dual aortic arch system and the ability of all non-avian reptiles to perform central vascular cardiac shunts have been of great interest to comparative physiologists. The unique cardiac anatomy of crocodilians -a four-chambered heart with the dual aortic arch system -allows for only right-to-left (R-L; pulmonary bypass) cardiac shunt and for surgical elimination of this shunt. Surgical removal of the R-L shunt, by occluding the left aorta (LAo) upstream and downstream of the foramen of Panizza, results in a crocodilian with an obligatory, avian/mammalian central circulation. In this study, R-L cardiac shunt was eliminated in age-matched, female American alligators (Alligator mississippiensis; 5-7 months of age). We tested the hypothesis that surgical elimination of R-L cardiac shunt would impair growth (a readily measured proxy for fitness) compared with sham-operated, age-matched controls, especially in animals subjected to exhaustive exercise. While regular exercise caused a decrease in size (snout-to-vent length, head length and body mass), elimination of the capacity for R-L cardiac shunt did not greatly reduce animal growth, despite a chronic ventricular enlargement in surgically altered juvenile alligators. We speculate that, despite being slightly smaller, alligators with an occluded LAo would have reached sexual maturity in the same breeding season as control alligators. This study suggests that crocodilian R-L cardiac shunt does not provide an adaptive advantage for juvenile alligator growth and supports the logic that cardiac shunts persist in crocodilians because they have not been selected against. Supplementary material available online at

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Section: Surgical Removal Of R-l Cardiac Shunt Does Not Greatly Affecmentioning

confidence: 99%

Section: Surgical Removal Of R-l Cardiac Shunt Does Not Greatly Affecmentioning

confidence: 99%

Section: Growth R-l Cardiac Shunt and The Potential Impact On Alligamentioning

confidence: 99%

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Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Eme

Gwalthney

Owerkowicz

et al. 2010

Journal of Experimental Biology

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“…Ectotherms, although frequently thought of as primitive (2), are actually specialists in coping with low levels of available energy (3,4). Ectotherm vertebrates have slow and flexible growth rates and a notable physiological plasticity, which allows a close matching of their energy requirements to prevailing resource conditions (3,5,6). Endotherms, instead, typically have high and steady growth rates and a constant thermometabolic regime, and they depend on high and continuous food intake to maintain their elevated metabolism (7).…”

mentioning

confidence: 99%

Physiological and life history strategies of a fossil large mammal in a resource-limited environment

Köhler

Moyà‐Solà

2009

Proc. Natl. Acad. Sci. U.S.A.

129

116

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Because of their physiological and life history characteristics, mammals exploit adaptive zones unavailable to ectothermic reptiles. Yet, they perform best in energy-rich environments because their high and constant growth rates and their sustained levels of resting metabolism require continuous resource supply. In resourcelimited ecosystems such as islands, therefore, reptiles frequently displace mammals because their slow and flexible growth rates and low metabolic rates permit them to operate effectively with low energy flow. An apparent contradiction of this general principle is the long-term persistence of certain fossil large mammals on energy-poor Mediterranean islands. The purpose of the present study is to uncover the developmental and physiological strategies that allowed fossil large mammals to cope with the low levels of resource supply that characterize insular ecosystems. Long-bone histology of Myotragus, a Plio-Pleistocene bovid from the Balearic Islands, reveals lamellar-zonal tissue throughout the cortex, a trait exclusive to ectothermic reptiles. The bone microstructure indicates that Myotragus grew unlike any other mammal but similar to crocodiles at slow and flexible rates, ceased growth periodically, and attained somatic maturity extremely late by Ϸ12 years. This developmental pattern denotes that Myotragus, much like extant reptiles, synchronized its metabolic requirements with fluctuating resource levels. Our results suggest that developmental and physiological plasticity was crucial to the survival of this and, perhaps, other large mammals on resource-limited Mediterranean Islands, yet it eventually led to their extinction through a major predator, Homo sapiens.islands ͉ artiodactyl ͉ paleohistology ͉ growth rate ͉ metabolism

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“…Chabreck and Joanen, 1979;Brandt, 1991;Elsey et al, 1992). We used studies in Louisiana (Rootes et al, 1991) and South Carolina (Wilkinson and Rhodes, 1997) to illustrate growth in this species because they represent geographical and climatic extremes of the species range, and provided detailed data on males and females separately.…”

Section: Data Collection and Analysesmentioning

confidence: 99%

Growth rates of black caiman (Melanosuchus niger) and spectacled caiman (Caiman crocodilus) from two different Amazonian flooded habitats

et al. 2013

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Rates of growth and survival in wild populations are affected by the physical environment, biotic interactions, and density-dependent processes, such as growth and fecundity. However, the relative importance of these factors in longlived reptiles is poorly understood. We analyzed growth rates oí Melanosuchus niger and Caiman crocodilus coexisting in two areas of the Brazilian Amazon with very different environmental characteristics. Growth rates of Caiman crocodilus at the two sites were similar, but M. niger grew more slowly in the area with higher productivity and higher density of caimans. Growth rates of the same species from other sites and of the temperate-zone Alligator mississippiensis indicate large differences among sites, but little evidence that these differences are primarily due to differences in productivity or temperature. Demographic models used to estimate sustained yields from caiman harvests should take into account the likely importance of density-dependent growth.

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Growth Rates of American Alligators in Estuarine and Palustrine Wetlands in Louisiana

Cited by 58 publications

References 16 publications

Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Turning crocodilian hearts into bird hearts: growth rates are similar for alligators with and without right-to-left cardiac shunt

Physiological and life history strategies of a fossil large mammal in a resource-limited environment

Growth rates of black caiman (Melanosuchus niger) and spectacled caiman (Caiman crocodilus) from two different Amazonian flooded habitats

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