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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