Status of the Alligator Snapping Turtle (<i>Macrochelys temminckii</i>) in South Alabama with Comments on Its Distribution

Folt, Brian; Godwin, James C.

doi:10.2744/ccb-1036.1

Cited by 21 publications

(45 citation statements)

References 13 publications

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“…In the absence of studies on verified unharvested populations, natural demographics and population structure are unknown for Macrochelys (Boundy and Kennedy 2006;Folt and Godwin 2013), but we suggest that our results from Spring Creek provide the best representation of reference demography for Macrochelys available to date. First, the observed and estimated population structure was characterized by an even sex ratio and a greater proportion of adults than juveniles.…”

Section: Discussionmentioning

confidence: 83%

Establishing Reference Demography for Conservation: A Case Study ofMacrochelys temminckiiin Spring Creek, Georgia

Folt

Jensen

Teare

et al. 2016

Herpetological Monographs

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The conservation of large, long-lived turtle species can be a challenging issue because their life-history strategies make populations sensitive to changes in adult survivorship and populations may be difficult to sample. The Alligator Snapping Turtle (Macrochelys temminckii) is a large freshwater turtle species occurring in North America for which commercial harvest has severely reduced populations throughout the species range. Given recent population declines and a general deficit of demographic knowledge for Macrochelys, we conducted a mark-recapture study of M. temminckii from 1997-2013 in Spring Creek, Georgia, USA. We made 166 captures of 75 individuals using baited hoop-net traps and skindiving searches. The observed and estimated population structure described the adult sex ratio as even and adults as more abundant than juveniles. Apparent survival was higher for adult males (0.98) and females (0.95) than for juveniles (0.86), and we estimated a population density of 13-14 turtles/stream kilometer. The survival estimates for adult M. temminckii are among the highest of all freshwater turtle species reported in the literature. We used the empirical demographic parameters described here and a literature review to build an updated population model for M. temminckii; the model estimated a finite rate of population increase consistent with a growing population (k ¼ 1.036) at Spring Creek, and population viability analysis found the population growing over the next 50 yr in 100% of simulations. Application of our model to published survival estimates from two impacted western populations indicated a declining population (k ¼ 0.563) with a high risk of extirpation in Oklahoma and a population with a slow rate of decline (k ¼ 0.978) but approaching stability in Arkansas. Simulations identified combinations of survival values which generate viable populations and also characterized population structure resulting from viable scenarios. This is the first study to document a stable and viable population of Macrochelys. We suggest that the population parameters described at Spring Creek are the best approximation of reference demographic conditions for Macrochelys to date, and this study provides a general framework applicable for large, long-lived, endangered turtle species for which demographic data are unavailable.

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Section: Discussionmentioning

confidence: 83%

Establishing Reference Demography for Conservation: A Case Study ofMacrochelys temminckiiin Spring Creek, Georgia

Folt

Jensen

Teare

et al. 2016

Herpetological Monographs

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“…data, 2011). Folt and Godwin (2013) observed female-biased sex ratios in their survey of M. temminckii in south Alabama but were unable to attribute a cause. We are also uncertain about the cause of our observed sex ratios in the SFR.…”

Section: Discussionmentioning

confidence: 87%

“…Using mean CL as a measure of body size, the SDI reported for M. apalachicolae is 20.38 (Teare 2010), and values for M. temminckii range from 20.15 to 20.24 (Dobie 1971;Sloan et al 1996;Boundy and Kennedy 2006;Bogosian 2010;Folt and Godwin 2013;Howey and Dinkelacker 2013). Thus, male Macrochelys are on average 15-38% larger than females.…”

Section: Discussionmentioning

confidence: 95%

Population Structure and Body Size of the Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis) in Northern Florida

Johnston

Thomas

Suarez

et al. 2015

Chelonian Conservation and Biology

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Macrochelys suwanniensis is a newly described species endemic to the Suwannee River drainage in the southeastern United States. We conducted a study of M. suwanniensis in the Santa Fe River (SFR), the major Florida tributary of the Suwannee River, between 2004 and 2011. We captured 109 individuals (24% immature, 44% adult female, 32% adult male). Adult males (mean straight midline carapace length [CL] = 530.7 mm, mean mass = 34.0 kg) were significantly larger than adult females (mean CL = 424.0 mm, mean mass = 17.2 kg), with a sexual size dimorphism index of 20.25 based on mean CL. The largest turtle in our study was 623 mm CL and weighed 54.4 kg. Adult females were significantly larger (CL) in the lower SFR than in the upper SFR (these reaches are separated where the river flows underground for 5 km). All adult males . 600 mm CL were captured in the lower SFR. Adult females were proportionately heavier in the upper SFR than in the lower SFR; males did not show this difference. We hypothesize that these differences in body size are related to habitat. The M. suwanniensis population in the SFR presently appears healthy, but we suggest this species requires continued protection because of vulnerability of adults to harvest.

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“…Catch per unit effort did show a clear latitudinal pattern in relative abundance across the study area, which was corroborated after quantifying false-negative error rate. This suggests that alligator snapping turtle hoop trap surveys standardized only by use of CPUE (Folt and Godwin 2013, Lescher et al 2013, King et al 2016, Huntzinger et al 2019) are capable of capturing general patterns in relative abundance, albeit with biases that arise from other sources of inter-survey and inter-site heterogeneity. Our data provide little support that abundance of the species declines at longitudes closer to its western range edge in the state.…”

Section: Determinants Of Distributional Patternsmentioning

confidence: 99%

“…Hoop trap surveys have contributed much of the current ecological understanding of patterns in distribution and abundance of the alligator snapping turtle (Macrochelys temminckii) (Jensen and Birkhead 2003, Riedle et al 2005, Boundy and Kennedy 2006, Howey and Dinkelacker 2013, Huntzinger et al 2019. Many studies using these surveys assume CPUE to be an adequate proxy of relative abundance (Folt and Godwin 2013, Lescher et al 2013, King et al 2016, Huntzinger et al 2019. With a few exceptions (Dreslik et al 2017, Johnson 2020, hoop trap surveys do not explicitly account for environmentally caused variation in p. As potential sources of such variation, there is evidence alligator snapping turtles may decrease activity and be captured at lower rates during temperature extremes brought about during summer and winter (Riedle et al 2006, Fitzgerald and Nelson 2011, Munscher et al 2020), and Pritchard (2006 reported an anecdote that capture rate of the species decreased during bright, full moon nights.…”

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confidence: 99%

Detection, occupancy, and abundance of the alligator snapping turtle in Texas

et al. 2023

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The alligator snapping turtle (Macrochelys temminckii) is a long‐lived species that is widely distributed across the southeastern United States. Both these characteristics make monitoring its occupancy and abundance particularly challenging. In 2020 and 2021, we conducted hoop trap surveys at 51 permanent water bodies across the Texas, USA, range of the species to estimate occupancy and average abundance with site occupancy models and multinomial N‐mixture models, respectively. We confirmed the species to be present at 61% of surveyed locations. Mean detection probability was 0.77, and was influenced methodologically by the spacing of traps, and environmentally by lunar phase and water flow velocity. Mean occupancy probability was 0.82, and mean estimated abundance was 7.57 turtles/site. Our data provided evidence that the species has a higher occurrence probability in waters of highly forested catchments, and is most probable to occur in highest abundances at median latitudes within its Texas range. Despite known microhabitat preferences of the species, instream habitat characteristics (e.g., canopy coverage, depth, sinuosity) did not strongly influence its occupancy or abundance. Spatial dynamics of the occupancy and abundance of the species in Texas are influenced by landscape features more than local habitat. These results further corroborate the importance of watershed land cover to aquatic organisms, and our methods provide a standardized template for monitoring and quantifying important demographic parameters of the species across multiple locations while accounting for imperfect detection.

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Status of the Alligator Snapping Turtle (Macrochelys temminckii) in South Alabama with Comments on Its Distribution

Cited by 21 publications

References 13 publications

Establishing Reference Demography for Conservation: A Case Study ofMacrochelys temminckiiin Spring Creek, Georgia

Establishing Reference Demography for Conservation: A Case Study ofMacrochelys temminckiiin Spring Creek, Georgia

Population Structure and Body Size of the Suwannee Alligator Snapping Turtle (Macrochelys suwanniensis) in Northern Florida

Detection, occupancy, and abundance of the alligator snapping turtle in Texas

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