Cooperative feeding in cetaceans
Cooperative feeding comes about when two or more individuals effectively capture more and/or bigger prey items and suffer fewer costs together than alone. A number of mammal species, and even one bird species has been reported to undertake cooperative hunting, which could range from simultaneous chases, or clearly coordinated attacks. Coordinated attacks involve the division of labour, with individuals fulfilling different roles or subtasks, and often during repeated cooperative feeding will specialize in their roles. Role specialization in cooperative feeding is in fact quite rare.
While most mysticetes (baleen whales), with the exception of the humpback whale, forage independently, the odontocetes (toothed whales) will often travel and feed in large groups. Cooperative feeding is relatively well described for cetacean species such as killer whales Orcinus orca, bottlenose dolphins Tursiops truncatus, and humpback whales Megaptera novaeangliae.
Killer whales feed on a variety of prey items including fish, seals, and birds. Seal-eating killer whales have a distinctive cooperative feeding method: after locating a seal on an ice floe by spyhopping, they will coordinate to tip the ice floe by pushing it from beneath, break the ice floe apart, or wash waves of water over the ice by swimming in a line just below the surface diving at the last moment sending a large wave over the floe, ultimately landing the seal in the water and their waiting jaws.
Cooperative feeding in bottlenose dolphins is primarily observed with fish as the prey item, and includes: fish being herded into a ball, fish being driven by a dolphin into a waiting crescent of dolphins or against mud banks, or trapped between dolphins attacking from either side. Dolphins may even beach themselves onto mud banks to catch fish they had chased there. Cooperative feeding in bottlenose dolphins is one example of division of labour with role specialization. A ‘driver’ dolphin herds the fish into a ball as well as towards a group of ‘barrier’ dolphins waiting in a crescent, and the same individuals fulfil these roles in each group foraging in this way.
Humpback whales also exhibit cooperative feeding, often with the use of a bubblenet. One or more whales will swim in a large spiral blowing bubbles (either throughout the spiral or only during portions of it) to encase and concentrate a school of fish or euphasids within a bubble-net. Individuals in a group will then coordinate their lunging through the centre of the bubble-net. The thought is that some fish may inadvertently escape from one mouth only to land in another’s, and larger schools of more mobile fish may be easier caught by a group of whales than an individual.
Written by: Minke Tolsma
For further reading:
- Gazda, S.K., Connor, R.C., Edgar, R.K. and Cox, F. 2005. A division of labour with role specialization in group-hunting bottlenose dolphins (Tursiops truncatus) off Cedar Key, Florida. Proceedings of the Royal Society B 272: 135-140.
- Pitman, R.L. and Durban, J.W. 2012. Cooperative hunting behavior, prey selectivity and prey handling by pack ice killer whales (Orcinus orca), type B, in Antarctic Peninsula waters. Mammal Marine Science 28: 16-36.
- Wiley, D., Ware, C., Bocconcelli, A., Cholewiak, D., Friedlaender, A., Thompson, M. and Weinrich, M. 2011. Underwater components of humpback whale bubble-net feeding behaviour. Behaviour148: 575-602.