Deep-diving beaked whales dive together but forage apart

Echolocating animals that forage in social groups can potentially benefit
from eavesdropping on other group members, cooperative foraging or social
defence, but may also face problems of acoustic interference and
intra-group competition for prey. Here, we investigated these potential
trade-offs of sociality for extreme deep-diving Blainville´s and Cuvier’s
beaked whales. These species perform highly synchronous group dives as a
presumed predator-avoidance behaviour but the benefits and costs of this
on foraging have not been investigated. We showed that group members could
hear their companions for a median of at least 91% of the vocal foraging
phase of their dives. This enabled whales to coordinate their mean travel
direction despite differing individual headings as they pursued prey on a
minute-by-minute basis. While beaked whales coordinated their
echolocation-based foraging periods tightly, individual click and buzz
rates were both independent of the number of whales in the group. Thus,
their foraging performance was not affected by intra-group competition or
interference from group members, and they did not seem to capitalize
directly on eavesdropping on the echoes produced by the echolocation
clicks of their companions. We concluded that the close diving and vocal
synchronization of beaked whale groups which quantitatively reduces
predation risk has little impact on foraging performance.