Habitat preference reflects social organization of humpback whales (Megaptera novaeangliae) on a wintering ground

Abstract

Habitat preference is driven by a complex interaction among behavioural patterns, biological requirements, and environmental conditions. These variables are difficult to determine for any species but are further complicated for migratory marine mammals, such as humpback whales Megaptera novaeangliae. Patterns of habitat use in relation to social organization potentially exist for this species on their wintering grounds. Using an integrated GIS approach, we examined the degree to which spatial patterns of habitat stratification are correlated within different humpback whale group types from 6 years of sighting data (1996)(1997)(1998)(1999)(2000)(2001) collected on the Antongil Bay, Madagascar, wintering ground. Stratification of humpback whale sightings by behavioural classification showed significant variation in depth and distance from shore. Distribution by depth could not be described as a function of group size but could be described as a function of social organization, with mother-calf pairs showing a strong preference for shallower water compared to all other group types. Group size and social organization seem to be factors in distribution by distance from shore. Significant diurnal patterns in distribution by depth and distance from shore also exist, where mother-calf groups maintain a relatively stable distribution and pairs and competitive groups are the most variable. Patterns of habitat preference on this wintering ground appear to be guided by social organization, where distribution by depth and distance from shore highlight areas critical to conservation.

Summer distribution patterns of southern resident killer whales Orcinus orca: core areas and spatial segregation of social groups

“…Currently we have insufficient information to compare diets of different SRKW pod groups, but this may be an important consideration in understanding pod-specific distribution patterns. Social groups of other cetacean populations are also known to segregate space use, which has been linked to differential foraging success or reproductive status (Ersts & Rosenbaum 2003, Whitehead & Rendell 2004. While associations to foraging and reproduction cannot be made here, these remain important potential implications of pod-specific space use.…”

“…Whitehead 1997). For example, habitat preferences of the humpback whale Megaptera novaeangliae on a wintering ground are influenced by social structure in that mother-calf groups prefer consistent habitat types while paired adults or competitive groups have variable preferences (Ersts & Rosenbaum 2003). Different uses of space among cetacean social units can result from unique responses to physical habitat characteristics, anthropogenic and naturally occurring risk factors, and other conditions driving animal distribution.…”

Spatial linkages between coral proxies of terrestrial runoff across a large embayment in Madagascar

“…1) covering an area of 2800 km 2 , with a mean depth of 41.5 m and a coastline of 270 km extending 80 km inland (Ersts and Rosenbaum, 2003). Almost all populated areas are located in the northern and western coastal regions of the bay, including the largest urban areas of Maroantsetra and Mana- nara.…”

Behavior of humpback whales, Megaptera novaeangliae (Cetacea: Balaenopteridae): comparisons between two coastal areas of Brazil

“…Competitive groups were more often far from the coast as compared to mother+calf,and one escort and dyads (ERSTS & ROSENBAUM 2003).…”