Estimating home range and temporal space use variability reveals age-related differences in risk exposure for reintroduced parrots

Abstract

Individual-level differences in animal spatial behaviour can lead to differential exposure to risk. We assessed the risk-exposure of a reintroduced population of k[a]k[a] (Nestor meridionalis) in a fenced reserve in New Zealand by GPS tracking 10 individuals and comparing the proportion of each individuals home range beyond the reserves fence in relation to age, sex, and fledging origin. To estimate dynamic space use, we used a sweeping window framework to estimate occurrence distributions from temporally overlapping snapshots. For each occurrence distribution, we calculated the proportion outside the reserves fence to assess temporal risk exposure, and the area, centroid and overlap to represent the behavioural pattern of space use. Home range area declined significantly and consistently with age, and the space use of juvenile k[a]k[a] was more dynamic, particularly in relation to positional changes of space use. The wider- ranging and more dynamic behaviour of younger k[a]k[a] resulted in consistently more time spent outside the reserve, which aligned with a higher number of incidental mortality observations. Quantifying both home range and dynamic space use is an effective approach to assess risk exposure, which can provide guidance for management interventions. We also emphasise the dynamic space use approach, which is flexible and can provide numerous insights towards a species spatial ecology.