Social hierarchies are endlessly fascinating structures. We watch them play out on TV in everything from Bridgerton to Big Brother, from Game of Thrones to House of Cards. Across cultures and all throughout history people have competed in the endless struggle for social superiority, bringing access to wealth and prestige, a quality spouse and a secure home to raise the next generation.
It’s not unique to humanity! We see the same dynamics playing out across the animal kingdom. An interesting article in The Conversation recently looked at the way social dominance impacts populations of native mammals in Australia, particularly in stick-nest rats. Social hierarchies have a very real impact on our feral rabbits too, which I will explain here based on our work at Turretfield in South Australia where my colleagues have trapped rabbits for over 25 years and where I used DNA sequencing to explore the familial relationships of rabbits across numerous warrens. I’m also drawing on the findings of Heiko Rödel, Dietrich von Holst and their colleagues who studied rabbits in a large enclosure in Germany over many years.
Social hierarchies in rabbits are not so unlike what you would find in a period drama. Each warren is like a grand manor house, occupied by a number of females who are usually related. Perhaps a mother and her daughters, plus a grandmother matriarch and an aunt and a cousin. These females have their own internal hierarchy, in which the strongest have access to the safest feeding areas and best nesting burrows. Subordinate females are routinely harassed, have less access to quality food and must nest in peripheral burrows. As you can imagine, the stress of all this makes subordinates more prone to disease, malnutrition and predation. Their survival and that of their kittens is much reduced compared to dominant females.
Male rabbits have their own social ladder, which is if anything more vicious. As juvenile males mature the dominant males becoming increasingly less tolerant of their presence and they begin to roam further afield, risking predators to scout neighbouring warrens in search of a new home full of good prospective women. Any given warren will be home to a small handful of generally unrelated males, depending on its size. That being said, access to mates is not equitable. The most eligible bachelor, the dominant male, gets access to whichever female he desires – which is probably best summarised as all of them! That includes, of course, the dominant female who is the most likely to be successful at producing offspring that survive the rigours of kittenhood – juvenile mortality can be over 90%. Not all is lost for the subordinate males. Sometimes they do get lucky, either in their home warren or while visiting a neighbouring warren. Perhaps it’s a matter of being in the right place at the right time to sneak past the dominant male and claim first dibs.
The upshot of all these social machinations is an ingenious way to give the next generation a genetic advantage. The fittest animals become dominant and produce by far the most offspring, while the risks of inbreeding are neatly sidestepped by having the boys leave home while the girls mostly stay.
Does this affect us in our quest for a rabbit-free Australia? Well, it might. We know that the dominant pair produce most of the surviving offspring. If those dominant rabbits carry genes for genetic resistance to RHDV then most of the next generation will inherit those genes, which is the last thing we want. That’s a good incentive to go hunt down the adult survivors after an outbreak!
Rödel, H., A. Bora, J. Kaiser, P. Kaetzke, M. Khaschei and D. von Holst (2004). “Density‐dependent reproduction in the European rabbit: a consequence of individual response and age‐dependent reproductive performance.” Oikos 104(3): 529-539.
Rödel, H. G., D. von Holst and C. Kraus (2009). “Family legacies: short‐and long‐term fitness consequences of early‐life conditions in female European rabbits.” Journal of Animal Ecology 78(4): 789-797.
von Holst, D., H. Hutzelmeyer, P. Kaetzke, M. Khaschei, H. G. Rödel and H. Schrutka (2002). “Social rank, fecundity and lifetime reproductive success in wild European rabbits (Oryctolagus cuniculus).” Behavioral Ecology and Sociobiology 51(3): 245-254.
von Holst, D., H. Hutzelmeyer, P. Kaetzke, M. Khaschei and R. Schönheiter (1999). “Social rank, stress, fitness, and life expectancy in wild rabbits.” Naturwissenschaften 86: 388-393.
Wells, K., P. Cassey, R. G. Sinclair, G. J. Mutze, D. E. Peacock, R. C. Lacy, B. D. Cooke, R. B. O’Hara, B. W. Brook and D. A. Fordham (2016). “Targeting season and age for optimizing control of invasive rabbits.” The Journal of Wildlife Management 80(6): 990-999.