Diving behaviour of lactating bearded seals (Erignathus barbatus) in the Svalbard area

Summary

This study documents activity patterns and diving behaviour of four bearded seal (Erignathus barbatus) mothers during the lactation period. The females spent 8 +/- 3% (mean +/- SD) of their time hauled out on the ice and 92 +/- 3% in the water. Approximately half of their time was spent diving. During the study 15 077 dives were recorded. The duration of dives was 2.0 +/- 2.3 min and diving depth was 17.2 +/- 22.5 m (maximum 18.7 min and 288 m, respectively). Haulout periods occurred 3 +/- 2 times per day (duration = 44.0 +/- 98.1 min). The overall distance swum per day was 48.1 +/- 23.2 km. Three dive types were differentiated using a combination of hierarchical and k-means clustering, one V-shaped grouping and two U-shaped groupings. The most common dive type was U(1); these dives were the deepest and longest type (depth = 28 +/- 32 m, duration = 185 +/- 146 s), and bottom time occupied a significant fraction of the total dive time (120 +/- 120 s). These dives are likely foraging dives. Lactation is energetically demanding for bearded seals, and females do forage while they have dependent pups.