By Sze-Wing Yiu, Postdoctoral Fellow
Reintroduction is a conservation practice that has been applied to re-establish species in areas where they had been extirpated. In South Africa, large carnivores are being introduced increasingly to wildlife reserves as tourist attractions. Post-release monitoring is critical for successful reintroductions and includes two major aspects: 1) how the reintroduced animals adapt to the new environment, and 2) the influence of the reintroduction on species interactions, which is particularly important for large carnivores due to their influence on predator-prey dynamics.
During my PhD study from 2011 to 2015, I investigated the movement and habitat use of lions introduced to Dinokeng Game Reserve and the impact of the reintroductions on prey vigilance behaviour. Eleven lions were introduced and fitted with satellite collars that recorded their GPS locations six times per day at regular intervals. Using these data, I analysed changes in rates of movement, home range establishment and selection for different habitat features over time. Results revealed that the order and location of release have a great influence on the behaviour of the lions. The lions continued to expand their home ranges throughout the study period, but the locations of home ranges remained within the areas of their releases. Lions released at a later stage had smaller home ranges than those released earlier and showed a selection for suboptimal resources while those released earlier selected for favourable resources. Lions released earlier have the advantage to explore in a competitor-free environment while those released later have to be cautious of the already established lions to avoid territorial conflicts.
To understand the behavioural responses of prey to the reintroduction of lions, I observed zebras and wildebeests in the field, and recorded and compared the duration of their vigilance behaviour between high and low predation risk areas. The two prey species responded to lions differently, with zebras increasing their vigilance behaviour in high predation risk area, and wildebeests doing the opposite. Large predators were absent from the reserve for over a century before lion reintroductions. It is possible that more time is required for wildebeests to learn the predation risks than for zebra, resulting in the differences in their responses. Wildebeests might also rely more on other anti-predatory behaviour, e.g. they form larger herds than zebra, in response to predators, resulting in less sensitive response in their vigilance behaviour.
My study suggests the importance of identifying suitable release sites and maximizing the space between successive reintroductions of large carnivores, such that the reintroduced animals have greater chances to acquire favourable resources under reduced pressure from competitors at early stages of release. Monitoring of the behavioural responses of different prey species is also critical to understand the influence of large carnivore reintroductions and preventing adverse effect of the reintroductions on prey populations.
To expand my research on large carnivores movement behaviour, my postdoctoral research aims to understand the movement patterns of lions in response to prey movement and distribution in the Kruger National Park, by using different modelling techniques. Keep an eye on this blog if you are interested in my research! I will also be giving a talk on my study at the Cape Union Mart, Eastgate Mall on 16 August 2018 from 18:30 to 19:30!