We would like to announce the publication of the following paper:
H. Whitehead and S. Gero (2015) Conflicting rates of increase in the sperm whale population
of the eastern Caribbean: positive rates do not reflect a healthy population. Endangered
Species Research 27: 207–218
Abstract:
Observed rates of increase calculated from trends in the numbers of animals present in a
population should generally agree with those estimated from life-history data. However, for a
small population of individually identified sperm whales
Physeter macrocephalus occupying
the waters of the eastern Caribbean there is a discrepancy. Using a mark-recapture analysis
that included heterogeneity in identification, the population, numbering about 156 adults (95%
CI 126−195) in 1998, has been increasing at 3.4% yr−1(95% CI: 1.0−5.7% yr-1). However, a
2-stage matrix population model including unweaned calves and adults (and excluding
mature males), whose parameters were estimated directly from empirical data, gave a
projected rate of increase of −2.7% yr−1(95% CI: −5.4 to −0.4% yr−1). This estimate is
primarily sensitive to calculated adult mortality. The discrepancy between the observed and
projected rates of increase for this population may be explained by a high, probably
anthropogenic, mortality of sperm whales in the eastern Caribbean, coupled with immigration
from surrounding regions, so the area becomes an attractive sink (ecological trap). The
analysis emphasizes the fragility of sperm whale populations. More generally, our analysis of
this population shows that a positive observed rate of increase is not necessarily a sign of a
healthy population. This case study highlights the importance of analysing populations of
endangered species using multiple methodologies and with a solid base of individual-level
empirical data based on longitudinal monitoring.
The paper is Open Access at:
http://www.int-res.com/articles/esr2015/27/n027p207.pdf
Hal Whitehead
Dalhousie University
hwhit...@dal.ca
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