Roost site selection and roosting behaviour in lesser short‐tailed bats (Mystacina tuberculata) in comparison with long‐tailed bats (Chalinolobus tuberculatus) in Nothofagus forest, Fiordland

Abstract

I studied the roosting ecology of the lesser short‐tailed bat (Mystacina tuberculata) during the summer months of 1997–2000 in lowland Nothofagus rainforest, Fiordland, New Zealand. Structural characteristics of communal day‐roost trees and cavities were compared with those of randomly available trees and cavities, and those used by a sympatric population of long‐tailed bats (Chalinolobus tuberculatus). I radio‐tracked 29 M. tuberculata to 20 communal roost cavities located in 16 trees. Twelve of 21 characteristics measured differed significantly between roost and random sites. M. tuberculata selected roosts in more open parts of the forest, in some of the largest red beech (Nothofagus fusca) trees and cavities available. Characteristics of trees used by the two bat species were similar. Both species roosted in large diameter, old age red beech. However, 11 of the 12 roost cavity characteristics varied significantly between bat species. Roost cavities used by M. tuberculata were significantly lower to the ground, had more entrances, and had larger entrance and internal dimensions than C. tuberculatus roosts. Nevertheless, roosts of both species were well insulated and exhibited stable internal temperatures. M. tuberculata roosting groups were dominated by females and young, and group size averaged 310 ± 88.1 bats (n = 40). Roosts were occupied for an average of 5.6 ± 6.9 days (n = 23). Group size was significantly larger than in C. tuberculatus, and roost residency time significantly longer. Differences in roost use and roosting behaviour between the two species should be considered when undertaking conservation management actions such as identifying trees for retention through logging cycles, or designating reserves.