Communal nesting in the usually solitary marsupial, <i>Phascogale tapoatafa</i>

Abstract

Abstract The marsupial brushtailed phascogale Phascogale tapoatafa is a solitary, hollow‐dependent, arboreal insectivore that occurs at low densities in open forests and woodlands of Australia. Data gathered from nest box surveys (4 years), and from radio‐tracking phascogales to nest sites (3 years) in south‐western Australia confirm solitary nesting after dispersal. However, in the winter of a single year, nest box surveys in one study area showed that 56% of individuals were nest sharing. On a neighbouring site, 81 group nests were also recorded among 18 radio‐collared individuals. In both areas, groups comprised two to four individuals of any age/sex combination. The same phascogales tended to nest together and in a number of different sites. Nest sharing between females was restricted to territory boundaries and continued after the annual die‐off of the males. Nest sharing coincided with prolonged drought conditions and in this year mature phascogales were significantly smaller than normal, i.e. males 25% less in weight, females 12% less. Communal nesting seemed to be a response to thermoregulatory difficulties posed by the three interrelated factors of low body mass, declining temperatures and declining food availability. Nest sharing in this species appeared to be a behavioural indicator of an energetics crisis, there was a population decline during the drought period and a population crash in the following year.