Apparent competition, lion predation, and managed livestock grazing: can conservation value be enhanced?

Authors: NG'WENO, CAROLINE - University Of Wyoming; BUSKIRK, STEVEN - University Of Wyoming; GEORGIADIS, NICHOLAS - Puget Sound Institute; GITUKU, BENARD - Oi Pejeta Conservancy; KIBUNGEI, ALFRED - Oi Pejeta Conservancy; Porensky, Lauren; RUBENSTEIN, DANIEL - Princeton University; GOHEEN, JACOB - University Of Wyoming

Submitted to: Frontiers in Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2019
Publication Date: 4/12/2019
Citation: Ng'Weno, C.C., Buskirk, S.W., Georgiadis, N.J., Gituku, B., Kibungei, A.K., Porensky, L.M., Rubenstein, D.I., Goheen, J.R. 2019. Apparent competition, lion predation, and managed livestock grazing: can conservation value be enhanced? Frontiers in Ecology and Evolution. 7:123. https://doi.org/10.3389/fevo.2019.00123.
DOI: https://doi.org/10.3389/fevo.2019.00123

Interpretive Summary: In rangeland ecosystems, predator restorations can shift pressures on co-occurring prey species. In some cases, a primary prey species can support large predator populations that then cause increased pressure on other, more preferred prey species--this phenomenon is called apparent competition. We asked whether apparent competition reorganized prey communities following restoration of lions to a semiarid savanna. We also asked how livestock production might alter interactions between lions and their prey. Three lines of evidence indicated that Jackson’s hartebeest, an ungulate of conservation concern, are suppressed via lion-mediated apparent competition. First, hartebeest populations tended to decline where they were exposed to lions, but displayed population growth where they were protected from lions. Second, spatial overlap between plains zebra (the primary prey of lions) and hartebeest further exacerbated lion predation on hartebeest. Finally, hartebeest were killed selectively by lions, whereas lions showed no selective preference for zebra. We then tested whether glades (nutrient-rich hotspots created by abandoned cattle corrals) could be used to influence lion predation on hartebeest. We found that because zebra (but not hartebeest) aggregate in and around glades, proactive cattle management can be used to manipulate the spatial distribution of zebra on the landscape and, in turn, the hunting activity of lions. Survival of hartebeest increased with increasing distance from glades. Thus, by positioning corrals away from hartebeest territories, livestock management can be used to “pull” lions away from this declining species. Our findings demonstrate how informed placement of livestock corrals can be used to improve conservation outcomes in multiple-use landscapes.

Technical Abstract: Predator restorations often result in apparent competition, where co-occurring prey populations experience asymmetric predation pressure driven by predator preferences. In many rangeland ecosystems, livestock share the landscape with wildlife, including ungulates and the large carnivores that consume them. We examined whether apparent competition reorganized prey communities following restoration of lions (Panthera leo) to a semiarid savanna, and whether and how livestock production could alter this indirect interaction between lions and their prey. Three lines of evidence supported the hypothesis that Jackson’s hartebeest (Alcelaphus bucelaphus lelwel; an ungulate of conservation concern) are suppressed via lion-mediated apparent competition. First, hartebeest exhibited an Allee effect where they were exposed to lions, but displayed negative density-dependent population growth where they were protected from lions. Second, spatial overlap between plains zebra (Equus burchelli; the primary prey of lions) and hartebeest further exacerbated lion predation on hartebeest. Finally, hartebeest were killed selectively by lions, whereas zebra were killed by lions in proportion to their abundance. We then tested whether glades (nutrient-rich hotspots created by abandoned cattle [Bos indicus] corrals) could be used to manipulate top-down control of hartebeest via their influence on the spatial distribution of zebra. Zebra aggregated at glades, and survival of hartebeest increased with increasing distance from glades, suggesting that corrals may be placed on the landscape away from hartebeest to create spatial refuges from lions. Our findings demonstrate how informed placement of livestock corrals can be used to manipulate the spatial distribution of primary prey (zebra), thereby reducing apparent competition suffered by hartebeest. Our work further provides an example of how integrating apparent competition theory with proactive livestock production can improve conservation efforts in multiple-use landscapes.