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ESR 46:215-226 (2021)  -  DOI:

Warming conditions boost reproductive output for a northern gopher tortoise population

Elizabeth A. Hunter1,*, Kevin J. Loope2, K. Kristina Drake3, Kaitlyn Hanley2, Douglas N. Jones Jr. 2,5,#, Kevin T. Shoemaker4, David C. Rostal2

1US Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Department of Fish and Wildlife Conservation, Virginia Tech, 310 W. Campus Dr., Blacksburg, VA 24061, USA
2Department of Biology, Georgia Southern University, 1332 Southern Dr., Statesboro, GA 30458, USA
3US Geological Survey, Western Ecological Research Center, 160 N. Stephanie Dr., Henderson, NV 89074, USA
4Department of Natural Resources and Environmental Science, University of Nevada - Reno, 1664 N. Virginia St., Reno, NV 89557, USA
5Present address: US Environmental Protection Agency, Region 7, 11201 Renner Blvd., Lenexa, KS 66219, USA

*Corresponding author:
#The research presented was not performed or funded by EPA and was not subject to EPA’s quality system requirements. The co-author is not doing this work in any governmental capacity. The views expressed in this article are those of the author(s) and do not necessarily represent the views or the policies of the US EPA

ABSTRACT: The effects of climate change on at-risk species will depend on how life history processes respond to climate and whether the seasonal timing of local climate changes overlaps with species-specific windows of climate sensitivity. For long-lived, iteroparous species like gopher tortoises Gopherus polyphemus, climate likely has a greater influence on reproduction than on adult survival. Our objective was to estimate the timing, magnitude, and direction of climate-driven effects on gopher tortoise reproductive output using a 25 yr dataset collected in southeastern Georgia, USA, near the northern edge of the species’ range. We assessed the timing of climate effects on reproductive output (both probability of reproduction and clutch size) by fitting models with climate covariates (maximum temperature, precipitation, and temperature range) summarized at all possible time intervals (in 1 mo increments) within the 24 mo period prior to the summer census date. We then fit a final model of reproductive output as a function of the identified climate variables and time windows using a Bayesian mixture model. Probability of reproduction was positively correlated with the prior year’s April-May maximum temperature, and clutch size was positively correlated with the prior year’s June maximum temperature. April-May and June maximum temperatures have increased over the past 3 decades at the study site, which likely led to an increase in clutch size of approximately 1 egg (15% increase over a mean of 6.5 eggs). However, the net effect of climate change on gopher tortoise population dynamics will depend on whether there are opposing or reinforcing climate responses for other demographic rates.

KEY WORDS: Climate change · Clutch size · Fecundity · Gopherus polyphemus · Turtles

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Cite this article as: Hunter EA, Loope KJ, Drake KK, Hanley K, Jones DN Jr , Shoemaker KT, Rostal DC (2021) Warming conditions boost reproductive output for a northern gopher tortoise population. Endang Species Res 46:215-226.

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