A drone-based Antarctic fur seal (Arctocephalus gazella) census of the St. Telmo Islands, South Shetland Archipelago

Accurate census counts are fundamental to population management, but can be challenging to obtain in remote polar environments. The standard approach for income breeding pinnipeds, such as the Antarctic fur seal (Arctocephalus gazella), is to annually survey pup production. Fur seal population dynamics in the South Shetland archipelago are largely driven by two breeding colonies, Cape Shirreff and the Saint Telmo Islands. Although annual counts have been undertaken at Cape Shirreff since the 1990’s, logistical challenges have prevented surveys of the St Telmo Islands since 2008. Over the last decade unmanned aerial systems (UAS), or drones, have become indispensable tools for wildlife monitoring. We used a medium-range vertical takeoff and landing (VTOL) UAS to obtain pup counts from the St Telmo Islands during the 2018-19 field season. The APH-28 provided a minimally-invasive, robust, and accurate (error rates <2%) survey tool. The corrected 2019 census count from the St Telmo Islands was 333, which represents a 79% reduction since the most recent survey in 2008, and a 90% reduction from the peak of recent production in 1997. Given the historical importance of Cape Shirreff and St Telmo to the AFS population dynamics in the South Shetlands archipelago, these declines emphasize the need to synoptically survey all known and potential breeding sites across the South Shetland Islands as soon as is practicable.