DODD: ECOLOGY OF SANDHILLS POPULATION OF GASTROPHRYNE CAROLINENSIS 35


 Gray (1989) suggested that the mean body size of numerically dominant
species should be reduced during an environmental perturbation. G. carolinensis
is clearly the dominant species in the amphibian community at Breezeway Pond
(Dodd 1992). However, the mean body size (both SUL and weight) did not change
significantly during the study. In fact, the greatest weights occurred in 1990, the
year of the most severe drought effects, although the population size declined.
These results mirror those obtained for the striped newt at the same site (Dodd
1993). Hence, my data do not substantiate Gray's (1989) predictions.

 Longevity.-The oldest wild-caught G. carolinensis at Breezeway Pond were
at least in their fourth year, the same age that Fitch (1956) reported for G.
olivacea in Kansas. Eastern narrow-mouthed toads captured after four years were
probably in their first or second year when initially caught. Fitch (1956) suggested
that the plains narrow-mouthed toad might live a few years beyond four, and that
most of the breeding population consisted of 3-year olds. A similar scenario seems
reasonable for G. carolinensis at Breezeway Pond.

 Mortality.-Trap mortality resulted primarily from desiccation. G.
carolinensis seem particularly prone to desiccation despite attempts to minimize its
impact. Smaller animals are more susceptible than larger animals. Anderson
(1954) noted similar results and suggested that desiccation made the toads more
vulnerable to predation by the ant Iridomyrmex humilis. Such a hypothesis seems
reasonable inasmuch as dehydration reduces locomotor capacity in frogs (Moore
and Gatten 1989). Invertebrate predation undoubtedly occurs in the confines of a
bucket, but its effects are unknown in wild populations.


 Response to Drought


 Drought, especially long-term drought, may have serious consequences for
 amphibians that breed in isolated temporary ponds in sandhill habitats (Dodd
 1993). This is because most Nearctic amphibians, including Gastrophryne, usually
 lack special reproductive adaptations to resist or avoid drought conditions.
 Because they are bound to water, a severe reproductive cost will be realized when
 environmental conditions are not favorable for reproduction. Yet, drought occurs
 regularly in the southeastern United States and is quite common in the Upper
 Etonia Creek Basin that contains the Ordway Preserve (Motz et al. 1991).
 Dodd (1993) suggested that drought might have three effects on populations
 of striped newts, Notophthalmus perstriatus, sympatric with G. carolinensis in
 upland sandhill habitats. Localized newt populations might be extirpated, newts
 could move to other nearby breeding sites if available, or newts could outlast the
 drought in favorable refugia and take advantage of predator-free habitats once the