Spatial Differentiation Among Family Members of the Cooperatively Breeding Giant Babax Dynamically Adjusts to...

In cooperatively breeding systems, spatial use and its associated resource acquirement pattern underlies parenting behavior of different group members. Therefore, quantifying spatial differentiation among group members is helpful to understand how parental care and cooperative breeding strategies evolve. In the giant babax (Babax waddelli), we used GPS tracking to quantify home range sizes and movement behaviors of dominant breeders and helpers, aiming to examine whether spatial differentiation occurred during different annual cycle phases. During the breeding phase when parental care is essential for offspring, helpers occupied larger home ranges and tended to move within higher-altitude habitats than did dominant breeders. However, the temporal variation in movement patterns exhibited no significant difference between dominant breeders and helpers. During the postfledging phase when offspring require less parental care, helpers continued to occupy larger home ranges and move within higher-altitude habitats; and the movement effort of dominant females was complemented by that of dominant males and helpers. During the wintering phase when offspring did not require parental care anymore, helpers were more likely to move in lower-altitude habitats than dominant breeders, and no significant differences in the movement pattern were observed between dominant breeders and helpers. These findings provided evidence that spatial differentiation among family members of the giant babax dynamically adjusts in response to temporal fluctuations in offspring demand for parental care. Therefore, spatial differentiation may serve as the underlying mechanism for the diversification of parental care strategies within cooperatively breeding systems.