Where do sea lions live? Interspecific interactions and abiotic factors predict Steller sea lion habitat.

Abstract

Habitat selection by species is dependent on both abiotic factors and species interaction. With regards to species interaction, competition and facilitation can play a critical role regarding how a species selects its habitat. Previous work has suggested that Steller sea lions (Eumetopias jubatus) have been displaced from their haulout sites due to competition with California sea lions (Zalophus californianus). The purpose of our study is to understand what factors determine the number of Steller sea lion present at a haul out site in the Barkley Sound area in Bamfield, BC. We tested this by asking if the number of Steller sea lions at a haulout site at a certain time is related to the presence of California sea lions (as a proxy for interspecific interaction), time of day, and tide height or a combination of two or three of these variables. After running a generalized mixed effect model and competing our models using Akaike Information Criteria, our results indicated that tide height was the best predictor for explaining the number of Steller sea lions present at a haulout site. However, our results also indicated that the presence of California sea lions and time of day may play a role in determining Steller sea lion haulout sites as well. We found from this study that both species interaction and abiotic factors need to be collectively considered when predicting the mechanisms underlying species habitat choice in marine ecosystems.