Abstract
Large carnivores inhabiting ecosystems with heterogeneously distributed environmental resources with strong seasonal variations frequently employ opportunistic foraging strategies, often typified by seasonal switches in diet. In semi-arid ecosystems, herbivore distribution is generally more homogeneous in the wet season, when surface water is abundant, than in the dry season when only permanent sources remain. Here, we investigate the seasonal contribution of the different herbivore species, prey preference and distribution of kills (i.e. feeding locations) of African lions in Hwange National Park, Zimbabwe, a semi-arid African savanna structured by artificial waterholes. We used data from 245 kills and 74 faecal samples. Buffalo consistently emerged as the most frequently utilised prey in all seasons by both male (56%) and female (33%) lions, contributing the most to lion dietary biomass. Jacobs’ index also revealed that buffalo was the most intensively selected species throughout the year. For female lions, kudu and to a lesser extent the group “medium Bovidae” are the most important secondary prey. This study revealed seasonal patterns in secondary prey consumption by female lions partly based on prey ecology with browsers, such as giraffe and kudu, mainly consumed in the early dry season, and grazers, such as zebra and suids, contributing more to female diet in the late dry season. Further, it revealed the opportunistic hunting behaviour of lions for prey as diverse as elephants and mice, with elephants taken mostly as juveniles at the end of the dry season during droughts. Jacobs’ index finally revealed a very strong preference for kills within 2 km from a waterhole for all prey species, except small antelopes, in all seasons. This suggested that surface-water resources form passive traps and contribute to the structuring of lion foraging behaviour.
Highlights
Quantifying predator diets is an essential step to understand predator ecology, and the influence that predators have on their prey populations [1,2]
Kill investigation to study carnivore diet is biased towards larger species that are easier to detect using GPS data since predators will stay longer at a the kill of a larger prey animal, and using carcasses alone clearly underestimates the number of feeding events on small species, sometimes up to 50% [3,4]
We used a combination of the two approaches to provide the most complete description of lion diet in Hwange National Park, an approach that has already proved very useful for large carnivore diet in other systems [3,4,38]
Summary
Quantifying predator diets is an essential step to understand predator ecology, and the influence that predators have on their prey populations [1,2]. Across-ecosystems, comparisons of large mammalian carnivore diet have provided a good understanding of the preferred prey weight range of several carnivore species [6,7,8], but local studies are still needed to unravel the role of environmental factors and prey availability. Semi-arid ecosystems are characterized by seasonal variations in surface-water and vegetation resources, with several implications for herbivores, and their predators. In African semi-arid savannas, surface-water is a heterogeneously distributed, limiting resource which becomes scarcer as the dry season progresses. The regular need to access drinking water constrains the movement of herbivores, and their distribution in the dry season [9,10,11,12]. Seasonal surface-water dynamics influences the probability which predators can find prey and is likely to have several consequences for the ecology of predator-prey interactions
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