Underwater topography determines critical breeding habitat for humpback whales near Osa Peninsula, Costa Rica: implications for Marine Protected Areas

Abstract

Migrating humpback whales from northern and southern feeding grounds come to the tropical waters near Osa Peninsula, Pacific of Costa Rica, to reproduce and raise their calves. Planning effective marine protected areas that encompass humpback critical habitats require data about which oceanographic features influence distribution during the breeding period. This study examines the relationship between water depth and ocean floor slope with humpback whale distribution, based on sightings during two breeding seasons (2005 and 2006). Data are from the Southern and Northern subpopulations in the Eastern Tropical Pacific (ETP). Analysis followed the basic principles of the Ecological Niche Factors Analysis (ENFA), where indices of Marginality and Tolerance provide insights on the restrictiveness of habitat use. At a fine scale, physical factors such as water depth and slope define the critical breeding and nursing habitat for M. novaeangliae. Divergence in the subsamples means of depths and slope distribution, with the global mean of the study area in both eco-geographical variables, determine habitat requirements restricted by topographic features such as depths (< 100 m) and slope (< 10%), and locate the key breeding and nursing habitat of the species within the continental shelf domains.

Patterns of Spatial and Temporal Distribution of Humpback Whales at the Southern Limit of the Southeast Pacific Breeding Area

“…Spatially, the 98% of the sighted humpbacks were in the neritic zone (<200 m depth) which is similar to the sighting percentage reported in breeding areas elsewhere e.g., [19], [40]–[43]. The existence of a segregated pattern of distribution is a characteristic of breeding and calving regions and such pattern occurs regardless of the width, slope or the distance of the continental shelf break to the coast.…”

“…Although all individuals are present in neritic waters, mother and calf groups typically occupy shallower waters closer to shore, while groups composed of adult (e.g., competitive groups) and sub-adult individuals are widely distributed between shallow, moderate depths and the continental shelf break. This distributional pattern has been recorded in wintering areas of the Southeast Pacific population off the coast of Ecuador [5], [17] and Colombia [18], resembling the patterns observed in breeding regions elsewhere e.g., Costa Rica [19], [20], Hawaii [21], [22], Brazil [23], Madagascar [24] and eastern Australia [25]. However, the segregated pattern may not be evident in all wintering areas as it may depend on site-specific characteristics related to a suite of abiotic factors and the extent of human disturbance.…”

Identification of humpback whale breeding and calving habitat in the Great Barrier Reef

“…We selected 4 environmental variables -water depth, sea surface temperature (SST), distance from the coast and seafloor slope (measured in degrees) -based on their importance identified in previously published studies investigating relationships between humpback whale distribution and the environment (Ersts & Rosenbaum 2003, Johnston et al 2007, Rasmussen et al 2007, Oviedo & Solís 2008. Two additional environmental variables, distance to nearest reef and seafloor rugosity, were also investigated to assess whether these variables may contribute to humpback whale distribution and habitat preference in the GBR.…”

Analyses of least cost paths for determining effects of habitat types on landscape permeability: wolves in Poland

“…The global tolerance of the species (the inverse of the global specialization) indicates how specialized a species is, with values close to one for euryoecious (broad niche) and values close to zero for stenoecious (narrow niche) species. ENFA has been applied often with an explicit conservation aspect to a variety of species, ranging from corals to mammals (e.g., Bryan and Metaxas 2007; Oviedo and Solís 2008). The resulting habitat suitability map can, in turn, be used to determine costs (e.g., by inversing the values) and finally to conduct a least cost path analysis (Wang et al 2008).…”