Skip to main content
U.S. flag

An official website of the United States government

Warming conditions boost reproductive output for a northern gopher tortoise population

December 2, 2021

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.

Publication Year 2022
Title Warming conditions boost reproductive output for a northern gopher tortoise population
DOI 10.3354/esr01155
Authors Elizabeth Ann Hunter, Kevin J. Loope, K. Kristina Drake, Kaitlyn Hanley, Douglas N. Jones, Kevin T. Shoemaker, David C. Rostal
Publication Type Article
Publication Subtype Journal Article
Series Title Endangered Species Research
Index ID 70229712
Record Source USGS Publications Warehouse
USGS Organization Coop Res Unit Leetown