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Desiccation and Shelter-Site Use in a Tropical Amphibian: Comparing Toads with Physical Models

L. Schwarzkopf and R. A. Alford
Functional Ecology
Vol. 10, No. 2 (Apr., 1996), pp. 193-200
DOI: 10.2307/2389843
Stable URL: http://www.jstor.org/stable/2389843
Page Count: 8
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Desiccation and Shelter-Site Use in a Tropical Amphibian: Comparing Toads with Physical Models
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Abstract

1. Shelter-site selection is a critical component of the behaviour of most mobile organisms, allowing them to avoid adverse physical and biotic environmental conditions. This paper examines the patterns of diurnal retreat-site use of tropical cane toads (Bufo marinus), with respect to the ability of various shelter-site types to protect against desiccation. 2. To measure desiccation rates in different shelter-site types, agar models the size and shape of an adult toad were placed in sites used by toads and allowed to desiccate. Models were put in burrows, in tall grass either close to (<1 m, `wet grass' sites) or far from (>10 m, `dry grass' sites) permanent water, and in the open on sandy ground (`control' sites). These measurements were carried out during dry, wet, and moderately wet seasonal conditions. 3. Desiccation rates of models varied dramatically among seasons. During the wet season, only models located in burrows lost any mass; models in other locations gained mass. During the dry season, all models lost mass, but rates of loss were lowest in burrows and `wet grass' sites. During the late wet season, all models lost mass at lower rates than in the dry season; models in control sites lost water at the highest rates, whereas models in `wet grass' sites, `dry grass' sites and burrows all lost water more slowly. 4. During each season, we radio-tracked individual toads and recorded the characteristics of shelter sites they used. In each season, the sites most often used were those which provided the most protection from desiccation. Toads used burrows most frequently in the dry season, `dry grass' sites in the wet season, and showed no preference for any shelter-site type during the late wet season. This suggests that toads select shelter sites based on their ability to reduce rates of water loss. 5. In the dry season, toads were more likely to return to burrows than to other shelter-site types. This may occur if burrows are scarce resources that are relatively difficult to find, and/or if burrows are enhanced by individuals, making it worthwhile to return to them. In addition, burrows may provide protection from predation as well as desiccation.

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