Orcas are apex predators of the ocean, capable of taking down a variety of species and even the occasional yacht. However, in Iceland, there are orca groups that specialize in hunting fish, in particular herring. Observations in different years have revealed juvenile pilot whale calves among these groups – so were the orcas trying to eat, play with, or even nurture the calves?
On June 23, 2022, a juvenile pilot whale was observed within a pod of orcas. The pilot whale was “of very small size and with visible fetal folds,” write the authors of a recent paper detailing the observation. The calf was within a group of 11 adults and five young orcas who could be identified by the boat survey, while two juveniles could not be. The researchers thought that this group was primarily made up of fish specialists who have been seen in herring winter and summer spawning grounds.
The pilot whale calf was seen surfacing and swimming slightly to the side and behind a female orca, in a position known as the echelon position that is typically seen in mother-calf whale pairs. At certain points, an adult orca seemed to nudge the calf along.
Observation of the pilot whale calf was only seen that day, and the team does not know what happened to the juvenile after, or how it came to be with the group in the first place.
Then, almost a year later, on June 20, 2023, a pilot whale calf was again spotted within a group of orcas. As before, this group of orcas was known to the team as herring specialists. The calf was seen in an echelon position, though at one point was observed being lifted out of the water by an adult killer whale. The same group was seen again the following day without the pilot whale calf, and the calf was never sighted again.
Despite this interaction, there were no observations of aggression or injury to the pilot whale calf.
There are a few theories that the researchers have about why the two calves ended up within the group of orcas. One idea is that the orcas were exhibiting predatory behavior. However, these are known fish specialist groups, and the calf was seen with no visible injuries, suggesting this was not the case in these two interactions.
The team thinks that either the orcas could have just been playing with the young pilot whale, or were using the juvenile as a means to practice hunting. These whales are known to herd herring into bait balls, and the position of the pilot whale between two orcas in the first observation could indicate a herding technique. The whales could also be practicing some kind of nurturing behavior on the juvenile.
“It could be [that the orcas] encountered the pilot whale opportunistically, and some individuals played with the whale, and others tried to nurture it,” lead author Chérine Baumgartner told Scientific American.
The team also ruled out aggression-based behaviors and infanticide, but they do consider how the pilot whale calves came to be with the orcas in the first place. It is possible that the orcas approached a pilot whale group to get a calf, or that the calf was lost and happened upon by the orcas.
Given that each event was only observed once and the outcome and context are unknown, the authors suggest that it is “difficult at this point to conclude on a single, definitive interpretation of the proximate or ultimate causes of these interactions and it is possible that they have multiple drivers”.
Interestingly, the same behavior was also seen in the west of Iceland in 2021, reports a different study; this was attributed to alloparental care, though the team suggests there might be multiple reasons for the behavior seen.
Elsewhere in the animal world, capuchins have been stealing baby howler monkeys, and spoiler alert – it does not end well.
The study is published in Ecology and Evolution.
Source Link: Orcas Spotted Hanging Out With Pilot Whale Calves – What’s Going On?
