Data from:The foe you know: Observations of interspecific interactions between small cetaceans and northern resident killer whales (Orcinus orca) in the northeast Pacific

We documented the first aerial observations of interspecific interactions
of fish-eating, northern resident killer whales (Orcinus orca) with two
small cetacean species, Dall’s porpoises (Phocoenoides dalli) and Pacific
white-sided dolphins (Lagenorhynchus obliquidens), off northeastern
Vancouver Island, (British Columbia, Canada). Specifically, we used
drone-collected data to compare observations of porpoises and dolphins
interacting with northern resident killer whales to understand factors
which may promote interspecific interactions. From 2018 to 2021, 42
interactions were opportunistically recorded of Dall’s porpoises (19%),
Pacific white-sided dolphins (74%), and both species (7%) approaching
groups of travelling, milling, socializing, and resting northern resident
killer whales. The mean group size of killer whales during interactions
with dolphins (an average of 8 killer whales) and porpoises (an average of
3 killer whales) was significantly different. Porpoises interacted only
with small groups (n ≤ 5) of killer whales, while dolphins interacted with
larger groups (n ≤ 25). This suggests that the likelihood of interaction
by each species is influenced by killer whale group size. However, the age
and sex composition of killer whale groups, as well as the number of small
cetaceans present, were found to have no significant effect on interaction
patterns. Additionally, we never observed killer whales initiating
interactions. We discuss several adaptive benefits, including
antipredator, foraging, hydrodynamic, and social advantages, to dolphins
and porpoises which may drive the observed interactions. The benefits of
interactions appeared to be predominantly antipredator-focused and
species-specific, with both species possibly also benefitting from
increased hydrodynamic efficiency whilst swimming. While opportunistic,
our observations provide detailed accounts of non-predatory interactions
between small cetacean species and northern resident killer whales. Future
studies focusing on the drivers of mixed-species group formation in the
North Pacific are needed, and we suggest that these utilize drones as a
platform for data collection.