Density-dependent changes in the distribution of Southern Right Whales (Eubalaena australis) in the breeding ground Peninsula Valdés

CRESPO, ENRIQUE ALBERTO; ARIAS, MAGDALENA; SUEYRO, NICOLAS; COSCARELLA, MARIANO ALBERTO

PeerJ

PeerJ Inc.

Año: 2018 vol. 6 p. 1 - 13

Background: The Southern Right Whale (Eubalaena australis) population of the South?western Atlantic Ocean is recovering. In the breeding ground of Peninsula Valdés, as a consequence of the population growth, expansion to new areas by some types of groups and a change in the habitat use patterns at the coastal area were recorded. Methods: We analysed information gathered from aerial surveys conducted along the coast of Peninsula Valdés in 15 years of effective sampling in a 19-year span. These surveys were divided into four periods (1999?2000; 2004?2007; 2008?2012 and 2013?2016) and estimated the density of whales in a 620 km of coast divided into segments of five km. Results: The density of the whales increased to near three whales per km2 (averaged over each period) in the high-density areas. When this mean number was reached, the significant changes in density in the adjacent areas were detected in the following period. These changes were a decrease in density in the high-density areas and an increase of density in the low-density areas. Discussion: We propose that a threshold in density elicits a response in habitat use, with the Mother-calf pairs remaining in the area, while the other groups are displaced to new areas.