The quest to satisfy humanity’s increasing demand for space and resources has resulted in more than a few consequences for the natural world. One notable repercussion is the decline of various fauna populations. There are the tigers that are endangered due to hunting and habitat loss; the California condors that are critically endangered due to shooting and lead poisoning; and the gray wolves that were lost due to hunting from Yellowstone National Park for almost a century [1, 2, 3]. Conservationists have attempted to reverse declining trajectories through various management strategies. For apex predators, establishing protected sites and prohibiting hunting may allow populations to rebound; however, prey populations decline through not only human influences, but also the natural means of predation. Yet the ensuing protection of prey populations begs the question: does the protection of one population justify the removal of another?
Conservation is a term that has slight, technical differences in definition depending on whether the context is biological or ecological. For the purposes of this article, conservation is defined as the preservation of wildlife in the most efficient and economic manner. Population control strategies are often employed in conservation practices, especially with invasive species [4]. Removal of invasive species, although involving the extermination of a population, is justified on the basis of protecting vulnerable native species from non-native species that lack natural population restrictions. In the case of threatened or endangered prey species, however, native predators are exacerbating prey population declines [5]. Thus, the moral line of population control is blurrier. After all, the predators are also native species that are simply exhibiting normal behavior.
The moral line may become more distinct if evidence of significant success in predator management was presented. Unfortunately, the evidence has been inconclusive. Decision-making in conservation relies heavily on models predicting future outcomes. These models are incredibly helpful in visualizing even just a snippet of the complexities of population dynamics; however, they are also a bottomless pit of uncertainties. Some data cannot be collected due to ethical concerns, such as collecting teeth or other parts of an endangered species to gather relevant population data [6]. Insufficient data, therefore, requires very educated assumptions in order for models to work. Even if a convincing model is produced, every new day brings updated knowledge about the world around us, so models need to be constantly updated and revised. In short, models cannot capture everything and even vary between studies. Some studies suggest that removing predators would improve prey populations, while others suggest that removing predators does not change much at all [5, 7].
To better understand the complexities of population decline and the implementation of predator management plans, we can take a look at a popular conservation subject: the mountain caribou. Mountain caribou (Rangifer tarandus caribou) are ungulates, or hoofed mammals, that look very similar to reindeer and other members of the deer family [8]. Their range has significantly decreased over the years, such that they are only found in small pockets in the mountains of northeastern Washington, northern Idaho, and British Columbia [4, 9]. They live a fairly sedentary lifestyle, eating mainly lichens that grow on trees in the winter and some more diverse vegetation during warmer seasons [6, 8].
The caribou populations are declining as a consequence of habitat loss from deforestation, road construction, and wildfires [6]. These changes create an environment less suitable for caribou because it removes the trees on which lichen, one of their main food sources, grow. Instead, the resulting environment is more suited for other prey species like moose and deer that prefer areas with less trees and more shrubs [6]. As moose and deer populations increase, so do predator populations, namely wolves [4, 6]. Caribou also do not reproduce very quickly [8]. So, burdened by habitat loss and increased predation, the populations will continue to decline unless human intervention occurs.
Governments tend to choose predator management strategies because they are effective at addressing the issue while also being the most cost-effective option [4]. However, predator management is not without its difficulties. Not only is capturing the individuals incredibly labor and resource intensive, but the methods for capture raise even more ethical questions. In the case of wolves, one method of euthanasia was lacing bait with poison, which had the potential of affecting non-target species [4]. As for the question of whether removing the wolves at all is ethical, some justify the act by pointing out the resilience of wolf populations and the fact that when comparing mountain caribou and wolves, caribou populations are considered more threatened [4].
Alternatives to predator management include reducing other prey populations, which would lead to more “natural” declines in predator populations. This strategy, however, would raise ethical concerns similar to the ones for predator management, since another species would have to be sacrificed for the survival of the species of interest. Captive breeding programs are also an option, though they may silently encourage more habitat destruction [4]. With captive breeding programs as a “safety net” that will preserve endangered populations, less effort may be invested into addressing the root cause of population decline. Ideally, declining populations like the caribou should have their habitats protected and deforestation should be prohibited. In the end, the underlying issues regarding predator management and prey population declines all lead back to human intervention. Because of human influence, prey habitats are being disrupted, leading to population decline. Additionally, populations do not decline overnight; there have been gradual signs of decline [4]. However, conservation is a complicated field that involves not only the biological perspective, but also political and corporate interests. Thus, the chance of survival of many prey populations is not high, or at least will not be any time soon, as the influence of human civilization continues to spread.
Conservation strategies are not perfect solutions. The models used to inform management decisions and planning could be flawed, and there are external pressures from governments and industries that dictate which plans to enact. Even if predator management is successful in improving prey populations, this strategy ultimately does not solve the underlying cause of their decline. The declining caribou populations, as with many prey populations, are due to human activities. Predator management, therefore, may be a last resort, but cannot be justified as a means of benefiting an endangered prey population if it is the sole action taken.
References:
1. WWF-Canada. (2021, April 30). Tigers: Endangered Species Facts, info & more. WWF.CA. https://wwf.ca/species/tigers/.
2. U.S. Department of the Interior. (2017). California condor reintroduction & recovery. National Parks Service. https://www.nps.gov/articles/california-condor-recovery.htm.e.
3. National Geographic Society. (n.d.). Wolves of Yellowstone. National Geographic Education. https://education.nationalgeographic.org/resource/wolves-yellowstone/ 4. Johnson, C. J., Ray, J. C., & St‐Laurent, M. (2022). Efficacy and ethics of intensive predator management to save endangered Caribou. Conservation Science and Practice, 4(7). https://doi.org/10.1111/csp2.12729.
5. Schneider, M. F. (2001). Habitat loss, fragmentation and predator impact: Spatial implications for prey conservation. Journal of Applied Ecology, 38(4), 720–735. https://doi.org/10.1046/j.1365-2664.2001.00642.x
6. Wittmer, H. U., Ahrens, R. N. M., & McLellan, B. N. (2010). Viability of mountain caribou in British Columbia, Canada: Effects of habitat change and population density. Biological Conservation, 143(1), 86–93. https://doi.org/10.1016/j.biocon.2009.09.007
7. Grafton, R. Q., & Silva-Echenique, J. (1997). How to manage nature? strategies, predator-prey models, and Chaos. Marine Resource Economics, 12(2), 127–143. https://doi.org/10.1086/mre.12.2.42629190
8. Center for Biological Diversity. (n.d.). Natural History. Natural history. https://www.biologicaldiversity.org/species/mammals/woodland_caribou/natural_history. html
9. Ray, J. C., Cichowski, D. B., St-Laurent, M.-H., Johnson, C. J., Petersen, S. D., & Thompson, I. D. (2015). Conservation status of caribou in the Western Mountains of canada: Protections under the Species at Risk Act, 2002-2014. Rangifer, 35(2), 49. https://doi.org/10.7557/2.35.2.3647