Body mass and behaviour of stranded harbour seal (Phoca vitulina vitulina) pups during the peak pupping season in Co. Down, north-east Ireland

Abstract

Concerns have recently been raised as to whether small harbour seal pups found alone are genuine ‘orphans’, i.e. pups permanently separated from their mother. We present records of body mass and behaviour of pups live-stranding on the coast of north-east Ireland, between 1995 and 2016. Pup data were divided into three categories according to stranding date: period A from late May to 19 July (pupping period; 66 records), period B from 20 July to mid-August (late lactation and weaning period; 14 records) and period C from mid-August to the following January (14 records). Pup body mass averaged 8.8kg, 9.5kg and 14.5kg in periods A, B and C, respectively. Most pups in periods A and B were at or less than the average birth weight of ~11kg. Pre-stranding and stranding behaviours were video-recorded at haul-out sites for ten pups during period A and one during period B. The body mass and behaviour of pups considered to be orphans were compared with healthy ‘lone’ pups more than ten days of age, whose mothers were temporarily absent. The observations suggest that orphans may be identified—and distinguished from healthy lone pups—according to body size, location, behaviour and stranding date.