Quantifying the behavioural ecology of fear: understanding the role of habitat fragmentation on predation pressure and prey behaviour via the automated monitoring of a sentinel species (#128)
The impacts of predators on prey are profound, with the so-called 'ecology of fear' impacting behaviour as diverse as foraging through to reproduction, ultimately impacting regional biodiversity. Despite this, research on the relative impacts of different types of predator in the same system remain poorly known, largely due to the logistical challenges involved in monitoring multiple species. We overcame this challenge by utilising the presence of a naturally occurring sentinel, the Noisy Miner (Manorina melanocephala), a bird that produces frequent alarm calls that are highly referential: different alarm signals are given in the presence of either a ground-based predator, such as a canid or snake, versus avian predators such as raptors. We therefore quantified the production of these calls as a reliable proxy of when, where and which type of predators were encountered in habitat patches of different sizes and at the centre versus the edge of patches over two-week periods during each season, surveying an hour either side of dawn, midday and dusk each day. Noisy Miners encountered ground-based predators at higher rates on the edge of fragments as opposed to their centre, with smaller fragments (<200m across) being exposed to greater predation pressure. In contrast, aerial predators were more commonly encountered by miners at the centre of patches, with patch size being relatively unimportant, reflecting differences in both the mobility and hunting behaviour of these different predator types. Together, these results highlight the complex nature of predation risk and how this varies with habitat structure, particularly given group predators primarily target young birds, whilst aerial predators take miners of all ages. When compared with key behavioural investment strategies utilised by resident miners, such as home range location within patches, body condition and subsequent stress levels, the broad-scale impacts of an ecology of fear can be elucidated.