Survivorship and Predation of Hatchling and Yearling Gopher Tortoises, Gopherus polyphemus

Butler, Joseph A.; Sowell, Scott

doi:10.2307/1565195

Cited by 41 publications

(28 citation statements)

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“…In support of these notions, many young tortoises were recaptured under the slabs, and we did not find any injured juveniles under the artificial refuges. The safety offered by artificial refuges might represent a means to improve juvenile survival, especially during the crucial early post-hatehling period (Butler and Sowell, 1996;Pike and Seigel, 2006;Tomillo et al, 2010;Bolten et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

Fibrocement slabs as useful tools to monitor juvenile reptiles: a study in a tortoise species

Ballouard¹,

Sébastien²,

Lafon³

et al. 2013

Amphib Reptilia

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bstract. Most species of tortoises are seriously threatened worldwide. Chelonians are long-lived organisms characterized by slow detnographic traits; mathematical modeling estimated that a high rate of juvenile annual survival (i.e. >0.6 on average) is essential for the persistence of populations. Unfortunately, current knowledge about free-ranging juveniles is fragmentary. Under field conditions, young tortoises are very secretive, they remain sheltered beneath bushes, and they escape capture. The resulting lack of information impairs the assessment of key parameters such as juvenile survival, habitat use, or recruitment rate and thus seriously impedes both accurate population viability analyses and conservation planning. Large-scale monitoring of different populations of a threatened species (Te.mido hermwmi hermanni) confirmed that juveniles are rarely seen in the field. In 2011, we placed corrugated fibrocement slabs as alternative refuges for small tortoises in a densely vegetated study site. Many juveniles sheltered under the space offered by tbe corrugations; consequently they were easily captured and recaptured. Our results suggest that this simple technique may significantly improve the detectability of juveniles, providing access to the life history traits of this otherwise elusive age cohort. The slabs also provide protection against predators (such as dogs and birds) which further suggests that these refuges may also improve the survival of tbe smallest and most vulnerable individuals.

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Section: Discussionmentioning

confidence: 99%

Fibrocement slabs as useful tools to monitor juvenile reptiles: a study in a tortoise species

Ballouard¹,

Sébastien²,

Lafon³

et al. 2013

Amphib Reptilia

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“…However, when data are limited, the feasible demography approach can be used to develop estimates for poorly known demographic traits (e.g., juvenile survivorship) based on values of other demographic variables for which better estimates are available. In this model, it was estimated that annual juvenile survivorship must average approximately 75 percent over the juvenile period to produce a stable population -a value much higher than generally reported in the literature for the early juvenile years i.e., ages 0-4 (Butler and Sowell 1996;Epperson and Heise 2003;Pike and Seigel 2006;Wilson 1991;Tuberville et al 2008 [in review]). The feasible demography approach reveals that the combination of parameters used in VORTEX ® are unlikely to produce a stable population under any of the scenarios modeled.…”

Section: Demographic Feasibility Analysismentioning

confidence: 97%

“…In addition, tortoises are difficult to accurately age once they reach reproductive maturity and most studies have focused on adults, further limiting the information on age-specific survivorship of gopher tortoises. Hatchling survivorship rates were based on radio-telemetry studies of hatchlings (Butler and Sowell 1996;Epperson and Heise 2003;Pike and Seigel 2006). Juvenile survivorship rates were based on a radio-telemetry study by Wilson (1991).…”

Section: Distribution Of Number Of Offspring Per Female Per Year -Normentioning

confidence: 99%

“…Based on comparison of results from studies of gopher tortoise hatchlings (Pike and Seigel 2006;Butler and Sowell 1996;Epperson and Heise 2003) and older juveniles (Wilson 1991;Tuberville et al, 2008 [in review]), survivorship of juveniles varies over the juvenile period, increasing with size and/or age. For simplicity, however, it was assumed that annual survivorship was consistent throughout the juvenile period and lower than in adults.…”

Section: Demographic Feasibility Analysismentioning

confidence: 99%

“…Hatchling mortality rates have been reported in three published radiotelemetry studies from Florida and Mississippi (Butler and Sowell 1996;Epperson and Heise 2003;Pike and Seigel 2006). The naturally high mortality rates combined with the intensive nature of radio-telemetry studies make it difficult, however, to obtain sample sizes large enough to estimate hatchling survivorship and its variability accurately (Pike and Seigel 2006).…”

Section: Comparative Survivorship Of Immature Stagesmentioning

confidence: 99%

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Estimating Viability of Gopher Tortoise Populations

Tuberville¹,

Gibbons²,

Balbach³

2009

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Although the gopher tortoise (Gopherus polyphemus) is widespread across the southeastern United States where conditions are favorable, the species is in serious decline. While biologists and land managers might consider any of a variety of in-situ and ex-situ management options when determining how best to manage individual populations, there are no good decision tools for evaluating or predicting whether the existing population is viable in the long term. This study developed demographic models for gopher tortoise populations and has proposed to use those models to predict outcomes for a variety of population conditions and management scenarios. The major limiting factor in the development of models was the availability of complete lifehistory data. Because of its demonstrated importance in population stability in other turtle species, adult survivorship was assumed to be high in all model scenarios. However, reproduction and survivorship of other life stages varied among simulations. The model results demonstrated that, of the parameters manipulated, hatchling survivorship was the most critical life history stage because of the very small likelihood that hatchlings survive to their second year. Any management actions that increase hatchling success are likely to increase population viability significantly.

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Effect of nest location on gopher tortoise nest survival

et al. 2016

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Gopher tortoise (Gopherus polyphemus) populations are declining range‐wide primarily because of habitat loss, fragmentation, and degradation, but low recruitment due to nest predation also may be contributing to this decline. The relationship of nest location and nest survival is unknown. Therefore, our objective was to determine whether nest location influenced depredation risk and potential recruitment success. Between 30 May 2013 and 3 September 2014, we constructed and monitored 105 artificial gopher tortoise nests (45 in 2013 and 60 in 2014) with 35 nests at each of 3 classifications of nest sites: within active burrow aprons (i.e., the mound of sand at the burrow entrance), inactive burrow aprons, and open sandy sites. Using the artificial nests, we investigated the influence of nest site classification, distance to road, and prescribed fire frequency (<1 year and 1 year since burn) on gopher tortoise nest survival. Additionally, we monitored 21 natural nests at burrow aprons to assess predation patterns as compared to artificial nests. Seventy‐two (57%) of 126 nests were fully depredated during the study, and predation rates at artificial and natural nests were similar. We identified predators at 48 nests using trail cameras; the nine‐banded armadillo (Dasypus novemcinctus) was the primary nest predator (69%). Nests in open sandy areas away from burrows exhibited greater daily survival rates (DSR; 0.991 ± 0.005 SE) compared to nests in burrow aprons (active burrow aprons: 0.967 ± 0.018; inactive burrow aprons: 0.949 ± 0.027). Additionally, nests at locations burned the year of the study had a lower chance of survival (DSR: 0.959 ± 0.022) than nests at locations burned the previous year (DSR: 0.991 ± 0.005). Management practices that maintain open sandy areas (e.g., prescribed fire) away from burrows may increase tortoise nest survival. Fire return intervals of >1 year that are implemented frequently enough to maintain open sandy areas would be beneficial to nesting tortoises. © 2016 The Wildlife Society.

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Survivorship and Predation of Hatchling and Yearling Gopher Tortoises, Gopherus polyphemus

Cited by 41 publications

References 0 publications

Fibrocement slabs as useful tools to monitor juvenile reptiles: a study in a tortoise species

Fibrocement slabs as useful tools to monitor juvenile reptiles: a study in a tortoise species

Estimating Viability of Gopher Tortoise Populations

Effect of nest location on gopher tortoise nest survival

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