Breeding behavior and pup development of the Caspian seal,Pusa caspica

Abstract

The Caspian seal, Pusa caspica, is an ice-breeding phocid endemic to the Caspian Sea. The breeding behavior of this species is poorly documented. Here, we report behavioral observations of 518 mother-pup pairs and 210 lone pups, made from the bridge of icebreakers traversing seal breeding grounds while servicing oil installations in the northeastern Caspian Sea, during 34 trips from late January to early March, 2006-2012. The breeding habitat of Caspian seals is land-fast or drift ice, usually at least 20 cm thick, overlying water 3–5 m deep. Pregnant females formed pairs or small groups. They were not observed to use lairs, but preferentially pupped beside ice ridges or ice-slab piles that afforded shelter to pups. In years when there were few natural leads into the ice-field, females often gave birth on the edge of artificial leads formed by shipping channels. Pups were categorized into stages from newborn (1), white-coat (2), molting (3), and molted (4), with Stage 3 and 4 pups appearing from mid to late February. The nursing period lasted at least 3 weeks and neighboring mother-pup pairs appeared to be mutually tolerant. Mothers left their pups alone or at nursery sites, presumably to forage. Most white-coat pups moved over the ice while avoiding water in response to disturbance from vessels. Mother-pup pairs maintained contact while moving across the ice by a combination of the pup’s following response and diligent chaperoning by the mother. During disturbances some lone pups sought refuge in shelters under ice slabs, whereas others followed a neighboring mother-pup pair away from the vessel. Male-female pairing occurred in late season with no male-male competition observed on the ice. While breeding and pup rearing behavior of Caspian seals has some features in common with that of other Holarctic seals, it is largely distinct and adapted to the unique conditions of the Caspian environment, in particular the paucity of snow cover on the ice.