Data from: Group foraging increases foraging efficiency in a piscivorous diver, the African penguin

Marine piscivores have evolved a variety of morphological and behavioural
adaptations, including group foraging, to optimize foraging efficiency
when targeting shoaling fish. For penguins that are known to associate at
sea and feed on these prey resources, there is nonetheless a lack of
empirical evidence to support improved foraging efficiency when foraging
with conspecifics. We examined the hunting strategies and foraging
performance of breeding African penguins equipped with animal-borne video
recorders. Individuals pursued both solitary as well as schooling pelagic
fish, and demonstrated independent as well as group foraging behaviour.
The most profitable foraging involved herding of fish schools upwards
during the ascent phase of a dive where most catches constituted
depolarized fish. Catch-per-unit-effort was significantly improved when
targeting fish schools as opposed to single fish, especially when foraging
in groups. In contrast to more generalist penguin species, African
penguins appear to have evolved specialist hunting strategies closely
linked to their primary reliance on schooling pelagic fish. The specialist
nature of the observed hunting strategies further limits the survival
potential of this species if Allee effects reduce group size-related
foraging efficiency. This is likely to be exacerbated by diminishing fish
stocks due to resource competition and environmental change.