High-Resolution SAR-Based Monitoring of Southern Elephant Seals: A Case Study at St Andrews Bay

Abstract

In this study, we investigate the potential of high-resolution satellite-based Synthetic Aperture Radar (SAR) imagery acquired by the German radar mission TerraSAR-X for detecting southern elephant seals (Mirounga leonina) in polar environments. The monitoring of seal populations is crucial because they serve as indicators of ecosystem health and can reveal behavioural and population changes. However, traditional field-based surveys are logistically challenging, weather-dependent, and temporally limited. Spaceborne SAR imagery offers a weather-independent and daylight-independent alternative with high spatial resolution and consistent revisit times. We analyse TerraSAR-X Spotlight SAR scenes of a southern elephant seal breeding colony at St Andrews Bay (South Georgia) during and immediately after the peak breeding season. TerraSAR-X acquisitions in Spotlight mode provide a spatial resolution of approximately 25 cm, enabling the potential identification of individual animals. We investigate the radar backscatter characteristics of the seals and compare them to surrounding beach sediments. To the best of our knowledge, no prior studies have systematically analysed seal backscatter properties. Our work addresses this gap by concentrating on a single species within a defined colony.