About trusting whales who are over age 30

From ANIMAL PEOPLE, July/August 1994:

ANIMAL PEOPLE reported in
June that according to a new Humane Society
of Canada study of all cetaceans known to
have been captured 1960-1992, captivity
cuts the average lifespan of orcas and beluga
whales by 43 years, and the average lifespan
of bottlenose dolphins by 15 years. It now
appears, however, that the HSC estimates of
orca and beluga lifespans in the wild were far
higher than current research indicates.
Cetacean ages are estimated by counting the
enamel layers on their teeth. Until 1984,
they were believed to grow one layer per
year. Then a postmortem on a 24-year-old
beluga who was kept in captivity from infan-
cy found that he had grown two layers per
year. Many references still state the old esti-
mates, but follow-up investigation has con-
vinced most marine mammologists to cut
those numbers in half. A study of captive
cetacean longevity by D.P. DeMaster and
J.K. Drevenak in 1988 produced similar aver-
ages to the HSC study––but also found that
the life expectancy for wild-caught dolphins
who survive their first year in captivity is 33
years, longer than dolphins live in the ocean,
while life expectancy for captive-born dol-
phins who survive to age one is 47 years.
First-year mortality is very high for
cetaceans––as for most animals––both in the
wild and in captivity.
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