Subject: Abstract: whale mating strategies (fwd)
Mike Williamson (pita@www1.wheelock.edu)
Sat, 13 Dec 1997 15:32:16 -0500 (EST)
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---------- Forwarded message ----------
Date: Fri, 12 Dec 1997 14:25:09 -0800
From: MARMAM Editors <marmamed@UVic.CA>
Reply-To: Marine Mammals Research and Conservation Discussion
<MARMAM@UVVM.UVIC.CA>
To: MARMAM@UVVM.UVIC.CA
Subject: Abstract: whale mating strategies (fwd)
Forwarded message:
From: Dagmar_Fertl@mms.gov (Dagmar Fertl)
Thought the following might be of interest to some folks (please don't
send reprint requests to me though).
*******************
Magnusson, KG; Kasuya, T. 1997. Mating strategies in whale
populations: searching strategy vs. harem strategy. Ecological
modelling 102: 225-242.
This work develops a probability model for comparing two different
male mating strategies in whale populations where females group
together in pods and are only receptive for a fraction of the breeding
season. A searching strategy and a harem strategy are modelled
and the probabilities that a given female becomes pregnant derived for
the two strategies and compared. The advantage one strategy
has over the other in terms of pregnancy rates depends on four key
parameters: the number of oestrus cycles in a breeding season
(m), fraction of time in the season when a female is in oestrus (q),
ratio of number of males to number of female pods (r), and the
expected number of pods found by a male in a breeding season (alpha).
Situations in which a searching strategy is best are intuitively
reasonable, i.e. a high value of q and/or a high value of alpha. The
theory is then applied to two species of social cetaceans:
short-finned pilot whales and sperm whales. Non-reproductive matings
are practised by short-finned pilot whales and it is
hypothesized that this behaviour entices males to stay with the pod,
i.e. to adopt a harem strategy. The benefits females derive from
this behaviour in terms of increased pregnancy rates are then
evaluated. Very limited information exists concerning the value of the
relevant parameters for the two species, but what little there is,
suggests that sperm whales are in the region of parameter space
where the searching strategy is better, but that short-finned pilot
whales are in the harem region.
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