Trophy Hunting Harms Grizzly Bears
For the first time in over 40 years, Yellowstone’s grizzly bears will be subjected to trophy hunting. Hunting was ended back in 1975 with institution of Endangered Species Act protections, but aggressively resurrected by wildlife managers the moment those protections were removed during fall of 2017 and management authority turned over by the federal government to the states.
Wyoming is positioning itself to be the main perpetrator of hunting, although Idaho, every bit as regressive, is rapidly catching up. These states are billing their hunting plans as “conservative,” which is simply bald-face propaganda. I wrote recently about the more immediate and prospective population-level impacts of state management plans. The unabashed goal is population reduction, not maintenance, and because of inane provisions, males will be slaughtered. But these more direct numeric effects will be predictably magnified longer-term by indirect effects caused by changes in bear behavior. However, for insight into these effects, we need to turn to research being produced by (surprise, surprise) progressive Scandinavian scientists rather than our local researchers slaved to a political agenda.
A Swedish research team has been pumping out publications during the last 10+ years of direct relevance to assessing the indirect impacts of trophy hunting on brown and grizzly bears—all of the same species, Ursus arctos. A sampling of these recent publications includes Bishof et al. (2009, 2018), Zedrosser et al. (2013), Steyaert et al. (2013, 2014), Gosselin et al. (2015, 2017), Leclerc et al. (2017), Frank et al. (2017, 2018), and Van de Walle et al. (2018).
But the legacy of this research dates back to 1997 when Jon Swenson published a paper in Nature reporting on infanticide by male bears rooted in social disruptions caused by hunting. Of parenthetical interest, Jon Swenson, who functions as a sort of Godfather for this research team, was once an employee of Montana Fish, Wildlife and Parks before emigrating to Sweden to complete a doctoral degree focused on hazel grouse. Grouse somehow led him to brown bears.
In any case, this corpus of Scandinavian research is readily extrapolated to our North American variants of brown bears, including grizzly bears in the northern Rockies, which is especially relevant at this juncture given the current lethal regime and related hunting plans being promulgated by the states of Wyoming and Idaho. However, implications for management of grizzlies in our part of the world may be somewhat obscure, especially for those who aren’t particularly interested in penetrating the veil of scientific jargon. So, very briefly, here’s my take:
Hunting Jeopardizes Bear Populations Near-Term
Hunting of bears, along with other forms of human-caused mortality targeting adult males, often leads to increased killing of cubs by surviving males. Reasonably enough, this begs the question, Why?
Increases in cub-killing follow indirectly from the fact that there is intense competition for breeding opportunities among adult males. A three-year reproductive cycle among females means there are 2-3 males trying to mate with any single female, which escalates competition among males to a fevered pitch. If a dominant resident male is killed, there are numerous other males ready to step in and, as means of enhancing their reproductive success, kill the cubs produced by the deceased male as means of accelerating the onset of estrus among neighborhood females. Such behavior is relatively common among carnivores, including among African lions (for example, Loveridge et al. 2007).
This social mayhem can additionally disrupt use of space and efficiencies of foraging by reproductive females with potential nutritional consequences and derivative negative impacts on female reproductive success. Such nutritional effects on female fecundity predictably exacerbate the more overt direct and indirect effects of hunting on survival of adult males and dependent young.
The upshot is that hunting can cause unintended unanticipated indirect and negative near- and long-term effects on growth of brown/grizzly bear populations. The Scandinavian research team has impeccably documented all the behavioral and demographic links in this causal chain, which means that there is minimal arm-waving behind this over-arching conclusion.
Of relevance to the northern Rockies, we can expect much the same consequences from any human-caused mortality that disproportionately targets adult males—as with the trophy hunting being proposed by Idaho and Wyoming, exacerbating a regime that is already excessively lethal to male bears.
Hunting Jeopardizes the Very Nature of Grizzly Bears
Any human-caused mortality that disproportionately targets adult brown bears will likely have evolutionary consequences that manifest in the surprisingly short span of decades rather than millennia or even centuries. Such has been the case in Sweden within a remarkable 70 (plus or minus) years after institution of sport hunting in 1943. This hunting regime followed an interlude of 50 years when bears were given some degree of protection. Before that, bears in Scandinavia—as everywhere else in the world—were subject to state-sponsored slaughter.
As context, brown bears are potentially long-lived and, when adults, relatively invulnerable to predators other than humans. Because skill at foraging and negotiating space with other bears increases with age, there is ample evidence that the maternal competence of females increases as they get older. Litter sizes get larger and survival of the resulting cubs increases.
In other words, female brown bears have evolved to (figuratively) exploit the payoffs associated with a long prospective life. Instead of committing themselves to a risky and energetically expensive glut of reproduction during their youth, they instead husband themselves so as to exploit the reproductive benefits of a long life. Male bears contribute to these benefits by exerting dominance over space and breeding opportunities until old age, which creates a comparatively stable social environment within which females can go about their business.
Hunting and other forms of human-caused mortality targeting adult brown bears distort and even overthrow evolutionary regimes that selected over many millennia for the benefits of a long life. Hunting throws the male-centric world into disarray and upheaval, thus disrupting the social realm of females. Hunting of reproductive females, even when only without cubs or yearlings, shortens their life expectancy and negates the longer-term reproductive benefits that would normally accrue for them.
Hunting of solitary reproductive females also increases the advantages of holding onto offspring for a longer period of time, slowing the pace of reproduction to a degree that prospectively offsets any gains in cub survival coming from longer maternal care. In other words, females that expel their offspring sooner more likely end up dead—and thus out of the evolutionary game—simply because solitary females are literally considered “fair game” by trophy hunters. And, yet, the payoff for females that provide their young with more extended care depends entirely on whether they survive their obligatory solo intervals, and whether, in the end, their lifetime reproductive success is reduced or not. Odds are the net result is negative.
The upshot of adult-biased human-caused mortality—for example, sport hunting—is selection for shorter-lived animals with a faster pace of reproduction and less dependence on learning and social facility for survival. The nearest analog is probably American or Asiatic black bears—which reproduce at a faster pace and tend to live shorter lives, but in forested environments that sustain and foster such traits.
In other words, we would no longer have grizzly or brown bears as we know them now. For those who don’t give a damn, this is probably no loss. For those of us now and in the future who cherish grizzly bears as they are, such willful harm would be tragic.
The Charade of Science-Based Grizzly Bear Management
Interestingly, despite having ample relevant data, the Interagency Grizzly Bear Study Team, which holds purview over bear research in the Yellowstone ecosystem, has not bothered to investigate any of the prospective effects of hunting on grizzly bears and has, instead, exclusively focused on politically expedient research that supports removal of ESA protections.
But this is not for lack of interest in the topic of hunting effects among North American researchers. Most notably, Steve Stringham and Rob Wielgus published several papers using data from this continent providing early evidence of infanticide triggered by male-biased morality. Two other North Americans, Chris Darimont and Fred Allendorf, have, among others, also done their share to elucidate the long-term, distorting, and potentially detrimental evolutionary consequences of artificial selection regimes precipitated by the emergence of humans as a major cause of mortality among mammals.
None of this empirical or theoretical work has been referenced, much less acknowledged, by grizzly bear managers in the northern Rockies despite its acute relevance to current lethal regimes and trophy-hunting plans. But, then, this shouldn’t be surprising given that the invocation of “science-based” management by such managers is often simply a charade. For more on this, see recent publications by Darimont et al. (2018) and Artelle et al. (2018), as well as numerous articles by myself documenting the subversion, neglect, and politicization of science in management of Yellowstone’s grizzly bears (e.g.; , A Poverty of Bureaucrats, Fog of Science I, Fog of Science II, 3% is Not Enough, What's In a Grizzly Name, A Recipe for Killing, The Wonderful Wizard, Partisan Scientists I, Partisan Scientists II, Yellowstone's Irreplaceable Grizzlies, Divvying Up the Dead, Let Them Eat Grizzly Cake, Politspeak of Social Carrying Capacity, Grizzly Sardine Can Blues).
Some Relevant Publications
Allendorf, F. W., England, P. R., Luikart, G., Ritchie, P. A., & Ryman, N. (2008). Genetic effects of harvest on wild animal populations. Trends in Ecology & Evolution, 23(6), 327-337.
Allendorf, F. W., & Hard, J. J. (2009). Human-induced evolution caused by unnatural selection through harvest of wild animals. Proceedings of the National Academy of Sciences, 106(Supplement 1), 9987-9994.
Artelle, K. A., Reynolds, J. D., Treves, A., Walsh, J. C., Paquet, P. C., & Darimont, C. T. (2018). Hallmarks of science missing from North American wildlife management. Science Advances, 4(3), eaao0167.
Bischof, R., Swenson, J. E., Yoccoz, N. G., Mysterud, A., & Gimenez, O. (2009). The magnitude and selectivity of natural and multiple anthropogenic mortality causes in hunted brown bears. Journal of Animal Ecology, 78(3), 656-665.
Bischof, R., Bonenfant, C., Rivrud, I. M., Zedrosser, A., Friebe, A., Coulson, T., ... & Swenson, J. E. (2018). Regulated hunting re-shapes the life history of brown bears. Nature Ecology & Evolution, 2(1), 116.
Darimont, C. T., Carlson, S. M., Kinnison, M. T., Paquet, P. C., Reimchen, T. E., & Wilmers, C. C. (2009). Human predators outpace other agents of trait change in the wild. Proceedings of the National Academy of Sciences, 106(3), 952-954.
Darimont, C. T., Fox, C. H., Bryan, H. M., & Reimchen, T. E. (2015). The unique ecology of human predators. Science, 349(6250), 858-860.
Darimont, C. T., Paquet, P. C., Treves, A., Artelle, K. A., & Chapron, G. (2018). Political populations of large carnivores. Conservation Biology.
Frank, S. C., Ordiz, A., Gosselin, J., Hertel, A., Kindberg, J., Leclerc, M., ... & Zedrosser, A. (2017). Indirect effects of bear hunting: a review from Scandinavia. Ursus, 28(2), 150-164.
Frank, S. C., Leclerc, M., Pelletier, F., Rosell, F., Swenson, J., Bischof, R., ... & Zedrosser, A. (2018). Sociodemographic factors modulate the spatial response of brown bears to vacancies created by hunting. Journal of Animal Ecology, 87(1), 247-258.
Gosselin, J., Zedrosser, A., Swenson, J. E., & Pelletier, F. (2015). The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears. Proc. R. Soc. B, 282(1798), 20141840.
Gosselin, J., Leclerc, M., Zedrosser, A., Steyaert, S. M., Swenson, J. E., & Pelletier, F. (2017). Hunting promotes sexual conflict in brown bears. Journal of Animal Ecology, 86(1), 35-42.
Leclerc, M., Frank, S. C., Zedrosser, A., Swenson, J. E., & Pelletier, F. (2017). Hunting promotes spatial reorganization and sexually selected infanticide. Scientific Reports, 7, 45222.
Loveridge, A. J., Searle, A. W., Murindagomo, F., & Macdonald, D. W. (2007). The impact of sport-hunting on the population dynamics of an African lion population in a protected area. Biological Conservation, 134(4), 548-558.
Milner, J. M., Nilsen, E. B., & Andreassen, H. P. (2007). Demographic side effects of selective hunting in ungulates and carnivores. Conservation Biology, 21(1), 36-47.
Steyaert, S. M., Kindberg, J., Swenson, J. E., & Zedrosser, A. (2013). Male reproductive strategy explains spatiotemporal segregation in brown bears. Journal of Animal Ecology, 82(4), 836-845.
Steyaert, S. M., Swenson, J. E., & Zedrosser, A. (2014). Litter loss triggers estrus in a nonsocial seasonal breeder. Ecology and Evolution, 4(3), 300-310.
Stringham, S. F. (1980). Possible impacts of hunting on the grizzly/brown bear, a threatened species. International Conference on Bear Research & Management, 4, 337-349.
Stringham, S. F. (1983). Roles of adult males in grizzly bear population biology. International Conference on Bear Research & Management, 5, 140-151.
Swenson, J. E., Sandegren, F., Söderberg, A., Bjärvall, A., Franzén, R., & Wabakken, P. (1997). Infanticide caused by hunting of male bears. Nature, 386(6624), 450.
Van de Walle, J., Pigeon, G., Zedrosser, A., Swenson, J. E., & Pelletier, F. (2018). Hunting regulation favors slow life histories in a large carnivore. Nature Communications, 9, 1100.
Wielgus, R. B., & Bunnell, F. L. (1994). Dynamics of a small, hunted brown bear Ursus arctos population in southwestern Alberta, Canada. Biological Conservation, 67(2), 161-166.
Wielgus, R. B., & Bunnell, F. L. (1995). Tests of hypotheses for sexual segregation in grizzly bears. The Journal of Wildlife Management, 59(3), 552-560.
Wielgus, R. B., & Bunnell, F. L. (2000). Possible negative effects of adult male mortality on female grizzly bear reproduction. Biological Conservation, 93(2), 145-154.
Zedrosser, A., Pelletier, F., Bischof, R., Festa-Bianchet, M., & Swenson, J. E. (2013). Determinants of lifetime reproduction in female brown bears: early body mass, longevity, and hunting regulations. Ecology, 94(1), 231-240.