Abstract: Social org of Humpbacks

Michael Williamson (whe_william@flo.org)
Mon, 10 Dec 1994 14:18:47

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From: Michael Williamson <WHE_WILLIAM@flo.org>
Subject: Abstract: Social org of Humpbacks
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From:         "Phillip J Clapham (Genetics)"
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  Clapham, P.J.  1993.  Social organization of humpback whales on a North
Atlantic feeding ground.  Symp. Zool. Soc. Lond. 66: 131-145.
  Data from a long-term study of individually identified humpback whales,
Megaptera novaeangliae, were used to describe patterns of association and
grouping of this species on one of its principal North Atlantic feeding
grounds in the southern Gulf of Maine.  Most groups were small and
unstable, and individual whales of both sexes and all age classes
associated with many conspecifics.  Only six instances of stable
associations were recorded.  Analysis of the class composition of
singletons and pairs showed that: 1) among singletons, juveniles of both
sexes were significantly overrepresented, and mature females
significantly underrepresented; 2) male-female adult pairs were
overrepresented; 3) adult-juvenile pairs of any gender combination were
underrepresented; and 4) pairings between adult males were
underrepresented except during feeding.  Only 12 of 2690 pairs consisted
of animals who were known to be related.  It is suggested that the
fission-fusion sociality that characterized the study population
represents a response to two ecological factors.  Firstly, absence of
predation nullifies the need for large groups for predator detection or
communal defence.  Secondly, the spatial characteristics of piscine prey
favour a foraging strategy involving frequent changes in group size.  In
this system, kinship and dominance play reduced roles, while the apparent
lack of territoriality is typical of taxa confronted by heterogeneously
distributed resources.  The apparent preference by mature males for
associations with mature females may represent an attempt to establish
bonds with potential future mates.