Influence of abundance of small-mammal burrows and conspecifics on the density and distribution of spotted salamanders (Ambystoma maculatum) in terrestrial habitats

Abstract

Spotted salamander (Ambystoma maculatum) distributions were studied within eighteen 272-m2 field enclosures in upland deciduous forest adjacent to two breeding ponds. The enclosures were subsequently used in experiments involving (i) removal of small-mammal burrows to determine if burrow abundance influenced salamander density and (ii) manipulation of salamander densities to determine if increased density was associated with decreased growth, fecundity, or probability of re-emerging to breed. Mean density of salamanders wintering in enclosures <65 m from the breeding ponds was 1.0/100 m2 (SD = 1.1/100 m2, n = 17, range = 0–4.0/100 m2). Density declined as distance to the nearest breeding pond increased, and the sex ratio was skewed sharply toward males (8:1) wintering close (<65 m) to the pond but not farther from the pond (1:1). Males residing within the enclosures weighed more than males wintering farther from the breeding ponds. Migrating salamanders were over 3 times more likely to leave burrow-removal plots than control plots prior to the summer inactive period. Salamanders housed at high density (15/enclosure) were less likely to re-emerge to breed than were salamanders housed at low density (5/enclosure), but we observed no effects on growth or fecundity. Results suggest that conspecific distribution and burrow availability might affect the density of spotted salamanders within terrestrial habitats.