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Special section: Controversies in mountain sheep management

2017; Wiley; Volume: 82; Issue: 1 Linguagem: Inglês

10.1002/jwmg.21400

1937-2817

Mark S. Boyce, Paul R. Krausman,

Rangeland and Wildlife Management

The Journal of Wildlife ManagementVolume 82, Issue 1 p. 5-7 Editor's MessageFree Access Special section: Controversies in mountain sheep management Mark S. Boyce, Mark S. Boyce University of AlbertaSearch for more papers by this authorPaul R. Krausman, Paul R. Krausman University of AlbertaSearch for more papers by this author Mark S. Boyce, Mark S. Boyce University of AlbertaSearch for more papers by this authorPaul R. Krausman, Paul R. Krausman University of AlbertaSearch for more papers by this author First published: 15 November 2017 https://doi.org/10.1002/jwmg.21400Citations: 10AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat The conservation and management of bighorn sheep (Ovis canadensis) represents some of the most challenging issues in contemporary wildlife management including disease, hunting, livestock-wildlife conflicts, and sustainable harvest. Over 100 years ago bighorn sheep were extirpated over vast regions of the lower 48 United States by overharvest, conflicts with agriculture, and mortality caused by livestock-borne diseases (Buechner 1960). Extensive translocations and protection led to the recovery of bighorn populations in many areas to the extent that hunting is now allowed in most western states and provinces of the United States and Canada. However, serious management issues remain because wild sheep are highly vulnerable to parasites and disease that can be transmitted from domestic livestock. Further management controversy exists because throughout their distribution mountain sheep (both bighorn and Dall's sheep [O. dalli]) are managed primarily as a trophy game animal, which is under increasing criticism (Di Minin et al. 2016). The Wildlife Society (TWS) has a position statement on hunting that endorses the use of hunting in wildlife management when supported by science and socio-economic considerations (TWS 1996). We believe that sustainable hunting should be in the future of mountain sheep management in North America, but current practices for predator and harvest management warrant renewed evaluation. Our intent with this Special Section is to encourage an evaluation of management for mountain sheep conservation. We begin this special section with a review by Bleich et al. (2018) of a case study of the translocation of bighorns to North Dakota, USA. For many years translocations have been a prevalent method for recovering bighorn populations with animals sourced from multiple locations, as in the North Dakota project. Generally, the source of animals for translocation influences success (Frair et al. 2007, Mills 2017) and in the North Dakota case the source of origin influenced recruitment. If habitats are sufficient to support a viable population of bighorns, many translocations have resulted in persistent populations. Translocations have heightened the concerns about cougar (Puma concolor) predation, which can be a substantial threat to the success of translocations of desert bighorns (O. canadensis nelsoni). Bighorn translocations and management have been enhanced by targeted removal of cougars that can become specialist predators in New Mexico, USA and elsewhere, reviewed here by Rominger (2018). Whether control of cougar populations needs to be pervasive in bighorn management remains open to question, but it might ensure persistence of small, threatened populations such as the subspecies of bighorns (O. c. sierrae) in the Sierra Nevada, California, USA (Johnson et al. 2013) and the translocated herd of desert bighorn sheep in Pusch Ridge Wilderness, Arizona, USA (Krausman 2017). Transporting diseases is another burden associated with translocation of mountain sheep (Boyce et al. 2011). Because one of the most serious diseases of mountain sheep is pneumonia, we invited a comprehensive review by Cassirer et al. (2018). Seldom can wild sheep persist when there is contact with domestic sheep or goats because diseases are latent in domesticated animals. Managing to minimize disease transmission from domesticated animals to wild sheep impinges on the fundamental right of private landowners in North America to determine how they manage livestock on their own land. Avoiding grazing management conflicts on public lands might be easier to accomplish but still requires careful coordination between agricultural and wildlife interests (Carpenter et al. 2014). Trophy hunting is justified in many places across the globe because of economic returns that can benefit conservation (Di Minin et al. 2016, International Union of the Conservation of Nature [IUCN] 2016). This also is true for mountain sheep in North America where in several jurisdictions hunting licences are auctioned to generate considerable revenues for conservation programs (Hurley et al. 2015). Yet, selective hunting of large males has the potential to reduce horn size with negative consequences (Festa-Bianchet 2017). Invited papers by Coulson et al. (2018) and Heffelfinger (2018) address the question of whether selective harvest by trophy hunters might be causing evolutionary change, thereby degrading the quality of mountain sheep. The first paper to claim an evolutionary response to hunter selection (Coltman et al. 2003) used a quantitative genetic animal model but failed to eliminate the possible influence of change in environment as an alternative explanation for phenotypic change (Postma 2006, Hadfield et al. 2010). Coltman (2008) acknowledged the limitations identified by Postma (2006), yet the original Coltman et al. (2003) paper continues to be cited heavily as definitive evidence of the evolutionary effect of trophy hunting (Darimont et al. 2009, Pelletier et al. 2012; >350 papers from 2007–2017 in Web of Science). Coulson et al. (2018) examine how horn size is likely to respond to trophy hunting in a quantitative genetics model, concluding that selection must be intensive over several generations to produce a measurable evolutionary response. Heffelfinger (2018) reports that the intensity of selection by trophy hunters is seldom high and that responses to selection by hunters are usually confounded by nutrition and other variables. The issue is not whether selective hunting can have an evolutionary consequence (i.e., causing genetic change; Coulson et al. 2018) but the magnitude of change and whether it is likely to be detected with limited data (Hendry 2017). The animal model from quantitative genetics estimates evolution with a negative bias (van Benthem et al. 2017) and is unlikely to yield definitive results with a small assemblage of pedigrees, calling to question the small effect detected by Pigeon et al. (2016) estimated to be only 9% of phenotypic variance in horn length (Douhard et al. 2017). Additionally, gene flow from parks and protected areas readily can swamp the selective effects of hunting (Tenhumberg et al. 2004). Pelletier et al. (2014) dismissed this effect by addressing phenotypic rescue instead of the potential influence of dispersal on genetics in hunted populations, but phenotypic rescue is quite a different question than gene flow swamping an evolutionary response. For example, demography is affected by hunting because harvesting old males results in younger males breeding (Traill et al. 2014), but this change in phenotypes need not reflect any evolutionary response. A small amount of dispersal would be sufficient to counteract the effect of selection (Lenormand 2002); thus, a few animals moving from parks into hunted areas and surviving to breed would be more than adequate to swamp any selective effect. Such dispersers need not be large males but rather simply carriers of genes from protected areas that have not been under selection. Finally, we invited Monteith et al. (2018) to examine whether the practice of restricting harvests to mature male mountain sheep is sound herd management. Previous studies have reported that harvests of females can keep population size low enough to sustain good range condition (Jorgenson et al. 1993a, b, 1998; Wishart 2006), whereas harvesting only a small number of mature males cannot achieve herd size objectives. The resistance to harvesting females is reminiscent of the strong push back to harvesting white-tailed deer (Odocoileus virginianus) females in Wisconsin during the 1940s (Leopold 1992); convincing mountain sheep hunters to kill females likewise will require hunter education. Mountain sheep are the only mammals in North America managed almost exclusively as a trophy game animal. Given the resistance to trophy hunting (Di Minin et al. 2016, IUCN 2016), we might do better to focus on sustainable harvest optimization (Boyce et al. 1999). Based on an analysis of horn size of trophy bighorns in the Boone and Crockett records, horn size of bighorns appears to be increasing rather than decreasing (Monteith et al. 2013), indicating that trophy hunting is not causing a deterioration in males. However, horn size of trophy thin-horned sheep (e.g., Dall's sheep) appears to be decreasing, an effect that could be due to selection or shifts to younger age males under harvest pressure (Monteith et al. 2013). Hunting trophy registries do not constitute an unbiased measure of horn size in mountain sheep (Pelletier et al. 2012); thus, interpretation of these data should be approached cautiously. Also, we caution that the approaches to detect trends in such time-series data are a statistical challenge requiring special attention because observations through time are not independent (Woodward 2014). When data are adequate, trends among various jurisdictions could be used for replication (Link and Sauer 1997). Management and conservation of mountain sheep in North America highlight some of the most contentious issues in wildlife management today including conflicts with managing for livestock, contending with views on trophy hunting, and moving toward sustainable harvest management. The papers selected for this special section cannot resolve these issues, but they will engage the conversation as we seek science-based decisions. —Mark S. Boyce Professor, University of Alberta —Paul R. Krausman Editor-in-Chief LITERATURE CITED Bleich, V. C., G. Sargeant, and B. P. Wiedmann. 2018. Ecotypic variation in population dynamics of reintroduced bighorn sheep: implications for management. Journal of Wildlife Management 82:in press. Boyce, M. S., A. R. E. Sinclair, and G. C. White. 1999. Seasonal compensation of predation and harvesting. Oikos 87: 419– 426. Boyce, W. M., M. E. Weisenberger, M. C. Penedo, and C. K. Johnson. 2011. Wildlife translocation: the conservation implications of pathogen exposure and genetic heterozygosity. BMC Ecology 11: 5. Buechner, H. K. 1960. The bighorn sheep in the United States, its past, present and future. Wildlife Monographs 4: 1– 174. Carpenter, T. E., V. L. Coggins, C. McCarthy, C. S. O'Brien, J. M. O'Brien, and T. J. Schommer. 2014. A spatial risk assessment of bighorn sheep extirpation by grazing domestic sheep on public lands. Preventive Veterinary Medicine 114: 3– 10. Cassirer, E. F., K. R. Manlove, E. S. Almberg, P. L. Kamath, M. Cox, P. Wolff, A. Roug, J. Shannon, R. Robinson, R. B. Harris, B. J. Gonzales, R. K. Plowright, P. J. Hudson, P. C. Cross, A. Dobson, and T. E. Besser. 2018. Pneumonia in bighorn sheep: risk and resilience. Journal of Wildlife Management 82:in press. Coltman, D. 2008. Molecular ecological approaches to studying the evolutionary impact of selective harvesting in wildlife. Molecular Ecology 17: 221– 235. Coltman, D. W., P. O'Donoghue, J. T. Jorgenson, J. T. Hogg, C. Strobeck, and M. Festa-Bianchet. 2003. Undesirable evolutionary consequences of trophy hunting. Nature 426: 655– 658. Coulson, T., S. Schindler, L. Traill, and B. Kendall. 2018. Predicting the evolutionary consequences of trophy hunting on a quantitative trait. Journal of Wildlife Management 82:in press. Darimont, C. T., S. 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The misuse of BLUP in ecology and evolution. American Naturalist 175: 116– 125. Heffelfinger, J. 2018. Inefficiency of evolutionarily relevant selection in ungulate trophy hunting. Journal of Wildlife Management 82:in press. Hendry, A. P. 2017. Eco-evolutionary dynamics. Princeton University Press, Princeton, New Jersey, USA. Hurley, K., C. Brewer, and G. N. Thornton. 2015. The role of hunters in conservation, restoration, and management of North American wild sheep. International Journal of Environmental Studies 72: 784– 796. International Union of the Conservation of Nature [IUCN]. 2016. Informing decisions on trophy hunting. International Union for the Conservation of Nature, Gland, Switzerland. Johnson, H. E., M. Hebblewhite, T. R. Stephenson, D. W. German, B. M. Pierce, and V. C. Bleich. 2013. Evaluating apparent competition in limiting the recovery of an endangered ungulate. Oecologia 171: 295– 307. Jorgenson, J. T., M. Festa-Bianchet, M. Lucherini, and W. D. Wishart. 1993a. Effects of body size, population density, and maternal characteristics on age at first reproduction in bighorn ewes. Canadian Journal of Zoology 71: 2509– 2517. Jorgenson, J. T., M. Festa-Bianchet, and W. D. Wishart. 1993b. Harvesting bighorn ewes: consequences for population size and trophy ram production. Journal of Wildlife Management 57: 429– 435. Jorgenson, J. T., M. Festa-Bianchet, and W. D. Wishart. 1998. Effects of population density on horn development in bighorn rams. Journal of Wildlife Management 62: 1011– 1020. Krausman, P. R. 2017. And then there were none: the demise of desert bighorn sheep in the Pusch Ridge Wildlerness. University of New Mexico Press, Albuquerque, USA. Lenormand, T. 2002. Gene flow and the limits to natural selection. Trends in Ecology and Evolution 17: 183– 189. Leopold, A. 1992. The River of the Mother of God. University of Wisconsin Press, Madison, USA. Link, W. A., and J. R. Sauer. 1997. Estimation of population trajectories from count data. Biometrics 53: 488– 497. Mills, L. S. 2017. Some matchmaking advice when translocated immigrants are a population's last hope. Animal Conservation 20: 12– 13. Monteith, K. L., R. A. Long, V. C. Bleich, J. R. Heffelfinger, P. R. Krausman, and R. T. Bowyer. 2013. Effects of harvest, culture, and climate on trends in size of horn-like structures in trophy ungulates. Wildlife Monographs 183: 1– 28. Monteith, K., R. Long, T. Stephenson, V. C. Bleich, R. T. Bowyer, and T. LaSharr. 2018. Horn size and nutrition in mountain sheep: can ewe handle the truth? Journal of Wildlife Management 82:in press. Pelletier, F., M. Festa-Bianchet, and J. T. Jorgenson. 2012. Data from selective harvests underestimate temporal trends in quantitative traits. Biology Letters 8: 878– 881. Pelletier, F., M. Festa-Bianchet, J. T. Jorgenson, C. Feder, and A. Hubbs. 2014. Can phenotypic rescue from harvest refuges buffer wild sheep from selective hunting? Ecology and Evolution 4: 3375– 3382. Pigeon, G., M. Festa-Bianchet, D. W. Coltman, and F. Pelletier. 2016. Intense selective hunting leads to artificial evolution in horn size. Evolutionary Applications 9: 521– 530. Postma, E. 2006. Implications of the difference between true and predicted breeding values for the study of natural selection and micro-evolution. Journal of Evolutionary Biology 19: 309– 320. Rominger, E. M. 2018. The Gordian knot of mountain lion predation and bighorn sheep. Journal of Wildlife Management 82:in press. Tenhumberg, B., A. J. Tyre, A. R. Pople, and H. Possingham. 2004. Do harvest refuges buffer kangaroos against evolutionary responses to selective harvesting? Ecology 85: 2003– 2017. Traill, L. W., S. Schindler, and T. Coulson. 2014. Demography, not inheritance, drives phenotypic change in hunted bighorn sheep. Proceedings of the National Academy of Sciences USA 111: 13223– 13228. The Wildlife Society [TWS]. 1996. Standing position on hunting. The Wildlife Society, Bethesda, Maryland, USA. van Benthem, K. J., M. Bruijning, T. Bonnet, E. Jongejans, E. Postma, and A. Ozgul. 2017. Disentangling evolutionary, plastic and demographic processes underlying trait dynamics: a review of four frameworks. Methods in Ecology and Evolution 8: 75– 85. Wishart, W. D. 2006. Bighorns and little horns revisited. Proceedings of the Northern Wild Sheep and Goat Council 15: 28– 32. Woodward, W. A. 2014. Trend detecting. Wiley StatsRef: Statistics reference online. https://doi.org/10.1002/9781118445112.stat07818 Citing Literature Volume82, Issue1Special Section: Mountain Sheep ManagementJanuary 2018Pages 5-7 ReferencesRelatedInformation