High mortality rates in a juvenile free-ranging marine predator and links to dive and forage ability

1. High juvenile mortality rates are typical of many long-lived marine vertebrate predators. Insufficient development in dive and forage ability are considered key drivers of this. However, direct links to survival outcome are sparse, particularly in free-ranging marine animals that may not return to land.

2. In this study, we conduct exploratory investigations toward early mortality in juvenile southern elephant seals Mirounga leonina. 20 post-weaning pups were equipped with (1) a new generation satellite relay data tag, capable of remotely transmitting fine-scale behavioural movements from accelerometers, and (2) a location transmitting only tag (so that mortality events could be distinguished from device failures). Individuals were followed during their first trip at sea (until mortality or return to land). Two analyses were conducted. First, the behavioural movements and encountered environmental conditions of non-surviving pups were individually compared to temporally concurrent...