Subject: Whale aging & repro -- summary (fwd)

Mike Williamson (pita@www1.wheelock.edu)
Tue, 12 Aug 1997 17:35:21 -0400 (EDT)

Subject: Female whale aging & repro -- summary

Many thanks to the MARMAMers who responded to my queries about reproduction
in aged cetaceans.  A quick summary of comments I've gotten:

I asked about
> a statement in an encyclopedia that some baleen whales
>continue breeding at > 90 years of age; could anyone confirm & suggest
>where the original observation comes from?  NB, this is not longevity per
>se, but actual breeding...

The only data seems to be on fin whales, and it seems a little unclear;
some people have estimated age using corpora and others using ear laminae,
and with the later there's evident ambiguity in early reports whether a
layer meant a pair of alternating bands or each band; on a quick reading of
responses, I get the feeling the problem has not been clearly hammered out
with respect to interpreting early accounts of old females (to the degree
biggest whales were taken first and size correlates with age, _only_ early
accounts _could_ discuss old females.  Are any of the original "100
laminae" earplugs sitting in museum drawers available for recounting with
clearly-defined terms?).  Conservatively, it seems secure that [at least
some] fin whales continue breeding past age 50, there seems reasonable
concensus at > 60, and I've received varying [definitive!] opinions on >70
years; females _aged_ to 75 or 80 seems secure.  Nobody seems to have
_data_ on a 90-year old, so that seems like speculation/error, BUT worth
noting that if one assumes the biggest/oldest whales were killed early, and
not all were sampled thoroughly, then the odds that scientists would've
gotten _the_ oldest are slim indeed -- so while 90+ is speculative, it's
not a bad speculation.

It was noted that there's the bowhead estimates of 100 year age (stone
harpoon point found in 1993 etc),  and Chittleborough (1965) reported a
48-year old humpback (though in a depleted stock, again, older ones likely
already gone).


There was an interesting comment that
>Alex Aguilar also had a 60+ year-old pregnant female fin whale, and
>notes that the contaminant burdens of female fin whales dont ever seem
>to rise after sexual maturity, which you'd expect them to after repro
>senescence had set in and they stopped dumping their contaminants
>through lactation.

I wonder though whether there's a problem with the life stage at which
contaminants start to be accumulated; the older whales were presumably
mature before ocean dumping of many organics became serious problem, could
that affect contaminant dynamics?  Anyhow, that's less direct than the ear
laminae/corpora data...

==========
AND
>if there is any evidence for post-reproductive females
>in orcas (analogous to Kasuya & Marsh's findings for pilot whales)?

        In the wild, first births have been recorded at between 10-20 years
(that's known range, not approximation).  Some ("about 17") adult-sized
females in the 1970s had not given birth as of 1993 and this presumably
represents either a long postreproductive career or an alarmingly high rate
of unexplained pathological sterility (there _is_ evidence for baren
females, but at a lower rate).  Best guess based on Puget Sound
demographics is that females typically bear last calves at ca. 40 years
old, and may live for 20+ years more after that.  Note I am guessing that
if age of 1st birth varies over a 10-year span, that "ca. 40" is bound to
be pretty loose.

Summed nicely in Sara and James Heimlich-Boran's _Killer Whales_, in which
they write: "Using a variety of estimates, it appears that half of all
killer whale
females older than 39 have stopped giving birth and by the age of 55, all
females are post-reproductive. Although there is no direct proof that
ovulation has ceased, biological studies on short-finned pilot whales, a
closely related species, have shown a lack of ovulation in females over the
age of 40. This strongly supports the existence of this later life stage in
female killer whales. It has been estimated that one-third of all adult
females in the Pacific Northwest resident communities are post-reproductive."

=============

Also got a note that some female grey seals are pupping away at age 34+!

Thanks to
Robin Baird, Trisha Lamb Feuerstein, Jeff Jacobsen, Christina Lockyer, Lori
Marino, Peter Olesiuk, Paddy Pomeroy, Dale Rice, and anyone I forgot...

Relevant refs:
Alex Aguilar and Christina Lockyer (1987 in Can J Zool)

Baird, R.W. In press. The killer whale - foraging specializatons and
group hunting. In: Dolphins and Whales: Field Studies of Behavior.
Edited by P. Tyack, R. Connor, J. Mann and H. Whitehead. University
of Chicago Press.

Christensen, I. 1984. Growth and reproduction of killer whales, Orcinus
orca, in Norwegian coastal waters. REPORT OF THE INTERNAL. WHALING COMM
(Special issue 6).

Laws (1961) Reproduction, growth and
age of southern fin whales "Discovery" Reports vol.31, pp.327-486.

Olesuik, Bigg, & Ellis.1990. Life history and pop. dynamics of resident
killer whales... REP. OF THE INT. WHALING COMM. (Special issue 12).

Kirkevold, B.C. & J.S. Lockhard. 1986. BEHAVIORAL BIOLOGY OF KILLER
WHALES. Liss: NY.

     Nishiwaki, M., Ichihara, T., and Ohsumi, S.  1958.  Age studies of fin
     whale based on ear plug.  Scientific Reports of the Whales Research
     Institute 13:155-169.

     Ohsumi, S.  1964.  Examination of age determination of the fin whale.
     Scientific Reports of the Whales Research Institute 18:49-88.

Pryor, K. & Norris, K. S. (1991). Dolphin Societies: Discoveries and
Puzzles. Berkeley: University of California Press.
========================
Some primate menopause refs, for context:
Leidy, L. E. (1994). Biological aspects of menopause: across the lifespan.
Ann. Rev. Anthropol. 23: 231-253.

Pavelka, M. S. M. & Fedigan, L. M. (1991). Menopause: a comparative life
history perspective. Yrbk. Phys. Anthropol. 34: 13-38.

Rogers, A. R. (1993). Why menopause? Evol. Ecol. 7: 406-420.

Walker, M. L. (1995). Menopause in female rhesus monkeys. Am. J. Primatol.
35: 59-71.

THANKS AGAIN!
Jim

--------------------------------------------------------------
Jim Moore
Anthro 0532, UCSD               Statistics is never having
La Jolla CA 92093               to say you're sure...
fax 619 534-5946
jjmoore@ucsd.edu                                        or is it?