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Editor’s Choice – Predators also live in landscapes of fear

February 2012 (Issue 49:1)

Valeix, M., Hemson, G., Loveridge, A.J., Mills, M.G.L. & Macdonald, D.W. (2012) Behavioural adjustments of a large carnivore to access secondary prey in a human-dominated landscape. Journal of Applied Ecology, 49, 1365-2664

There is a growing awareness among ecologists that the risk of predation imposes a powerful control over the use of habitats by prey animals, often over-riding the attractions of resource-rich hotspots. For any wild animal to survive long enough to reproduce successfully requires that it perceives spatial variations in its environment and adapts its behavior accordingly. In cognitive animals this results in ‘layers’ of spatial information being processed simultaneously, with each layer relating to a factor such as food, water, predation risk, mating opportunities, terrain, thermal cover, etc. In effect, each layer distorts the way in which the environment is perceived depending on the relative strength of each factor’s influence on an animal’s fitness at any one time. If predation risk is a significant factor then the animal perceives its environment as a “landscape of fear” (Laundré, Hernández & Altendorf 2001) and adjusts its activity and use of habitats accordingly. This concept has attracted particular attention in the past decade or two as efforts to conserve and restore large predator populations – such as wolves in Yellowstone – have become viewed in the context of trophic cascades. While the links and mechanisms involved in such cascades need further study (Creel & Christianson 2009), it is now well recognized that predators can impose strong top-down controls on ecosystems. What is less recognized is that even top predators live in landscapes of fear too, which is why we selected for this Issue’s Editor’s Choice an article on African lions living in fear of people.

Using GPS telemetry on resident lions in the highly seasonal ecosystem that includes the Makgadikgadi Pans of central Botswana, Valeix et al. found these lions to switch prey and change hunting behavior between seasons. In the wet season, when migratory wild ungulates are abundant, lions preferentially exploit this prey base and keep their distance from human settlements. But in the dry season, when the migratory wild ungulates move away, the lions are unable to follow because they cannot leave their cubs and territories undefended. Then they switch to preying on the low density of resident wild ungulates and, most crucially, cattle. The cattle are watered at ‘cattle posts’, where herders have firearms and are likely to shoot at any lions they encounter, and so lions steer clear of those locations by day when herders are active. Lions might pass by at night, but then they speed up their movement until they are >1 km away, and generally kill cattle 4-5 km from cattle posts so they have time to feed without risk of retaliation by herders. Key findings are that lions learn to fear and avoid people, even at cattle posts where easy prey is abundant, and so livestock depredation is most common where herders allow stragglers to roam far from protection at night. Also, livestock depredation is seasonal, occurring mainly when migratory prey leave and resident prey is inadequate.

The Makgadikgadi cattle herders and lions exemplify the human-wildlife conflict that has existed ever since livestock domestication began. Now, however, with advanced weapons and poisons, expanding human and livestock populations, and reduced indigenous prey abundances, humans have virtually eradicated large predators - and big cats in particular – from the world’s rangelands. Yet studies such as this one by Valeix et al. show there could be smarter ways of mitigating the conflict. Manipulating predators’ landscapes of fear by introducing disruptive and aversive stimuli is clearly an option (Shivik 2006). Managing livestock depredation at a level that compensation schemes can cope with could involve monitoring predator densities (Durant et al. 2011; Karanth et al. 2011) and applying non-lethal measures (e.g. fertility control) if possible. If selected individuals have to be removed from the predator population then their killing, if done strategically, should enhance the landscapes of fear perceived by the survivors. Such efforts are costly but they might only be needed in the times of year when prey-switching occurs. Also, if the behavior of the predators can be manipulated then the same should apply to the herders and their livestock. Herders need incentives to be more diligent during periods when depredation is most likely and keep their livestock within the zones that predators are induced to avoid. Livestock need to be allowed to develop their own landscapes of fear, which is impossible for the continually mixed and moved herds on public rangelands in the western USA, for example, where depredation by wolves is an increasingly contentious issue. Finally, the indigenous prey base has to be conserved or else large predators will have no future anyway.

There are few issues in conservation practice around which opinions are more polarized than the existence of large carnivores in the matrix between protected areas. As applied ecologists our credibility depends on objective reporting of our research into such issues, leading to pragmatic, science-based solutions. This Editor’s Choice, which is a good example of such a report, adds to the mounting evidence that fear – not only in prey animals but also in their predators – is a phenomenon that smart managers could make more use of in mitigating human-wildlife conflict.

Johan T. du Toit

johan.dutoit@usu.edu

Reference

Creel, S. & Christianson, D. (2009) Wolf presence and increased willow consumption by Yellowstone elk: implications for trophic cascades. Ecology, 90, 2454–2466.
Durant, S.M., Craft, M.E., Hilborn, R., Bashir, S., Hando, J. & Thomas, L. (2011) Long-terms trends in carnivore abundance using distance sampling in Serengeti National Park, Tanzania. Journal of Applied Ecology, 48, 1490-1500.
Karanth, K.U., Gopalaswamy, A.M., Kumar, N.S., Vaidyanathan, S., Nichols, J.D. & MacKenzie, D.I. (2011) Monitoring carnivore populations at the landscape scale: occupancy modeling of tigers from sign surveys. Journal of Applied Ecology, 48, 1048-1056.
Laundré, J.W., Hernández, L. & Altendorf, K.B. (2001) Wolves, elk, and bison: re-establishing the “landscape of fear” in Yellowstone National Park, USA. Canadian Journal of Zoology, 79, 1401-1409.
Shivik, J.A. (2006) Tools for the edge: what’s new for conserving carnivores. BioScience, 56, 253-259.