Subject: LIFE EXPECTANCY OF WHALES (fwd)

Michael Williamson (pita@whale.simmons.edu)
Wed, 16 Oct 1996 08:21:57 -0400 (EDT)

Date: 15 Oct 96 21:02 EST
From: CLAPHAM.PHIL@SIMNH.SI.EDU
To: "G.ask [Private Mail Group]"@SIMNH.SI.EDU,
    "RWHITE@IAMERICA.NET"@SIVM.SI.EDU
Subject: Copy of: LIFE EXPECTANCY OF KILLER WHALES

Original message: "LIFE EXPECTANCY OF KILLER WHALES"
From: <<rwhite@iamerica.net>>

I've looked everywhere (almost) trying to find the average life
expectancy of whales, killer whales in particular.  could you please
list them for me?  please reply to rwhite@iamerica.net.

thanks!

Hi:

Part of the reason you had a hard time finding anything is because, in many
cases, there is a good deal of uncertainty.  here's a sampling of what we
know (and don't know);

Killer whales: this is coming from my memory, but I'm fairly certain
that work conducted in long-term studies of identified individual
killer whales in the Pacific Northwest by Mike Bigg, John Ford and
colleagues provides strong evidence that these animals are long-lived.
It is thought by many killer whale biologists that life expectancy of
some female killer whales might exceed 80 years.  (Pause while he looks
something up...)  OK, here's something from a paper by P. Olesiuk and
colleagues:

  "Eight females, six of which were still alive in 1987, attained
   ages of greater than 60 years.  The two oldest females were
   estimated to have been 76.5 and 77.5 years of age when last
   seen in 1987.  Thus maximum longevity of females likely
   extended to at least 80 years... possibly as old as 90 years...
   Life tables suggested that male longevity was likely on the
   order of 50-60 years."

  This was from killer whale populations in Washington state and British
Columbia, from a paper published in 1990.

  As for the large baleen whales, we know a good deal about some, less
about others.  Some species can be aged (if the animal is dead) by
extracting and examining a waxy hard plug that grows in the ear of the
animal (incidentally, this seems to actually assist hearing, not impair
it).  The plug puts on a number of layers each year, so is rather like
tree rings in that you can figure out how old the whale is - assuming
you know how many layers are laid down annually (also, the layers
are linear, not concentric as in trees).  In fin whales, for example,
there is not much dispute that the ear plug grows at two layers a
year, and from this we know that finbacks are very long-lived.  Females
and males of close to 80 years (160 ear plug layers) are not unknown
from whaling catches.

  In humpbacks, which also have ear plugs, there is more dispute about
the layers per year.  This is a long story, but suffice to say that in
the 1960's an Australian biologist named Graeme Chittleborough said
he thought it was four layers a year, and that humpbacks lived to around
50 - although he pointed out that as most whales had been killed by whaling
we didn't know whether this was an underestimate or not.  His work was
disputed, but a study conducted by myself and Dr Charles Mayo a few
years ago, on living humpbacks in the Gulf of Maine, pretty much confirmed
that he'd been right.

One of the really interesting animals is the bowhead whale.  A recent
technique which looks at stable isotope accumulation in the baleen of
bowheads suggested that they were much longer-lived than most people
thought.  This has recently been more widely accepted, and potentially
confirmed by an interesting event.  In May 1993, a very large (54 foot)
male bowhead was killed by the Alaskan Inuit.  In its side were two
stone harpoon points, one of which was last known to be in use in 1881,
and not later than 1900.  It seems likely that this whale had been
carrying around this harpoon point for the better part of a century
(I recently had the privilege of holding it in my hand, and it was
a very cool experience!)

Other whales: blue whales are probably the same as fin whales in their
life expectancy.  Right whales might well be similar to bowheads; we know
of one distinctively marked animal that was photographed in 1935, and
several times long after that - the most recent being 1994.  Since she
had a calf in 1935, she would have been at least 8-10, so is probably
close to 70 today.

Hope this answers the question!

Phil Clapham

Phil Clapham