Moult and changes in body shape and pelage in known‐age male New Zealand sea lions (Phocarctos hookeri)

Abstract

We observed a small population of male New Zealand sea lions (Phocarctos hookeri) in 7 consecutive years at Otago, New Zealand, a region north of the main breeding population. Changes in pelage, body shape, and body length, with growth of tagged, known‐age males were used to define age class categories: “juvenile” (1–3 years), “subadult” (4–5 years) and “adult” (6 years and older). Accurate assessments of age are important to determine immigration rates of cohorts into a small population. We used photographic identification to recognise individuals so that the progression of moult could be determined. Individuals 2+ years old underwent a complete annual moult over a period of c. 2 months between December and June. Juveniles moulted earlier than subadults and adults. However, 1‐year‐old males underwent only a partial annual moult. Knowledge of the timing of moult is important for the deployment of remote sensing devices glued to the pelage, because moult will result in the loss of attached equipment.