Terrestrial habitat use by pool -breeding amphibians in a suburban landscape

I studied terrestrial habitat use by spotted salamanders (Ambystoma maculatum), blue-spotted salamanders (A. laterale), wood frogs (Rana sylvatica), and eastern newts ( Notophthalmus viridescens) at two study sites containing three breeding pools. My research involved two large-scale studies of amphibian distribution and movement within terrestrial habitats, as well as three experimental studies.;In the movement studies, large blocks of terrestrial habitat were enclosed by pitfall traps and fencing so that distribution and movement patterns of resident amphibians could be studied. Terrestrial densities within 26 field enclosures located 0--300 m from breeding ponds were generally low (Range 0--6 individuals of each species/100 m2). At one site, at least 40% of wood frogs, 52% of blue-spotted salamanders, and 60% of spotted salamanders wintered >100 m from the breeding pond. Males tended to winter closer to the breeding pond than females, although this relationship was not statistically significant for all species in all years. Adult wood frogs and eastern newts were largely absent from upland forest habitat adjacent to the breeding ponds during spring and summer, but entered these areas in significant numbers in the fall to overwinter. Juvenile recruitment fluctuated dramatically across years, resulting in considerable variation in the numbers of juveniles moving through terrestrial habitats. These results suggest that effects of habitat loss on adult and juvenile distribution and mortality might vary considerably across years and across seasons. In addition, protection of narrow buffer strips around breeding ponds might be even less effective than was previously thought, due to the disproportionate representation of males within these areas.;I conducted field experiments involving (1) removal of small mammal burrows to determine if burrow availability influences salamander density, and (2) manipulation of spotted salamander densities to determine if increased density is associated with decreased growth, fecundity, condition, or probability of re-emerging to breed. Salamanders were over three times more likely to leave plots where mammal burrows were experimentally removed than they were control plots, prior to the summer inactive period. Spotted salamanders housed at high-density (15 individuals/enclosure) were less likely to re-emerge in subsequent years to breed than were salamanders housed at low density (5 individuals/enclosure). Results suggest that conspecific distribution and burrow availability might limit the density of spotted salamanders within terrestrial habitats.;I also investigated spotted salamander burrow occupancy patterns using laboratory and field experiments where salamanders were housed alone or in pairs, in arenas with either one or two burrows. In the single-burrow field experiment, mean burrow occupancy rate was 90% for individuals housed alone and decreased significantly (79%) when intruders and residents were housed together. Intruders were significantly less likely than residents to occupy burrows. However, spotted salamanders frequently co-occupied burrows (mean burrow co-occupancy rate = 59%). In the single-burrow laboratory experiment, mean burrow occupancy rate was >95%, both when salamanders were housed alone and in pairs. However, salamanders housed in pairs with two burrows co-occupied burrows less frequently than expected by chance, and greater size disparity was associated with lower burrow co-occupancy rates. Results suggest that spotted salamanders may often fail to effectively defend burrows and exclude conspecifics, although avoidance of occupied burrows could affect spacing in terrestrial habitats.