[MARMAM] ABSTRACT: Multilevel Societies of Female Sperm Whales (Physeter macrocephalus) in the Atlantic and Pacific: Why Are They So Different?

[Hal Whitehead]

Just published in the International Journal of Primatology:

Multilevel Societies of Female Sperm Whales (Physeter macrocephalus)  
in the Atlantic and Pacific: Why Are They So Different?

Hal Whitehead, Ricardo Antunes, Shane Gero, Sarah N. P. Wong, Daniel  
Engelhaupt & Luke Rendell. 2012.  Int. J. Primatol.

Abstract:

We can examine the evolution of multilevel societies using comparative  
studies. Intraspecific comparisons are valuable because confounding  
factors are reduced. Female sperm whales live in multilevel societies.  
However, studies at several locations have found substantial and  
consistent differences in social structure between the eastern Pacific  
and North Atlantic Oceans, even though nuclear DNA shows no  
significant differentiation between the populations. In the Pacific,  
female sperm whales live in nearly permanent social units that  
typically contain about 11 females and immatures of multiple unrelated  
matrilines. These units form temporary groups with other units for  
periods of days, apparently exclusively with other units from the same  
cultural clan. Clans contain thousands of females, are not distinct in  
nuclear DNA, but are sympatric and have distinctive culturally  
determined vocalizations and movement patterns. In the North Atlantic  
social units rarely group with other units, and there is no evidence  
for sympatric cultural clans. Possible drivers of these contrasts  
include oceanographic differences, predation, the effects of whaling,  
and culture. We suggest that protection against predation by killer  
whales is the primary reason for grouping in the Pacific, and as  
killer whales do not seem such a threat in the Atlantic, social units  
there rarely form groups, and have not evolved the clans that  
primarily function to structure interunit interactions. This analysis  
highlighted several factors that may influence the evolution of  
multilevel societies, ranging from the attributes of resources, to   
predation, anthropogenic effects, culture, and even the cultures of  
other species.

Available at: http://whitelab.biology.dal.ca/labpub.htm

Hal Whitehead, Dalhousie University: hwhitehe at dal.ca