Part I: Seals teeth and whales ears - Scott Polar Research Institute ...

was probably the first time that such methods had been successfully applied to a
large mammal in the wild.
Moreover there was an opportunity to check my results. Long after my earlier
work in 1948-51 Carrick and Ingham (1960) published an important paper that
provided remarkably close confirmation of the accuracy of my age data and
population models. This confirmed the validity of dentinal growth layers for estimating the
age of the species. Through the kindness of Robert Carrick I was able to examine
photomicrographs of teeth from elephant seals branded as pups and later resighted
at various ages. They also analysed data from Heard Island on long-term survival of.
Their estimates of the total recruitment at birth at Macquarie and Heard Island was
110,000 pups and a maximum population of 3.5 times this. This was in remarkably
close agreement with my estimate of potential 3.8-3.2 times (mean 3.5) for an unexploited
herd at South Georgia. They also concluded that there was a 27% survival rate for 6-year-old
females at Macquarie Island, amazingly close to my figure of 27.50% for the 6-year-old female
cohort at South Georgia!
In conducting the work I had been virtually on my own, isolated from fellow
biologists – except for the enjoyable year at South Georgia, when I was able to
discuss ideas with Arthur Mansfield, a fellow zoologist. (There was no e-mail then.)
I had no access to computers (taken for granted today), or even to a calculating
machine. Life tables in research on wild mammals had only just come into play. I
had applied concepts like catch per unit of effort to investigating historical trends in
a harvested/exploited wild mammal population, probably for the first time(?). The
fieldwork was conducted under rigorous environmental conditions. Added to all
this, the size of my ‘experimental’ animal – up to four tons in weight and up to 6 m
or more in length, was daunting. I had combined detailed anatomical, physiological,
behavioural and mathematical methods at Signy Island and South Georgia to build a
body of knowledge - most of it new to science – which was not merely of basic
interest. It had also led to the formulation of a management and conservation
strategy that rescued a species from over-exploitation and provided for monitoring
and testing of hypotheses. Furthermore it was my first venture in research, with
minimal resources and virtually no supervision. I had to be self-reliant and this
suited me well. It was also, I think, a key component, and one of the peaks, of my
research career; a time when I enjoyed to the full the joy of discovering new facts and
paradigms, tested and confirmed over a longer period by prediction and monitoring.
In consequence, I formulated new legislation and proposed, introduced and
supervised a new control/management system for overseeing the progress of a small
industry.
I saw this work as only a beginning and was aware of the need for more precise
information on life tables and population models, and changes in them with time.
Weight-at-age data were sparse, more work was needed on sex ratios and optimal
harem size under exploitation, and pregnancy rate data were sparse. Information on
changes with time in the relative and absolute abundance of seals along different
parts of the coastline, and better estimates of most parameters of the population was
needed. Finally, I should say that this innovative study, done in parallel with my
PhD was not included in my dissertation. Owing to the length restriction it was
entitled “The Reproduction of the Elephant seal” and my work had gone much,
much farther than that.
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