Habitat use by South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) in a marine protected area in southern Brazil

We present an analysis of the influence of relief on habitat use by South American fur seals (Arctocephalus australis) and sea lions (Otaria flavescens) in the Wildlife Refuge of Ilha dos Lobos (WRIL) in southern Brazil. To test the hypothesis that the spatial occupation of WRIL by these two species of South American pinnipeds is related to the higher relief found in the northern region of the island, we generated a digital three-dimensional model of Ilha dos Lobos. This model was based on photogrammetry of 157 aerial images obtained from an unmanned aerial vehicle (UAV) in 2019. Aerial censuses were conducted between 2010 and 2020 using a helicopter and a UAV to assess the abundance of pinnipeds. The effects of altitude and seasonality on species abundances were assessed using Generalized Linear Mixed Models with Negative Binomial error distribution. The results indicated the existence of variation in the relief of the island, with higher areas in the northern region highly correlated with higher densities of both South American pinniped species on the island. The relationship between pinniped density and altimetry was statistically significant, indicating that these animals preferred to use the higher areas of the island when resting. These results suggest the importance of UAV operations and employment for understanding habitat use by fauna in protected areas.