Attendance and nursing patterns of harp seals in the harsh environment of the northwest Atlantic

Abstract

Harp seals are capital breeders who give birth to single pups and nurse them with fat-rich milk for 12 days on pack ice in the North Atlantic under harsh environmental conditions. Our objective was to examine female attendance and nursing patterns under varying environmental conditions to determine whether these patterns change in response to changing weather conditions. The behaviour of 158 harp seal females and pups off north-eastern Newfoundland was recorded every 3 min during daylight hours. Air and water temperature, and wind speed were recorded at the beginning of each observation session. We constructed GAMM models to examine the importance of these variables in predicting attendance and nursing patterns. The best model for predicting attendance included time of day, air temperature, wind speed, and the interaction between wind and air temperature. The best model for predicting nursing included wind speed, air temperature and time of day. Females were more likely to attend their pups during the afternoon when solar radiation appeared to be high, but reduced attendance during high winds and/or low temperatures. The likelihood of attending females nursing during these poor weather conditions was greater than when conditions were better. Thus, females were less likely to be present when weather conditions were poor but when present, they were more likely to be provisioning their pups. This strategy may help these females defray the thermoregulatory demands on their limited resources while ensuring that their young attain weights that are likely to increase post-weaning survival and hence maternal fitness.