Sealing the deal - Antarctic fur seals' active hunting tactics to capture small evasive prey revealed by miniature sonar tags.

The ability of predators to adopt hunting tactics that minimise escape reactions from prey is crucial for efficient foraging, and depends on detection capabilities and locomotor performances of both predators and prey. Here we investigated the efficiency of a small pinniped, the Antarctic fur seal (Arctocephalus gazella, AFS hereafter) at exploiting their small prey by describing for the first time their fine-scale predator-prey interactions. We compared them to those from another diving predator, the Southern elephant seal (Mirounga leonina) that forage on the same prey type. We used data recorded by a newly developed sonar tag that combines active acoustics with ultra-high resolution movement sensors to study simultaneously the fine-scale behaviour of both AFS and prey during predator-prey interactions in more than 1200 prey capture events for eight female AFS. Our results showed that AFS and their prey detect each other at the same time, i.e. 1-2 seconds before the strike, forcing AFS to display reactive fast-moving chases to capture their prey. In contrast, SES detect their prey up to 10 s before the strike, allowing them to approach their prey stealthily without triggering an escape reaction. The active hunting tactics used by AFS is likely very energy consuming compared to the stalking tactics used by SES but might be compensated by the consumption of faster-moving larger prey. We suggest that differences in manoeuvrability, locomotor performances and detection capacities and pace of life between AFS and elephant seals might explain their differences in hunting styles.