ABSTRACT
The aims of this study were to (1) provide a general description of the hooded seal’s integument; (2) diagnose hair follicle activity stages and develop a chronology for the annual moult within the different sex and age classes; (3) examine the population characteristics of the moult haul-out; and (4) seek possible correlations between these events and the hooded seal’s annual cycle. Skin samples were collected from 68 moulting hooded seals out of 868 taken in the Denmark Strait for population studies during June and July 1972. The microstructure of the integument of this species is described. It varies little from what is known from other northern phocids. However, they appear to be one to two “intermediate” guard hair follicles within up to seven underfur follicles; these are smaller than the main guard hair follicle in each hair follicle complex. The hair follicles in the skin of most hooded seals of both sexes and all ages sampled between 21 June and 11 July 1972 were at early to middle stages of activity, suggesting that hair growth starts somewhat earlier than mid-June and ends later than mid-July. It appears that female moult haul-out numbers started to decline about four to five days earlier than the males, but when the haul-out began or ended could not be determined. The brevity, synchronicity and precision of the moult (and breeding season) suggest that its timing is controlled by an environmental factor such as day length at the high northern latitudes inhabited by hooded seals.
ABBREVIATION:
Acknowledgements
I am very grateful to the late Dr Torger Øritsland of the Norwegian Fisheries Directorate for inviting me to join and participate in the expedition’s programme. For the many courtesies, friendship and assistance extended to me by the expeditioners, ship’s captain and crew, I am truly grateful. Ms Tina Lavranos prepared the skin samples for microscopic study in the Medical School of the University of Adelaide; I am grateful for the use of the school’s equipment and facilities. I thank Drs Kit M. Kovacs and Tore Haug for encouraging me to publish this old work, and I thank Dr Kovacs for transforming my original text into electronic journal format. Two anonymous reviewers made many helpful comments on the manuscript.
Disclosure statement
No potential conflict of interest was reported by the author.