Environmental and evolutionary effects on horn growth of male bighorn sheep

Douhard, Mathieu; Pigeon, Gabriel; Festa‐Bianchet, Marco; Coltman, David W.; Guillemette, Simon; Pelletier, Fanie

doi:10.1111/oik.03799

Cited by 42 publications

(59 citation statements)

References 88 publications

(120 reference statements)

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“…Effects of weather, however, appear mostly short term. Spring temperature during the first year of life accounted for ,1% of the variation in horn length of 3-year-old rams [47]. The long-term effects of spring temperature at birth on the probability of weaning a lamb were not significant after correction for multiple testing, suggesting that they are either non-existing or weak.…”

Section: Discussionmentioning

confidence: 93%

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Long-term fitness consequences of early environment in a long-lived ungulate

Pigeon¹,

Festa‐Bianchet²,

Pelletier³

2017

Proc. R. Soc. B.

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Cohort effects can be a major source of heterogeneity and play an important role in population dynamics. Silver-spoon effects, when environmental quality at birth improves future performance regardless of the adult environment, can induce strong lagged responses on population growth. Alternatively, the external predictive adaptive response (PAR) hypothesis predicts that organisms will adjust their developmental trajectory and physiology during early life in anticipation of expected adult conditions but has rarely been assessed in wild species. We used over 40 years of detailed individual monitoring of bighorn ewes (Ovis canadensis) to quantify longterm cohort effects on survival and reproduction. We then tested both the silver-spoon and the PAR hypotheses. Cohort effects involved a strong interaction between birth and current environments: reproduction and survival were lowest for ewes that were born and lived at high population densities. This interaction, however, does not support the PAR hypothesis because individuals with matching high-density birth and adult environments had reduced fitness. Instead, individuals born at high density had overall lower lifetime fitness suggesting a silver-spoon effect. Early-life conditions can induce long-term changes in fitness components, and their effects on cohort fitness vary according to adult environment.

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Section: Discussionmentioning

confidence: 93%

“…Spring and winter temperature and spring precipitation affect lamb survival [46]. Spring temperature also affects annual horn growth of rams [47]. Effects of weather, however, appear mostly short term.…”

Section: Discussionmentioning

confidence: 99%

Long-term fitness consequences of early environment in a long-lived ungulate

Pigeon¹,

Festa‐Bianchet²,

Pelletier³

2017

Proc. R. Soc. B.

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“…Monthly temperature and precipitations were grouped as winter (December-March), spring (April and May), summer (June-September), and autumn (October and November; Douhard et al 2017). Monthly temperature and precipitations were grouped as winter (December-March), spring (April and May), summer (June-September), and autumn (October and November; Douhard et al 2017).…”

Section: Weather and Population Densitymentioning

confidence: 99%

“…Climate change is predicted to be particularly pronounced in highly seasonal environments such as the Artic or temperate mountains (Root and Hughes 2005). Based on previous studies (Portier et al 1998, Douhard et al 2017, we expected temperature in the spring months of April and May to be the most important weather variable influencing annual variation in relative winter mass loss and summer mass gain. Summer mass gain (the difference in mass between mid-September and early June, Fig.…”

Section: Introductionmentioning

confidence: 99%

Drivers and demographic consequences of seasonal mass changes in an alpine ungulate

Douhard

Guillemette

Festa-Bianchet

et al. 2018

Ecology

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We know little about the determinants and demographic consequences of the marked seasonal mass changes exhibited by many northern and alpine mammals. We analysed 43 years of data on individual winter mass loss (the difference between mass in early June and mass in mid-September the previous year) and summer mass gain (the difference between mass in mid-September and in early June of the same year) in adult bighorn sheep (Ovis canadensis). We calculated relative seasonal mass change as a proportion of individual body mass at the start of each season. We first examined the effects of weather and population density on relative changes in body mass. We then assessed the consequences of relative seasonal mass changes on reproduction. Mean April-May temperature was the main driver of relative seasonal mass changes: warm springs reduced both relative winter mass loss and summer mass gain of both sexes, likely partially due to a trade-off between growth rate of plants and duration of access to high-quality forage. Because these effects cancelled each other, spring temperature did not influence mass in mid-September. Mothers that lost relatively more mass during the winter had lambs that gained less mass during summer, likely because these females allocated fewer resources to lactation. Winter survival of lambs increased with their summer mass gain. In males, relative mass loss during winter, which includes the rut, did not influence the probability of siring at least one lamb, possibly indicating that greater mating effort did not necessarily translate into greater reproductive success. Our findings improve our understanding of how weather influences recruitment and underline the importance of cryptic mechanisms behind the effects of climate change on demographic traits.

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“…Horns and antlers are not critical for survival, especially when compared with body growth or maintenance of body stores. Thus, young males prioritize physical development over growth in horn‐like structures (Festa‐Bianchet et al , Michel et al , Douhard et al ), a situation analogous to that of females in which maintenance takes precedence over allocation of resources to reproduction or growth of young (Monteith et al , Martin and Festa‐Bianchet ). As a result, nutritional status of populations plays a critical role in growth of those costly structures.…”

Section: The Trifecta: Age Genetics and Nutritionmentioning

confidence: 99%

Horn size and nutrition in mountain sheep: Can ewe handle the truth?

et al. 2017

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Horns, antlers, and other horn-like structures are products of sexual selection, confer reproductive advantages, and are heritable and honest indicators of individual quality. In addition to serving key biological functions, horns and antlers garner societal interest that, when combined with the powerful motivation to acquire trophy animals, likely has spawned a growing hornographic culture fixated on males with exceptional horn-like structures. The concern that harvest of large, fast-growing males may cause evolutionary change to the very trait being sought has been the source of controversy in the popular and scientific literature over the past 2 decades. Mountain sheep (i.e., bighorn and thinhorn; Ovis spp.), possibly the only large ungulates in North America managed almost exclusively as trophy species throughout their ranges, embody this controversy, which has led to polarizing views among scientists and stakeholders as to how mountain sheep should be managed. Our goal in this commentary was to discuss the relative contributions of the key ecological and intrinsic factors that influence horn growth, how those factors might interact with harvest strategies, and identify what determinants of horn size are most amenable to management and most effective in achieving desired outcomes. Despite repeated results demonstrating that age or nutrition frequently override genetic contributions to size of horns, attention has been given to the role of genetics and its relationship to harvest of mountain sheep. Given the hyperbole surrounding trophy management and big horns, we suggest the importance of females in the management of mountain sheep has been largely forgotten. Maternal condition can instigate life-long effects on size and growth of males (via maternal effects), and abundance of females, in turn, affects nutritional limitation within populations through density-dependent feedbacks. If production of males with large horns is an objective, we contend that management programs should, integrate monitoring of nutritional status of populations, and where evidence indicates nutritional limitation through density dependence, seek to regulate abundance and per capita nutrition via harvest of females. We propose that extrinsic regulation (i.e., removal by harvest or translocation) is the most effective way to manage per capita availability of forage resources and, thus, nutritional limitation on growth of males. Not only can female harvest improve growth in body size and horns of males through enhanced nutrition of growing males and their mothers, such management also 1) may yield a nutritional buffer against environmental stochasticity and erratic population fluctuations, 2) be employed in areas where other management alternatives such as habitat manipulation may not be feasible, 3) may reduce frequency or magnitude of epizootic die-offs, and 4) will increase hunter opportunity and involvement in management. Ultimately, we call for greater recognition of the pervasive role of the ewe, and other female ungulat...

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Environmental and evolutionary effects on horn growth of male bighorn sheep

Cited by 42 publications

References 88 publications

Long-term fitness consequences of early environment in a long-lived ungulate

Long-term fitness consequences of early environment in a long-lived ungulate

Drivers and demographic consequences of seasonal mass changes in an alpine ungulate

Horn size and nutrition in mountain sheep: Can ewe handle the truth?

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