The first response of many animals to altered environmental conditions is via behavioural adjustments. Habitat loss and fragmentation represent major alterations to natural environments and are key contributors to the global biodiversity crisis. This chapter illustrates how animal behaviour can be modified in response to habitat loss and fragmentation, the implications of these changes for individual fitness, and how behavioural responses can vary both within and among species. It then describes the consequences of changes in behaviour for populations, communities, and ecosystems. Lastly, it focuses on outlining how the impacts of habitat loss and fragmentation on animals can be mitigated in the context of animal behaviour, and proposes knowledge gaps and research priorities for behavioural ecologists and environmental managers.