SREL Reprint #2043

 

 

 

EFFECTS OF SUPPLEMENTAL FEEDING AND THERMAL
ENVIRONMENT ON GROWTH RATES OF EASTERN
FENCE LIZARDS, SCELOPORUS UNDULATUS


PETER H. NIEWIAROWSKI
Leidy Laboratory, University of Pennsylvania, Philadelphia, PA 19104-6018, USA and
Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802, USA

 

 

ABSTRACT:
Geographic variation in growth rates of the eastern fence lizard, Sceloporus undulatus, is extensive and has been interpreted in various ways. For example, slow growth rates of lizards in eastern woodland populations might reflect phenotypic plasticity induced by low food availability, unfavorable thermal environments, or a combination of both. By supplementally feeding free-ranging lizards from the New Jersey Pine Barrens, I tested the hypothesis that food directly limits growth rate. I also reared juveniles from New Jersey and from the Savannah River Site in South Carolina in a laboratory common garden" to test whether higher growth rates could be induced by ad libitum food, water, and unconstrained access to thermoregulatory sites, and whether there were population specific differences in responses to the common laboratory environment. Supplemental feeding had no significant effect on growth rates of free-ranging lizards relative to unsupplemented control lizards, and laboratory growth rates did not significantly exceed field growth rates for lizards in New Jersey or South Carolina. The absence of an increase in growth rates of supplementally fed, free-ranging or laboratory-reared lizards relative to control animals and population-specific allometry between snout-vent length and mass in a common laboratory environment is consistent with adaptive hypotheses that assume differences between populations in growth rate and other life history traits are the result of genetic differences. Implications for interpreting geographic variation in S. undulatus are discussed.

Key words: Growth rate; Sceloporus undulatus; Supplemental feeding; Geographic variation;

SREL Reprint#2043

Niewiarowski, P.H. 1995. Effects of supplemental feeding and thermal environment on growth rates of eastern fence lizards, Sceloporus undulatus. Herpetologica 51:487-496.

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