Assessing quality of clearcut habitats for amphibians: Effects on abundances versus vital rates in the southern toad (Bufo terrestris)
Brian D. Todd*, Betsie B. Rothermel
The University of Georgia, Savannah River Ecology Laboratory, Drawer E,
Aiken, SC 29802, USA
Abstract
Forest clearcutting is a form of habitat alteration that drastically alters
the landscape and
may contribute to declines in amphibian populations. Indeed, many studies
have documented decreases in amphibian abundances and species richness
in clearcuts. The development of effective conservation strategies to
reduce the effects of timber harvesting has been hindered by lack of knowledge
of the mechanisms underlying these changes in abundance. To better understand
the potentially negative consequences of forest clearcutting, we used
field enclosures in forested and clearcut habitats to examine changes
in the survival and growth of juvenile southern toads (Bufo terrestris)
over a two-month period. We also conducted a comparative monitoring study
using drift fences and pitfall traps in forests and clearcuts to determine
the effect of clearcutting on the abundance of juvenile southern toads.
We found no significant effect of habitat on the number of juvenile southern
toads captured in forests or clearcuts. In contrast, the average survival
of toads in clearcut enclosures was significantly reduced compared to
that of toads in forested enclosures (17 ± 5% versus 61 ±
3%). Toads surviving in clearcuts were also significantly smaller than
those surviving in forested enclosures (27.9 ± 0.1 mmversus 30.3
± 0.8 mmSVL). Our results highlight the difficulty in interpreting
abundance patterns as a sole metric for habitat comparison. Because there
is much interest in studying the effects of habitat alteration on amphibian
populations, we recommend that future studies place more emphasis on determining
changes in vital rates of populations following habitat alteration.
Keywords: Amphibians, Demographic rates, Forest management, Population monitoring, Survival
* Corresponding
author: Tel.: +1 803 725 0422; fax: +1 803 725 3309.
E-mail addresses:
todd@srel.edu (B.D. Todd), rothermel@srel.edu (B.B. Rothermel).
SREL Reprint #3005
Todd, B. D. and B. B. Rothermel. 2006. Assessing quality of clearcut habitats for amphibians: Effects on abundances versus vital rates in the southern toad (Bufo terrestris). Biological Conservation 133:178-185.
