Subject: Abstract - humpback whales (fwd)

Mike Williamson (
Sun, 11 May 1997 10:59:54 -0400 (EDT)

Date: Sun, 11 May 1997 07:46:50 -0400
From: Phil Clapham <CLAPHAMP@NMNH.SI.EDU>
Reply-To: Marine Mammals Research and Conservation Discussion
Subject: Abstract - humpback whales

Barlow, J. & Clapham, P.J.  1997.  A new birth-interval approach to
     estimating demographic parameters of humpback whales.  Ecology
     78: 535-546.

A demographic model is developed based on interbirth intervals and is
applied to estimate the population growth rate of humpback whales
(Megaptera novaeangliae) in the Gulf of Maine.  Fecundity rates in this
model are based on the probabilities of giving birth at time t after a
previous birth and on the probabilities of giving birth first at age x.
Maximum likelihood methods are used to estimate these probabilities
using sighting data collected for individually identified whales.  Female
survival rates are estimated from these same sighting data using a
modified Jolly-Seber method.  The youngest age at first parturition is 5 yr,
the estimated mean birth interval is 2.38 yr (SE - 0.10 yr), the estimated
noncalf survival rate is 0.960 (SE = 0.008), and the estimated calf
survival rate is 0.875 (SE = 0.047).  The population growth rate (lambda)
is estimated to be 1.065; its standard error is estimated as 0.012 using a
Monte Carlo approach, which simulated sampling from a hypothetical
population of whales.  The simulation is also used to investigate the bias
in estimating birth intervals by previous methods.  The approach
developed here is applicable to studies of other populations for which
interbirth intervals can be measured.

Please send reprint requests to:

Dr Jay Barlow
SW Fisheries Science Center
Box 271
La Jolla, CA 92038

Phil Clapham
Smithsonian Institution