The Development of Social Behavior in Three South American Canids
Here’s a neat paper from 1983.
The bush dog, crab-eating fox, and maned wolf are three species of canids from South America. The maned wolf is mostly solitary, with contact between males and females restricted to the breeding season and pup-rearing. Crab-eating foxes, by contrast, pair up and maintain territories together. Pups also sometimes remain with their parents past reproductive age, depending on territory availability.
Of all three species, the bush dog is the most social, living in packs much like the gray wolf or African wild dog does. This enables them to work together and kill prey much larger than themselves, like capybara.
At the time, these three species were all placed within the South American branch of Canidae, distinct from the true foxes and the true dogs. (This has since been challenged.*) The paper’s author, Maxeen Biben, chose to compare them because they had such a range of different social lifestyles.
Since the bush dog was the most social of the three, she expected it to show the most complex social development; likewise, she thought the maned wolf would have the least, and the crab-eating fox would be somewhere in between. However, some of her results were rather surprising.
This paper is extremely detailed, so I’ll try to sum up the gist of the results. I highly recommend you read through it yourself, though.
- Crab-eating foxes developed specific social behaviors about a week before the other two species.
- Bush dog puppies played together more often, cooperated in object play more often, and rested together for longer than the other two species.
- They also did not defend food items, while the other two species did.
- However, crab-eating foxes and maned wolves showed more complex social interactions and some social behaviors that the bush dogs did not (such as play-bows and grappling).
- Bush dog pups also bit one another and vocalized more frequently than the other two, making their interactions appear very aggressive. However, this aggression was brief and did not affect relationships in the long term.**
- There were no discernible sex differences in social development.
- There was no evidence of a specific dominance hierarchy forming in any of the groups of pups. All pups behaved submissively towards their parents.
Taken together, the results allowed Biben to reach some extremely interesting conclusions.
Given that maned wolves are much larger than crab-eating foxes, it is not surprising that their development lagged behind (larger size = slower growing). But considering the fact that bush dogs are about the same size as crab-eating foxes, it is surprising that their social development was slower.
Biben suggests that this is because the bush dogs are more neotonized than either of the other two species. The extension of a growth and play period is very common in the evolution of highly social species. Bush dogs even have a more paedomorphic appearance, with their rounded heads and short, stocky bodies.
The lack of more complex social behavior in bush dogs was also unexpected, but Biben theorizes that this is because bush dogs experience less conflict with members of their own species than the more solitary and territorial species do. They may need fewer signals to avoid fighting.
Biben also points out that bush dog pups had a higher incidence of submissive behavior (rolling over) which is important in maintaining a lack of aggression in large social groups.***
Finally, the lack of a discernible social hierarchy between pups of any species led Biben to criticize some earlier studies suggesting that canids such as foxes, wolves, and coyotes form dominance hierarchies as pups. She suggests that the reason these studies came up with these results is that they were carried out on captive animals that were removed from their parents or each other for long periods of time, disrupting their normal social development.
While all the litters in this study were also in captivity, they were kept together with both parents. Biben concludes that the normative social structure of canids is simply that pups are submissive to their parents and that they develop no consistent hierarchy within their litter.
Biben, M. (1983). Comparative ontogeny of social behaviour in three South American canids, the maned wolf, crab-eating fox and bush dog: implications for sociality. Animal Behaviour, 31(3), 814-826.
Image credit: Tambako the Jaguar
*In some more recent phylogenies, the bush dog is placed with tribe Canini near the African wild dog. (x)
**Other authors have suggested that the bush dog’s high frequency of vocalization and apparent aggression stems from the fact that they have less mobile faces and bodies to communicate with than other canine species. Bush dog vocalizations are quite complex. (x, x)
***Some other highly social canid species, like African wild dogs, have been observed to ‘gang up’ on a single individual within the group. Biben suggests that this may be a form of submission to the group by the individual that rolls over, but it could also be a form of group hunting play where one member inadvertently becomes the ‘victim.’ (x)