Seasonal foraging activity and microhabitat selection by echidnas (Tachyglossus aculeatus) on the New England Tablelands

Abstract

AbstractSeasonal foraging activity and microhabitat selection by echidnas on the New England Tablelands was determined by monitoring the number and relative predominance of different types of digging activity on a 2 km × 50 m transect over a 12 month period. Digging was classified into four basic types: those into the soil surface (SOILDIGS); those at the base of logs, stumps or trees (LOGDIGS); those at the base of termite mounds; and those in the litter. SOILDIGS were most prevalent, accounting for 490 (74%) of the total 666 digging records. The number of SOILDIGS correlated with season and temperature, reaching a maximum of 11 ha−1 per month in late spring and a minimum of zero in winter. SOILDIGS were attributed to searches for ants and scarab beetle larvae. Approximately half of the SOILDIGS exposed ant nests or galleries, while the remainder were presumed to result from searches for the larvae of pasture dwelling scarab beetles, particularly Sericesthis spp. Scarab beetle larvae were absent from echidna scats collected during winter but occurred in 20% of scats collected during summer, LOGDIGS accounted for 157 digging records (24%) and were attributed to searches for ants and termites, LOGDIGS did not vary with season or climate, but the proportion of LOGDIGS that exposed ant or termite nests or galleries changed from 48% in winter to 5% in summer. The distribution and density of SOILDIGS and LOGDIGS along the transect correlated significantly with the availability of echidna shelter (or refuge) sites, in all seasons Some residual variation in digging activity was explained by the number and biomass of ants active on the soil surface, but not with any other direct or indirect measures of food availability. Seasonal changes in foraging activity by echidnas, and their apparent dependence on shelters, are interpreted in an energetic context as strategies for reducing predation and overcoming a period of increased energy demand and decreased food availability experienced during winter.