Abstract
Tanzania's Ruaha landscape is an international priority area for large carnivores, supporting over 10% of the world's lions and important populations of leopards and spotted hyaenas. However, lack of ecological data on large carnivore distribution and habitat use hinders the development of effective carnivore conservation strategies in this critical landscape. Therefore, the study aimed to (i) identify the most significant ecogeographical variables influencing the potential distribution of lions, leopards and spotted hyaenas across the Ruaha landscape; (ii) identify zones with highest suitability for harbouring those species; and (iii) use species distribution modelling algorithms (SDMs) to define important areas for conservation of large carnivores. Habitat suitability was calculated based on environmental features from georeferenced presence-only carnivore location data. Potential distribution of large carnivores appeared to be strongly influenced by water availability; highly suitable areas were situated close to rivers and experienced above average annual precipitation. Net primary productivity and tree cover also exerted some influence on habitat suitability. All three species showed relatively narrow niche breadth and low tolerance to changes in habitat characteristics. From 21,050 km2 assessed, 8.1% (1,702 km2) emerged as highly suitable for all three large carnivores collectively. Of that area, 95.4% (1,624 km2) was located within 30 km of the Park-village border, raising concerns about human-carnivore conflict. This was of particular concern for spotted hyaenas, as they were located significantly closer to the Park boundary than lions and leopards. This study provides the first map of potential carnivore distribution across the globally important Ruaha landscape, and demonstrates that SDMs can be effective for understanding large carnivore habitat requirements in poorly sampled areas. This approach could have relevance for many other important wildlife areas that only have limited, haphazard presence-only data, but which urgently require strategic conservation planning.
Highlights
Apex predators such as lions (Panthera leo), leopards (Panthera pardus) and spotted hyaenas (Crocuta crocuta) play an important role in the regulation of ecological interactions and ecosystem health, substantially influencing lower trophic levels [1,2]
Large carnivore distribution and habitat selection is largely determined by prey availability [22,23], which in turn is affected by factors such as vegetation cover, water availability and elevation [23,24,25]
The majority of carnivore location points considered for the models were collected within Ruaha National Park (RNP), with a total of 96% (n = 117) of the leopard points collected in RNP, 97.9% (n = 91) of the locations for spotted hyaenas, and 88.1% (n = 52) for lions, with the remainder collected outside the park
Summary
Apex predators such as lions (Panthera leo), leopards (Panthera pardus) and spotted hyaenas (Crocuta crocuta) play an important role in the regulation of ecological interactions and ecosystem health, substantially influencing lower trophic levels [1,2]. As keystone species [3,4,5], they affect the density of mesopredators and natural prey [5,6], and influence plant communities [7] by suppressing the effects of large ungulates on vegetation [8,9,10] Their removal from the ecosystem can unleash trophic cascades [11], resulting in alteration of top-down regulations of the ecosystem [8,12] and loss of biodiversity and species richness [12,13]. In many high-priority wildlife areas, researchers lack the time and resources needed to collect systematic presence-absence data on prey and carnivore distributions at the landscape level They often rely upon opportunistic detections of species occurrence, and this presenceonly data might not be well-suited to commonly-used techniques such as occupancy modelling [26,27]
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