The effects of climate on annual variation in reproductive output in Snapping Turtles (Chelydra serpentina)

Abstract

Reptiles are highly dependent on climatic patterns to regulate their behavior and physiology, and studies of the effects of climate on the biology of organisms are increasingly important given expected climate change. Our study examined the effects of climate variation over 15 of the 26 years between 1990 and 2015 on the reproductive output of the Snapping Turtle (Chelydra serpentina (Linnaeus, 1758)). Egg mass, clutch size, and clutch mass (relative to body size) were significantly higher in years following warmer temperatures in September and October of the year before reproduction, but not related to temperatures in April and May just before reproduction. Of the above life-history traits, egg mass varied the least across years, and after warm autumns small turtles (225–285 mm carapace length) increased clutch mass by increasing clutch size but not egg mass. In contrast, under the same conditions, large turtles increased clutch mass by increasing egg mass but not clutch size. Our data suggest optimal egg mass may vary with female size. Climate change may already have impacted reproductive output in Snapping Turtles at the site because temperatures during September and October have increased about 0.5 °C each decade for the last 45 years.

Understanding reproductive allometry in turtles: A slippery “slope”

“…The variation among the samples of C. picta and K. flavescens from the same Nebraska field site suggests that annual variation in climate (and associated impacts on resource availability) may be an important factor affecting reproductive allometry (see also Doody et al, ; Iverson & Smith, ). For example, 2012 was the warmest year at the Nebraska site in the 46 years of our records (Iverson, unpublished) and climate has been shown to impact both clutch and egg size (and hence clutch mass) in other turtles (Hedrick, Klondaris, Corichi, Dreslik, & Iverson, ; Iverson & Smith, ; Rollinson, Farmer, & Brooks, ). The effects of annual variation in climate on reproductive output in turtles remain poorly studied, and incorporating that variation in scaling studies will likely be rewarding.…”

Climate effects on nesting phenology in Nebraska turtles

“…Although our study focused on the proximate effects of climate on turtle nesting phenology, its impacts on other areas of life history remain poorly studied (Butler, 2019). For example, climate change is likely to affect the length of the nesting season (e.g., Hedrick et al., 2018; Lamont & Fujisaki, 2014; Pike et al., 2006); internest intervals (Hays et al., 2002); clutch frequency (Mazaris et al., 2012; Tucker et al., 2008); egg and clutch size (Hedrick et al., 2018; Lamont & Fujisaki, 2014; Mazaris et al., 2012); survival of early nests and early nesting females (Mazaris et al., 2009; Schofield et al., 2009); hatching success (Hawkes et al., 2007); posthatching survival (especially in species like Chrysemys picta with hatchlings that overwinter terrestrially; Costanzo et al., 1995; Muir et al., 2012); juvenile growth rates (Avery et al., 1993; Gibbons, 1970); and population sex ratios via temperature‐dependent sex determination (Schwanz & Janzen, 2008; Tucker et al., 2008). None of these potential effects have been examined at our site, nor have the fitness costs of earlier nesting.…”

A Review of the Effects of Climate Change on Chelonians

“…In many temperate turtle species, follicular development begins in the fall, is suspended during the winter, and resumes during the spring, although the relative amount of development during autumn and spring varies between species [75]. Nearly all follicular development in snapping turtles (Chelydra serpentina) occurs during autumn, and warmer temperatures during this season have been linked to increases in egg mass, clutch mass, and clutch size [76]. Climate change can also affect fecundity by changing the accessibility of suitable nesting substrates.…”