Humans, Predators and Prey

Large mammals shape their environment and are of great importance to the tourism and conservation industry. Our research provides invaluable information to help manage both wild and captive populations. Here are a few examples of some of the work that has been produced over the last year:

Lion conservation is a complicated problem

Lions are apex predators, experience multiple threats due to human activity and are classified as vulnerable (IUCN Red List). Analysis by Peter Lindsey and co-authors teaches us more about these effects on their distribution and numbers. Eleven threats were identified in total, with human-lion conflict and depleted food supply (resulting from the bushmeat trade) emerging as the top threats. Lion conservation is a complicated problem, with many threats interacting simultaneously. The devastating effect of this can easily result in the complete eradication of a lion population. A problem tree and root-cause analysis was used in order to visualise this complex situation. The results of this study will aid conservation managers, social scientists and politicians in teasing apart the underlying issues before lion conservation can be tackled efficiently.

Vigilance is more than just looking out for danger

In zoological terms, vigilance is more than looking out for danger, it is also observing what other animals are doing around you (social vigilance). A study on impala by Anita van Deventer and Adrian Shrader investigated circumstances under which individuals within a herd prioritise different behaviour. Social vigilance involves watching to see if other animals are alarmed, and where they are feeding, for example, and if an impala is to survive, it must find the right balance between foraging and avoiding predators. Herd size was predictably greater in areas where predator numbers and density were higher. However, what was surprising was that impala in the middle of the herd reduced their antipredator vigilance and increased their social vigilance, but didn’t increase overall vigilance. In contrast, animals at the edges increased both social and antipredator vigilance, and also proportionally increased their antipredator vigilance. This demonstrates that centrally positioned impala are advantaged because they have more time to forage, or find better forage, in addition to the reduced risk of predation due to safety in numbers. Interestingly, impala in predator-free areas showed the same amount of vigilance regardless of herd position, but still exhibited high levels of total vigilance, despite the reduced threat.

Intense vigilance was lower outside lion home ranges

In another paper on vigilance, Mark Keith and colleagues looked at predation risk in relation to intense and routine vigilance in Burchell’s zebra and blue wildebeest. Both species form an important part of lion diet. Intense vigilance is when the environment is scanned continuously, and all other activity stops, while routine vigilance is when the animal continues to chew whilst looking out for predators. The relationship between these two behaviours was calculated and found to be inversely proportional. Zebra’s intense vigilance was lower outside lion home ranges, and their routine vigilance was higher in herds. The intense vigilance of wildebeest decreased with an increase in herd size and increased with the presence of a calf. Wildebeest differed from zebra showing similar vigilance in- and outside lion home ranges, but when grass was tall then intense vigilance increased due to the perceived higher ambush risk. Intense vigilance also increased with a higher tree density but, interestingly, decreased at a certain threshold, probably because wildebeest benefited from added tree cover. Wildebeest relied more on safety in numbers than zebra in order to avoid predation.

This article was originally published in the University of Pretoria’s Faculty of Natural and Agricultural Sciences’ newsletter. Follow this link to read some more articles https://bit.ly/3yd2xeT

References

Bauer H, Dickman A, Chapron G, Oriol-Cotterill A, Nicholson SK, Sillero-Zubiri C, Hunter L, Lindsey P, Macdonald DW. 2020. Threat analysis for more effective lion conservation. Oryx.:1-8.

van Deventer A, Shrader AM. Predation risk and herd position influence the proportional use of antipredator and social vigilance by impala. Animal Behaviour. 2021 Feb 1;172:9-16.

Yiu SW, Keith M, Karczmarski L, Parrini F. Predation risk effects on intense and routine vigilance of Burchell's zebra and blue wildebeest. Animal Behaviour. 2021 Mar 1;173:159-68.

Meredith Thornton

Science Communicator