Letter | Published:

Age Determination of Seals

Naturevolume 187pages959960 (1960) | Download Citation



A WORD of warning is necessary when the number of cementum rings in the canine teeth of seals is used to determine the age of some species of Phocidae. As Mansfield and Fisher1 have stated, they were able to count 18–20 rings in a tooth of a harbour seal (P. vitulina L.) of 19 years of age. For practical purposes this is good enough in the higher range of years, but the possible error becomes disproportionately large if applied to years 1–10 ; years which contain the critical years of sexual maturity both potential and actual. Great care is needed in assessing the age of young seals, since the doubt inherent in the statement ‘18–20’ is derived from real difficulties met with in counting the rings deposited in the earlier years of life, and in assessing the value of the ‘last’ ring.

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  1. 1

    Mansfield, A. W., and Fisher, H. D., Nature, 186, 92 (1960).

  2. 2

    Laws, R. M., Falkland Is. Depend., Survey, Sci. Rep., 2 (1953).

  3. 3

    Matheson, C., Nature, 166, 73 (1950).

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  1. Dept. of Zoology, Imperial College of Science and Technology, London, S.W.7

    • H. R. HEWER


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