Growth and Condition of American Alligators (Alligator mississippiensis) in an Inland Wetland of East Texas

Saalfeld, David T.; Webb, Kevin K.; Conway, Warren C.; Calkins, Gary E.; Duguay, Jeffrey P.

doi:10.1656/1528-7092-7.3.541

Cited by 27 publications

(23 citation statements)

References 13 publications

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“…An analogous situation is posed by growth studies of Alligator mississippiensis : a large-scale (∼2000 data point) growth study [83] of wild specimens in the Florida Everglades found strong statistical evidence of an increasing growth curve, which the authors interpreted as evidence of indeterminate growth, consistent with other crocodilian growth studies [84]–[86]. Despite this, a recent histological study [87] found the presence of EFS in several captive A. mississippiensis , indicating that, at least in those specimens living in permissive environments, cessation of growth occurred well before death, which is generally interpreted as evidence of determinate growth.…”

Section: Discussionsupporting

confidence: 67%

Revisiting the Estimation of Dinosaur Growth Rates

Myhrvold

2013

PLoS ONE

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Previous growth-rate studies covering 14 dinosaur taxa, as represented by 31 data sets, are critically examined and reanalyzed by using improved statistical techniques. The examination reveals that some previously reported results cannot be replicated by using the methods originally reported; results from new methods are in many cases different, in both the quantitative rates and the qualitative nature of the growth, from results in the prior literature. Asymptotic growth curves, which have been hypothesized to be ubiquitous, are shown to provide best fits for only four of the 14 taxa. Possible reasons for non-asymptotic growth patterns are discussed; they include systematic errors in the age-estimation process and, more likely, a bias toward younger ages among the specimens analyzed. Analysis of the data sets finds that only three taxa include specimens that could be considered skeletally mature (i.e., having attained 90% of maximum body size predicted by asymptotic curve fits), and eleven taxa are quite immature, with the largest specimen having attained less than 62% of predicted asymptotic size. The three taxa that include skeletally mature specimens are included in the four taxa that are best fit by asymptotic curves. The totality of results presented here suggests that previous estimates of both maximum dinosaur growth rates and maximum dinosaur sizes have little statistical support. Suggestions for future research are presented.

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Section: Discussionsupporting

confidence: 67%

Revisiting the Estimation of Dinosaur Growth Rates

Myhrvold

2013

PLoS ONE

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“…For small M. niger, we used a Richards monomolecular growth model (Abercrombie, 1996;Wilkinson and Rhodes, 1997;Saalfeld et al, 2008). However, there was no detectable relationship between age and growth rate in larger M. niger, making use of the Richards growth model impossible.…”

Section: Data Collection and Analysesmentioning

confidence: 99%

“…Most studies of crocodilian growth patterns have been based on mark-recapture studies and the relationship between growth rate and the size of individuals (Magnusson and Sanaiotti, 1995;Dalrymple, 1996;Saalfeld et al, 2008). This information is generally analyzed using sigmoidal growth models to describe the relationship between size and age of individuals (Andrews, 1982).…”

Section: Introductionmentioning

confidence: 99%

“…For management, it is not appropriate to model between-site variation in parameters as a random variable because management generally has to be tailored to each site and no general decision should be made across all sites. External factors that could cause such variation include climate (Wilkinson and Rhodes, 1997) and ecosystem productivity (Saalfeld et al, 2008). However, densitydependent processes also affect demography (Abercrombie, 1989).…”

Section: Introductionmentioning

confidence: 99%

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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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“…Body condition indices, defined by a mass and length relationship, have been used in a number of crocodilian studies (Bagenal & Tesch, 1978;Taylor, 1979;Brandt, 1991;Elsey et al, 1992;Dalrymple, 1996;Barr, 1997;Saalfeld et al, 2008). We used Fulton's condition factor (K) as it was previously used in studies of the American alligator (Barr, 1997;Rice et al, 2007).…”

Section: Morphometric and Water Depth Measurementsmentioning

confidence: 99%

Relationship between body condition of American alligators and water depth in the Everglades, Florida

Fujisaki

Rice

Pearlstine³

et al. 2009

Hydrobiologia

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Feeding opportunities of American alligators (Alligator mississippiensis) in freshwater wetlands in south Florida are closely linked to hydrologic conditions. In the Everglades, seasonally and annually fluctuating surface water levels affect populations of aquatic organisms that alligators consume. Since prey becomes more concentrated when water depth decreases, we hypothesized an inverse relationship between body condition and water depth in the Everglades. On average, condition of adult alligators in the dry season was significantly higher than in the wet season, but this was not the case for juveniles/ subadults. The correlation between body condition and measured water depth at capture locations was weak; however, there was a significant negative correlation between the condition and predicted water depth prior to capture for all animals except for spring juveniles/subadults which had a weak positive condition-water depth relationship. Overall, a relatively strong inverse correlation occurred at 10-49 days prior to the capture day, suggesting that current body condition of alligators may depend on feeding opportunities during that period. Fitted regression of body condition on water depth (mean depth of 10 days when condition-water depth correlation was greatest) resulted in a significantly negative slope, except for spring adult females and spring juveniles/subadults for which slopes were not significantly different from zero. Our results imply that water management practices may be critical for alligators in the Everglades since water depth can affect animal condition in a relatively short period of time.

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Growth and Condition of American Alligators (Alligator mississippiensis) in an Inland Wetland of East Texas

Cited by 27 publications

References 13 publications

Revisiting the Estimation of Dinosaur Growth Rates

Revisiting the Estimation of Dinosaur Growth Rates

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

Relationship between body condition of American alligators and water depth in the Everglades, Florida

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