
%0 Journal Article
%A Childerhouse, S. 
%A Dickie, G. 
%A Hessel, G. 
%T Ageing live New Zealand sea lions (<emph type="2">Phocarctos hookeri</emph>) using the first post-canine tooth
%J Wildlife Research
%D 2004/05/26
%V 31
%N 2
%P 177-181
%K 
%R https://doi.org/10.1071/WR03006
%U https://www.publish.csiro.au/paper/WR03006 
%X Live New Zealand sea lions (Phocarctos hookeri) were aged from growth layer groups (GLGs) in the cementum of a lower first post-canine tooth. A single post-canine (PC1) was removed from individuals of known-age (n = 74) between 1997 and 2001 while under a full anaesthetic. Teeth were decalcified, sectioned on a cryostat, stained and then mounted on glass slides. Age was estimated by counting GLGs in the cementum multiple times. Age estimates were calibrated with known-aged individuals and confirmed the annual formation of cementum annuli in PC1 tooth. While there is some variation in assigning exact age to individuals, it was possible to age 94% of teeth to the exact year or to within 1 year of actual age. There was no significant difference in the slope of regression lines associated with actual and estimated age using this technique (t-test, t = 0.309, d.f. = 144, P &#60; 0.05). Accuracy in ageing was improved by discarding sets of readings with low precision and re-reading the tooth until a precise set of estimates was made. GLGs in the cementum were more accurate and robust for age estimation than using GLGs in the dentine. This paper describes a reliable method for the preparation and ageing of the first post-canine tooth (PC1) from live New Zealand sea lions. 
