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Aiken, SC, United States

The Savannah River Ecology Laboratory is a research unit of the University of Georgia, located at the U.S. Department of Energy's Savannah River Site in Aiken, South Carolina. SREL is supported by federal, state, industry and foundation funding.Since the laboratory's founding in 1951 by Dr. Eugene Odum of the University of Georgia, a pioneer of modern ecology, SREL scientists have conducted long-term environmental studies on the SRS nuclear facility.SREL offers short and long-term educational and research opportunities in ecology and environmental science for graduate and undergraduate students. A wide variety of natural habitat types on the SRS, along with the presence of nuclear and industrial facilities, provides students an exceptional opportunity to study natural and disturbed ecological systems in the same region. Combined with a modern laboratory and field facilities and a diverse natural flora and fauna, SREL offers opportunities for students to develop ecological expertise and for visiting investigators to conduct research. Wikipedia.

I re-examine the phenomenon of delayed timing of emergence from the nest by hatchling turtles (known as overwintering in temperate climates) within the context of the original summary of the topic in an article by Gibbons and Nelson in 1978. I base the overview on cumulative data from research at the Savannah River Ecology Laboratory since 1968 and reports from other locations during the past 34 yr. Investigators have reported known or suspected delayed emergence of hatchling turtles for 43 species, 22 genera, and 8 families from 11 countries and 36 U.S. states and Canadian provinces. The following perspective suggests questions to address and provides recommendations for how herpetologists should proceed in further investigating the phenomenon of hatchling emergence in turtles. The topic is one on which answers must be forthcoming to address turtle conservation on a global scale. For freshwater turtles, which include the majority of the world's turtles, natural selection has favored hatchlings that enter the aquatic habitat at the most propitious season for survival and subsequent growth. Nesting in most species spans several weeks; therefore, at the end of incubation hatchlings must use proximal environmental cues to adjust their timing of departure from the nest and entry into the aquatic habitat. Because of its widespread prevalence, delayed hatchling emergence in a turtle species should be considered the default behavior until evidence to the contrary is provided. Specifically, many turtles emerge several months after hatching, and in temperate climates emergence delayed by up to a year (overwintering) is likely the norm even though conventional wisdom predicts late summer or fall emergence. © 2013 Society for the Study of Amphibians and Reptiles. Source

Belk M.C.,Brigham Young University | Tuckfield R.C.,Savannah River Ecology Laboratory

The reproductive value hypothesis predicts that if residual reproductive value declines as a female ages, then young females should allocate less of available energy to current fecundity and more to future reproduction; whereas, older females should allocate more of available energy to current fecundity and less to future reproduction (i.e. survival). We test the prediction that older female Gambusia affinis exhibit higher levels of allocation to reproduction (i.e. fecundity) and consequently experience greater decline in escape performance (survival cost) during pregnancy compared to young females. Old females had relatively larger clutch wet masses and clutch wet mass increased more during pregnancy compared to young females. Correspondingly, old females exhibit a significant decline in escape velocity over the course of pregnancy; whereas young females show no change in escape velocity throughout pregnancy. Old females have higher escape velocities early in pregnancy and their performance only declines to about the level of performance of young females by the end of pregnancy. Thus, although old females exhibit a greater decline in performance they are better able to ameliorate the cost of decreased performance. © 2009 Oikos. Source

Todd B.D.,University of California at Davis | Scott D.E.,Savannah River Ecology Laboratory | Pechmann J.H.K.,Western Carolina University | Whitfield Gibbons J.,University of California at Davis
Proceedings of the Royal Society B: Biological Sciences

Climate change has had a significant impact globally on the timing of ecological events such as reproduction and migration in many species. Here, we examined the phenology of reproductive migrations in 10 amphibian species at a wetland in South Carolina, USA using a 30 year dataset. We show for the first time that two autumn-breeding amphibians are breeding increasingly later in recent years, coincident with an estimated 1.2°C increase in local overnight air temperatures during the September through February pre-breeding and breeding periods. Additionally, two winter-breeding species in the same community are breeding increasingly earlier. Four of the 10 species studied have shifted their reproductive timing an estimated 15.3 to 76.4 days in the past 30 years. This has resulted in rates of phenological change that range from 5.9 to 37.2 days per decade, providing examples of some of the greatest rates of changing phenology in ecological events reported to date. Owing to the opposing direction of the shifts in reproductive timing, our results suggest an alteration in the degree of temporal niche overlap experienced by amphibian larvae in this community. Reproductive timing can drive community dynamics in larval amphibians and our results identify an important pathway by which climate change may affect amphibian communities. © 2011 The Royal Society. Source

Henningsen J.P.,University of Massachusetts Amherst | Henningsen J.P.,Savannah River Ecology Laboratory | Irschick D.J.,University of Massachusetts Amherst
Functional Ecology

Many animals use signals to resolve disputes over resources. Some signals act as reliable indicators of other traits, such as whole-organism performance or body condition, which may also be important for resolving disputes. Because of the correlations inherent in reliable signals, it is challenging to determine which variables are directly relevant for resolving aggressive interactions. We examined the relationships among dewlap size, bite force and condition, all traits that may be important to conflict resolution in male green anole lizards (Anolis carolinensis). Using a large sample of wild-caught animals, we showed significant positive correlations between dewlap size and maximum bite force capacity, when each trait is corrected for its correlation with body size. We tested the relative importance of each trait to the outcome of interactions in a subset of our sample. We staged dominance encounters between size-matched male green anoles after surgically reducing the dewlap size of one competitor. We show that reducing the size of the dewlap does not significantly change the outcome of staged interactions. Rather, males with higher values of bite force capacity were more likely to win fights. We hypothesize that during close-proximity aggressive interactions, male green anoles use more direct means of assessing one another and that dewlap size functions as a signal of bite force primarily during long-distance territorial displays. Body condition was correlated with bite force, but did not differ significantly between winners and losers. Our results show how an experimental approach can decouple reliable signals from their correlated traits to test which factors influence male contest resolution. © 2011 The Authors. Functional Ecology © 2011 British Ecological Society. Source

Willson J.D.,Savannah River Ecology Laboratory | Willson J.D.,Virginia Polytechnic Institute and State University | Hopkins W.A.,Virginia Polytechnic Institute and State University

Resource availability and accessibility are primary factors guiding the distribution and abundance of organisms. For generalists, prey availability reflects both prey abundance and differences in quality among prey taxa. Although some aspects of prey quality, such as nutritional composition, are well studied, our understanding of how prey morphology contributes to overall prey quality is limited. Because snakes cannot reduce prey size by mastication, many aspects of their feeding ecology (e.g., maximum prey size, feeding performance, and the degree of postprandial locomotor impairment) may be affected by prey shape. We conducted a uniquely comprehensive comparison of prey quality for a generalist species, the banded watersnake (Nerodia fasciata), using prey that were similar in mass and presumably similar in nutritional composition but different in shape and habitat association. Specifically, we compared nutritional composition and shape of paedomorphic salamanders (Ambystoma talpoideum) and sunfish (Lepomis marginatus) and used a series of repeatedmeasures experiments to examine feeding performance (number of prey consumed, maximum prey size, and intra-oral transport time), digestive metabolism (specific dynamic action, SDA), and postprandial locomotor performance of snakes fed Ambystoma and Lepomis. Cost of digestion was similar between the prey types, likely reflecting their similar nutritional composition. However, snakes consumed larger Ambystoma than Lepomis and intra-oral transport time was much shorter for Ambystoma. Snakes fed Lepomis also suffered greater reduction in crawling speed than those fed Ambystoma. These differences highlight the need for behaviorally integrated approaches to understanding prey quality and support field observations of the importance of amphibian prey for juvenile watersnakes. © 2011 by the Ecological Society of America. Source

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