Temporal and geographic variation in the social structure of female sperm whales

Abstract

The social structure of female sperm whales (Physeter macrocephalus) was examined from data collected during studies of identified individuals off the Galápagos Islands in 1985, 1987, and 1989, off the Seychelles Islands in 1990, and off mainland Ecuador in 1991. Three levels of social organization were examined in the Galápagos Islands studies. "Units," permanent associations between individuals, showed no significant deviation from a mean size of 13 individuals. "Groups," temporary associations between units lasting a few days, had a mean size of 24 individuals. Group size was lower in 1987 (an "El Niño" year) than in 1985 or 1989, but this difference was not statistically significant. "Aggregations" of groups in the same general area lasting periods of hours were significantly larger in 1985 (mean of 77 individuals) than in 1987 (mean of 47 individuals). There are significant differences between areas in aggregation sizes but not in group sizes. Groups appear to aggregate frequently off the Galápagos Islands, occasionally off mainland Ecuador, and very rarely off the Seychelles Islands. These temporal and geographic differences in sizes of groups and aggregations in sperm whales are probably caused by variations in the distribution and abundance of their food, but responses to recent exploitation may also be a factor.

Diving behavior of sperm whales in relation to behavior of a major prey species, the jumbo squid, in the Gulf of California, Mexico

“…During the study, sperm whales were abundant around Isla Tortuga, and the average search time for sperm whales (57 min) was much shorter (by 86 to 98%) than that reported for other areas (Whitehead & Kahn 1992, Jaquet & Gendron 2002. During 6 days at sea, we identified 74 individual sperm whales in an area of less than 70 km 2 , confirming their high abundance in the study area and during the study period.…”

Communication and Acoustic Behavior of Dolphins and Whales

“…Yet animals within these killer whale and sperm whale groups frequently disperse kilometers away from one another, and may be out of sight for hours. Two groups may meet and intermingle for hours to days (Whitehead and Kahn 1992), but then resegregate into the original groups. Both killer and sperm whales have group distinctive vocal repertoires that are thought to function "to maintain the integrity of the pod" (Ford 1989;Weilgart and Whitehead 1997).…”

Population genetics and social organization of the sperm whale (Physeter macrocephalus) in the Azores inferred by microsatellite analyses

“…The sperm whale (Physeter macrocephalus L., 1758) presents a highly complex social structure (Whitehead and Kahn 1992), which includes both stable groups tied with social bonds as well as temporary aggregations of such groups with possibly unrelated individuals (Lettevall et al 2002). The most common social group is the socalled "primary" social group, which is composed of adult females, sub-adults, and calves of both sexes.…”

“…Few studies based on microsatellites were dedicated to the sperm whale (Richard et al 1996a,b, Bond 1999, Lyrholm et al 1999. The social structure of groups of females and immature individuals has been studied in Sri Lanka (Gordon 1987), off mainland Ecuador (Whitehead and Kahn 1992), in the southeast Caribbean (Gordon et al 1998) and off the coast of northern Chile (Coakes and Whitehead 2004), but none of these studies used genetics as a tool to analyse relatedness and relationships between individuals and social groups.…”