Tracking top predators in the South Atlantic

By Dr Alastair Baylis who was in the Falklands in February and March 2013

Marine mammals (e.g. cetaceans and pinnipeds) are top predators in the world’s oceans. They can have important effects on ecosystem structure and function, and serve as indicators of ecosystem health. Several marine mammal species breed at the Falkland Islands. However of particular concern is a precipitous decline in the number of southern sea lions (Otaria flavescens) - now the focus of multi-year study. In the 1930's the Falkland Islands was home to the largest population of southern sea lions in the world (pup production estimated to be 80,000). Between the 1930’s and 1990’s the population declined by 97% (reasons unknown). Today pup production is estimated to be less than 2,800. Despite this dramatic decline and failure to recover, surprisingly little is known about the foraging ecology of sea lions at the Falkland Islands - information that is vital in order to identify any potential impediments to population recovery.


Eager to redress knowledge gaps, a team of pinniped biologists lead by Dr Iain Staniland (BAS) and Dr Alastair Baylis (Deakin University, previously FC) successfully deployed 26 satellite tags on southern sea lions in 2011 and 2012. In 2013, working in collaboration with SAERI and FC, the team returned to the Falklands in order to deploy GPS units and dive loggers. These sophisticated devices collect fine scale location data and dive data - needed to better assess important at-sea areas for sea lions. With the help of Rachael Orben (UCSC Costa Lab) and Dr John Arnould (Deakin University) GPS units were successfully deployed and recovered (a first for Falklands sea lions), while valuable diet and genetic samples were also collected. In total 37 sea lions have now been tracked (adults and juveniles), and some initial results are presented in the figure below. The ambitious team is already planning the next season and hope to profile the foraging location and diet of sea lions from the largest breeding colonies on both East and West Falklands.
The research was generously supported by the Shackleton Scholarship Fund and a JNCC small projects grant, received through the Falkland Islands Government Environmental Planning Department. We extend our sincere thanks to SAERI, FIG EPD and FC for their invaluable support.



Photographed by Rachael Orben