Researchers investigated what caused cooperative hunting to evolve in solitary animals. The researchers hypothesized going into the investigation that cooperative hunting behavior was either the cause of sociality in animals or a consequence of it. The researchers gathered data primarily on cooperative hunting in fossas in the Kirindy Forest in Madagascar. The primary way data was collected in this study was through observation of a fossas hunt.The observation was made during the dry season in Madagascar (May - October) where droughts in both food and water are common. Researchers found that although fossas are usually solitary outside of their breeding season, they will hunt together during the drought season to boost their chances of success on a hunt. The researchers observed one hunt where three fossas hunted a group of sifakas. The fossas worked together in their hunt by using a strategy where the fossas would chase a sifaka into a tree and one fossa would chase the sifaka into the tree while the other two fossas waited at the bottom of the tree to catch the sifaka when it tried to flee. During the feeding time after the hunt, the fossas took turns feeding on the corpse of the sifaka with no disputes between them. After the feeding was done, the three fossas left together to either continue to hunt or make their way back to their beds for the night. From this observation the researchers concluded that cooperative hunting may have evolved as a result of necessity in hunting particularly agile or large prey. A solitary animal may have trouble hunting an animal that is larger or faster than it so cooperative hunting evolved out of necessity for that.  Alternatively, the researchers also came up with the hypothesis that cooperative hunting evolved from the need to protect a territory from predators. For example, a single fossa would be unable to defend a territory from predators or competing species that would be looking to steal the hunting grounds of the territory, but a group of fossas would be able to defend a territory and ensure a safe, stable hunting ground to get food in. This research is helpful in advancing our understanding of how cooperative hunting has evolved by offering two explanations for why the behavior exists. However this study was only done on a small number of hunts by one species of animal and therefore may not necessarily apply to other species that partake in cooperative hunting. Further studies into other species would have to be conducted to create a strong hypothesis for why cooperative hunting behaviors exist and how they evolved.

Citation: Lührs, M.-L., & Dammhahn, M. (2009). An unusual case of cooperative hunting in a solitary carnivore. Journal of Ethology, 28(2), 379–383. https://doi.org/10.1007/s10164-009-0190-8 

Torres Ortiz, S., Stedt, J., Midtiby, H. S., Egemose, H. D., & Wahlberg, M. (2021). Group hunting in harbour porpoises (Phocoena phocoena). Canadian Journal of Zoology, 99(6), 511–520. https://doi.org/10.1139/cjz-2020-0289

Contributor: Kyra Lockwood 

Researchers studied if harbor porpoises exhibit collaborative hunting behaviors when they are cooperating with one another. Collaborative hunting is a cooperative act that is very rarely seen in animals, yet it is associated with an increase in overall fitness. While collaborative hunting, one porpoises' actions are complementary to the other porpoises’ actions in order to improve the group’s success of feeding off of the prey resource. Previous research shows that animals who participate in cooperative hunting often have advanced cognitive abilities and social skills. The researchers in this study collected visual observations of harbor porpoises during their foraging events by using UAS, which is a type of drone. They hypothesized that most of the porpoises’ foraging events will occur with individual animals, and that foraging events with more than one animal will show unorganized behavior with no evidence of a structure between individuals. The results showed that group foraging events were much more common than individual foraging events in the porpoises. The group foraging data found that harbor porpoises hunt in groups significantly more often than they hunt individually. Observations reflected that when they foraged on a group of fish, the hunting strategy differed based on if they were by themselves or hunting within a group. This evidence shows that porpoise engages in collaborative hunting behavior which increases their fitness. 

The researchers in this article were studying cooperation and opportunism in Galapagos sea lions that hunt shoaling fish. It was observed that the sea lions had a core group that would lead the hunt, around 4-6, with opportunistic sea lions joining in near the end, usually 1-4. This core group usually includes females and opportunists are not apart of the main group. Their hunting strategy is to form a line, swim in zigzags, and lead the fish to a cove where they would be trapped. It is interesting that this species does this as they typically hunt alone when not utilizing this method. The researchers were able to learn this strategy by observing from the shore and taking pictures to further analyze afterwards. This was extremely helpful as they were able to gather much more information than if they had done this observational study without recording anything. It would have been beneficial to have used a wider scope lens as it would add precision to the animal count. They concluded that the core hunters of the group have a way of communicating about the goal prior to beginning the hunt, due to the fact that their movements are so synchronized. This study effectively proves that this species does cooperate, but it also brings up a lot of questions for future studies. One of the biggest questions I have now is how do these animals communicate with each other to be able to accomplish this shared goal? I also wonder what the social structure of sea lions is and who gets to be in this “core group” that gets all the fish.

Citation: De Roy, T., Espinoza, E. R., & Trillmich, F. (2021). Cooperation and opportunism in Galapagos sea lion hunting for shoaling fish. Ecology and Evolution, 11, 9206– 9216. https://doi.org/10.1002/ece3.7807