A pride of lionesses forms a beautifully-coordinated trap, chasing a giraffe into what appears to be inevitable death; unexpectedly, the hunt ends in failure as the giraffe viciously tramples the lead female and escapes relatively unscathed. David Attenborough states that lion hunts have the highest rate of failure in the desert, which is not surprising given the characteristically harsh conditions.
If lion hunts in the desert have the highest rates of failure, how do prides still manage to survive within that ecosystem?
One consideration is the size of the lion pride relative to prey abundance. Across ecological systems, there is evidence that an ideal ratio of prey to predators is 3:1 [1]. Although larger lion group sizes may increase the probability of a successful hunt, there is a significant tradeoff in the number of mouths to feed. As a result, the optimal group size depends on the context. In the case of harsher environmental conditions, optimal group size is limited to around three to six females [2].
Another adaptation is the evolution of cooperative hunting strategies in response to the arid desert, where prey is more interspersed and ambush is not possible [3]. The lion has an overall hunt success of just 15% in the desert, but when working in groups lionesses are 25% more likely to have a successful hunt [3]. Their group strategy includes two main components: 1) ‘wings’, lions who circle the prey on either side, and 2) the ‘center’, typically a larger, older female who waits in a position where she is able to catch prey fleeing from the wings [3].
So, what are the males of the pride doing while the females hunt in groups? Male lions are thought to be less successful than females in hunting since they hunt alone. In reality, data suggests that males are just as successful as females in savannas [4]. Males are more likely to attack prey by ambush, which requires dense vegetation [4]. Ambush hunting in lions has a success rate of about 70% [3]. In the arid desert, there is no dense vegetation, nullifying the strategy in preference of female cooperation.
What does this tell us about sticking together? Well, perhaps we all have something to gain by helping our peers!
by Veronica Chiu, Zach Harrison & Christina Hong
Planet Earth II, Episode 4: Deserts, starting at approximately 5:20.
References
- Hatton, I, KS McCann, KM Fryxell, TJ Davies, M Smerlak, ARE Sinclair, & M Loreau. 2015. The predator-prey power law: biomass scaling across terrestrial and aquatic biomes. Science 349: 1-12.
- VanderWaal, KL, Mosser, A & C Packer. 2009. Optimal group size, dispersal decisions and postdispersal relationships in female African lions. Animal Behaviour 77: 949-954.
- Stander, PE. 1992. Cooperative hunting in lions: the role of the individual. Behavioral Ecology and Sociobiology 29.6: 445-454.
- Loarie, SR, Tambling, CJ & GP Asner. 2013. Lion hunting behaviour and vegetation structure in an African savanna. Animal Behaviour 85: 899-906.
The Evolution of Planet Earth 