Random exploratory behaviour by individual island colonists

The post-arrival behaviour of individuals in novel environments influences survival and population establishment. For pest species early detection and elimination of new arrivals is vital to prevent invasion, and this requires a thorough understanding of movement patterns post-arrival. Studies have previously investigated exploratory movements in novel laboratory environments, but not during colonization of natural systems. We individually released five adult male brown rats (Rattus norvegicus) onto a rat-free island and monitored their movements hourly for three weeks. We demonstrate that (i) in the period immediately following arrival individual movements are apparently random; (ii) individuals effectively remain around their release site for three days before dispersing further; (iii) range size is much larger compared to individuals at high-density; (iv) exploration rate is mediated by central place foraging behaviour. These low-density movement behaviours have implications for understanding animal colonization dynamics, and intercepting wide-ranging individuals of invasive species as they arrive at new locations.