Geographic variation in vocalizations of pups and mother-pup behavior of harp seals Pagophilus groenlandicus

Abstract

All harp seal populations form breeding aggregations on the Arctic pack ice. However, pack ice conditions vary spatially and temporally among these aggregations with variation in envi- ronmental and oceanographic conditions, which may affect the behavioral interactions between mothers and their newborn pups. We investigated the variation in mother-pup behavior between harp seal breeding aggregations in the NE (Greenland Sea) and NW Atlantic coastal shelf region (Front). Acoustic cues provided by the pups are thought to be important in facilitating reunions with their mothers. Consequently, we measured variation in vocal parameters among seals to investigate geographic differences in pup vocalizations. Classification trees showed a distinctive split between Front and Greenland Sea pup vocalizations. There were no clear differences between male and female pups at the Front, where 42% of male and 38% of female pup calls could be attributed to a given individual. This contrasts with the Greenland Sea, where 55% of vocalizations of female pups were attributed to individuals compared with only 8% for males. Analyses of behavioral observations of mother-pup pairs made in the afternoon and evening showed that pups in the Greenland Sea suck- led more and were more alert than pups in the Front. Further, mother-pup attendance patterns dif- fered between sites. Mothers at the Front attended their pups 85.1% of the time, whereas mothers in the Greenland Sea attended their pups 52.2% of the time. These substantial differences between sites might be related to evolutionary changes in behavior resulting from commercial hunting or vari- able environmental conditions.