Subject: Whale Age: Reproduction in old whales (fwd)

Mike Williamson (pita@www1.wheelock.edu)
Tue, 12 Aug 1997 17:42:05 -0400 (EDT)

Subject: Re: Reproduction in old whales


          I regret to say that Phil Clapham's conclusions concerning
          the data in the paper by Nishiwaki (1958) are incorrect.
          Many readers have become confused by the sloppy terminology
          used in the late 50s and early 60s when "lamination" and
          "growth layer" were used more or less interchangeably.  It
          was not until the IWC Scientific Committee held a special
          meeting on age determination in Oslo in 1968 that it was
          decided that two "laminations" (a light OR a dark layer)
          equaled one "growth layer" (a light AND a dark layer).

          Nishiwaki (1958) did indeed suggest that two "laminations"
          (=growth layers) were laid down each year.  That was the
          prevailing idea in those days, as first suggested by Laws
          and Purves in 1956 (although there were virtually no data to
          support it).  However, data from many later studies,such as
          that by Ohsumi (1964) which I cited, showed that the
          accumulation rate could not possibly be two growth layers
          per year, but was consistent with a rate of one growth layer
          per year (although the rate in sexually immature animals is
          debatable).

          In summary, the "laminations" in Nishiwaki (1958) are what
          are now called "growth layers" (or "growth layer groups"),
          and the weight of evidence is that they are laid down ca.
          annually.


          Following are some of my own data on female baleen whales
          taken off California (gl=growth layers):

          FIN WHALES: Oldest lactating 43 gl; Oldest pregnant  42 gl;
          Oldest in sample  48gl.; N=375.

          SEI WHALES: Oldest lactating  48 gl; Oldest pregnant  48 gl;
          Oldest in sample 48 gl.; N=183.

          HUMPBACK WHALES: Oldest lactating 53 gl; Oldest pregnant 47
          gl; Oldest in sample 62; N=118.

          BLUE WHALES: Oldest pregnant 33 gl; Oldest in sample 46 gl;
          N=13.

          Dale W. Rice
          dale.rice@noaa.gov

          ______________________________ Reply Separator
          _________________________________
          Subject: Reproduction in old whales
          Author:  CLAPHAMP@NMNH.SI.EDU at EXTERNAL
          Date:    12/08/1997 9:19 AM


          ** High Priority **

          If I am reading the paper correctly, Dale Rice's message
          concerning age data on old fin whales, taken from Nishiwaki
          et al (1958), is misleading. Dr Rice quotes a figure of 100
          laminations for a lactating female and links this to
          Ohsumi's estimate that 1 lamination per year is laid down.
          This implies that a 100-year-old female was lactating.

          The Nishiwaki paper, however, states the following (page
          155):

          "It is considered in our studies that 2 laminations are
          deposited in one
          year in the ear plug."

          This is repeated later on in the paper, and echoes current
          opinion that the growth rate is one Growth Layer Group (one
          light, one dark lamina) per year.

          Consequently, all of the figures in this paper (given in the
          Appendix) should be divided by two, not one, to get an
          approximate age of the animal in question.

          Alex Aguilar and Christina Lockyer (1987 in Can J Zool)
          looked at animals in the Spanish catch and found fin whales
          with up to 80 GLG's (i.e. 80 pairs of laminae, implying an
          age of around 80 years).  If I recall correctly, Alex also
          had an animal that was pregnant in her 60's, but to my
          knowledge there is no record of a greater age for active
          reproduction in baleen whales.

          Phil Clapham
          Smithsonian Institution
          claphamp@nmnh.si.edu