Monitoring beluga whales from space: estimating abundance and evaluating social structure using VHR satellite imagery

Improving monitoring efforts of Arctic species is becoming increasingly important given the rate of change in Arctic marine ecosystems and the presumed impact on Arctic marine mammals, such as beluga whales (Delphinapterus leucas). Very High Resolution (VHR) satellite imagery is emerging as a promising tool for efficiently monitoring beluga whale populations, which can be logistically challenging with current methods. Here we use VHR satellite imagery to investigate two conservation relevant aspects of beluga whale populations: abundance and social dynamics. First we determined two missing pieces of information required to estimate beluga whale abundance in VHR satellite imagery: 1) depths that beluga whales are visible in VHR satellite images, which are used to define availability bias correction factors, and 2) a comparison of abundance estimates in VHR satellite imagery to current aerial methods. We determined that beluga whales can be detected only at the surface in turbid water and at depths of 0 – 2 m in clear water in 0.31 m resolution VHR imagery, and that beluga whale availability bias corrected abundance estimates made from synchronous VHR satellite imagery and drone surveys were comparable. We further used VHR imagery to describe beluga whale group size, composition, and cohesion in beluga whale populations from Cumberland Sound, Eastern High Arctic – Baffin Bay, and Western Hudson Bay in relation to anthropogenic disturbance, density, and social context. We found that group size decreased with harvest, which seemingly reflects population decline or removal of key social individuals, while recent increases in vessel traffic were associated with larger group sizes and greater spatial cohesion, possibly suggesting an adaptative response to increase vigilance to vessel disturbance. Beluga whale social cohesion was mainly influenced by the presence of juvenile whales, with adult-juvenile mixed groups having smaller inter-individual distances than groups with