Aggregation and site tenacity under downed logs in Salamandrella keyserlingii (Caudata: Hynobiidae)

Abstract

Darhadyn Wetland, Mongolia, is located in a subarctic steppe–tundra climate, where salamanders are exposed to both extremely hot and cold environments. We hypothesized that log refugia provide an adaptive advantage to salamanders in these environments because the habitat availability hypothesis predicts that restricted habitat availability can cause aggregation that plays a role in the initial stages of the evolution of complex sociality. To test this hypothesis, we assessed whether a rare salamander species aggregated under a limited shelter resource. Many small vertebrates use terrestrial burrow refuges. While many salamander species also use burrows, Salamandrella keyserlingii at Darhadyn used only downed log refuges (i.e., restricted habitat availability). Some individuals displayed site tenacity to remain under a specific log, and one or more of the same individuals were located continually or frequently under the same logs. The majority of recapture events (96.8 %, 121/125) did not show any movements of salamanders between logs. Of the 300 capture events, 66 % were aggregating. The maximum number of individuals sharing a log refuge on the same day (i.e., sharing group size) ranged from 2 to 9. Individuals were resident nonrandomly in downed log refuges, i.e., an aggregation pattern was nonrandom. Based on these findings, we provided conservation measures such that total number of individuals captured per log over the course of the study (maximum number = 32) had a positive relationship to 1 of 7 explanatory variables (i.e., log decaying class in ascending order). Thus, the retention of decaying downed logs is important for the conservation of this species.