Modeling breeding habitats of humpback whales Megaptera novaeangliae as a function of group composition

Abstract

Humpback whales Megaptera novaeangliae are undergoing a population increase after ca. 40 yr of a whaling ban. However, anthropogenic activities threaten their recovery in recolonized breeding habitats. Predictive habitat models are important tools that can help create effective conservation measures. Due to the spatially structured distribution of this species that depends on the presence of calves and the number of individuals, models must account for specific population variability that could refine management direction. We modeled potential breeding habitats of humpback whales considering group type variability. A total of 10 yr of data (3115 sighted humpback whales from 2010 to 2019) obtained from whale-watching surveys in the breeding area of northern Peru (4°S, Southeast Tropical Pacific) were used. Maximum entropy models were constructed to predict potential habitats for breeding humpback whales considering groups with and without calves. Depth and sea surface temperature were used as descriptors for modeling the potential habitat of humpback whale groups. Depth was the main explanatory variable for all models. The optimal potential habitat for groups with calves was located between 20 and 50 m depth. Groups without calves ranged more widely in habitat, from 20 to 100 m depth. The predictive character of these models shows segregated potential habitats of breeding humpback whales, which could help refine conservation actions. For example, limiting the number of whale-watching boats in nearshore waters when mother and calf pairs are present would reduce conflict, while restricting the use of gillnets in transitional neritic to oceanic waters is mandatory to mitigate entanglements.

Topics & Concepts