Breeding migrations by bighorn sheep males are driven by mating opportunities

Lassis, Roxane; Festa-Bianchet, Marco; Pelletier, Fanie

doi:10.1002/ece3.8692

Cited by 5 publications

(10 citation statements)

References 72 publications

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a_{i}

and population of origin

o_{i}

to migrate temporally into the other population between times t and t + 1 was derived from Lassis et al (2022a) as:

p_{migration} ()(,,, a_{i}, o_{i}, t) goodbreak= ε \frac{1}{1 + italicexp ()(, goodbreak- ()(, λ_{0} goodbreak+ λ_{1} a_{i} goodbreak+ λ_{2} a_{i}^{2} goodbreak+ λ_{3} italicsr ()(,, o_{i}, t) goodbreak+ λ_{4} N_{o, m} ()(,, o_{i}, t)))}

where

ε \in (][, 0, 1)

is the flow scale between populations (values in Tables S5 and S6). Parameters

λ_{0}, λ_{1}, λ_{2}, λ_{3}, λ_{4}

are the regression coefficients of age and demographic characteristics on male breeding migration rate (literature estimates in Table S3);

italicsr

the adult sex ratio (Equation ); and

N_{o, m} \in N_{P, m}, N_{H, m}

the number of competing males in the population of origin.

italicsr ()(,, o_{i}, t) goodbreak= ({, \begin{matrix} \frac{N_{P, f} ()(, t)}{N_{P, m} ()(, t)} & italicif \end{matrix})

…”

Section: Methodsmentioning

confidence: 99%

“…Each year, males could undertake breeding migrations. The probability of breeding migration depended upon mating opportunities within the population of origin, determined by male age and local availability of reproductive females (Hogg & Forbes, 1997; Lassis et al, 2022a). Therefore, the probability of male i of age

a_{i}

and population of origin

o_{i}

to migrate temporally into the other population between times t and t + 1 was derived from Lassis et al (2022a) as:

p_{migration} ()(,,, a_{i}, o_{i}, t) goodbreak= ε \frac{1}{1 + italicexp ()(, goodbreak- ()(, λ_{0} goodbreak+ λ_{1} a_{i} goodbreak+ λ_{2} a_{i}^{2} goodbreak+ λ_{3} italicsr ()(,, o_{i}, t) goodbreak+ λ_{4} N_{o, m} ()(,, o_{i}, t)))}

where

ε \in (][, 0, 1)

is the flow scale between populations (values in Tables S5 and S6).…”

Section: Methodsmentioning

confidence: 99%

“…The probability of breeding migration depended upon mating opportunities within the population of origin, determined by male age and local availability of reproductive females (Hogg & Forbes, 1997;Lassis et al, 2022a). Therefore, the probability of male i of age a i and population of origin o i to migrate temporally into the other population between times t and t + 1 was derived from Lassis et al (2022a) as:…”

Section: Breeding Migrationmentioning

confidence: 99%

“…For instance, Russ et al, 2004 found that a no‐take reserve in the Philippines increased density and harvest of surgeonfish ( Acanthuridae spp) and jacks ( Carangidae spp) in nearby exploited areas. In terrestrial systems, a few studies investigated the potential of protected areas to limit the effects of trophy hunting on horn length of ungulates including impala, Aepyceros melampus , greater kudu, Tragelaphus strepsiceros , sable antelope, (Crosmary et al, 2013 ), and bighorn sheep (Lassis et al, 2022a ; Poisson et al, 2020 ). These studies found limited evidence that protected areas provided a rescue to adjacent harvested areas.…”

Section: Introductionmentioning

confidence: 99%

“…Greater decreases in horn growth rate were documented in jurisdictions with higher harvest pressure on large‐horned males (LaSharr et al, 2019 ; Morrissey et al, 2021 ), supporting the crucial role of harvest rate on the probability that selective harvest would lead to evolutionary changes (Festa‐Bianchet, 2017 ). Although permanent dispersal in this species is rare (Festa‐Bianchet, 1986 ), many males undertake breeding migrations to seek mating opportunities outside their natal population (Hogg, 2000 ; Lassis et al, 2022a ). Breeding migrants from protected areas could provide genetic contributions to harvested populations (Tallmon et al, 2004 ; Whiteley et al, 2015 ).…”

Section: Introductionmentioning

confidence: 99%

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Genetic rescue from protected areas is modulated by migration, hunting rate, and timing of harvest

Lassis

Festa-Bianchet

Walle

et al. 2023

Evolutionary Applications

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In terrestrial and marine ecosystems, migrants from protected areas may buffer the risk of harvest‐induced evolutionary changes in exploited populations that face strong selective harvest pressures. Understanding the mechanisms favoring genetic rescue through migration could help ensure evolutionarily sustainable harvest outside protected areas and conserve genetic diversity inside those areas. We developed a stochastic individual‐based metapopulation model to evaluate the potential for migration from protected areas to mitigate the evolutionary consequences of selective harvest. We parameterized the model with detailed data from individual monitoring of two populations of bighorn sheep subjected to trophy hunting. We tracked horn length through time in a large protected and a trophy‐hunted populations connected through male breeding migrations. We quantified and compared declines in horn length and rescue potential under various combinations of migration rate, hunting rate in hunted areas and temporal overlap in timing of harvest and migrations, which affects the migrants' survival and chances to breed within exploited areas. Our simulations suggest that the effects of size‐selective harvest on male horn length in hunted populations can be dampened or avoided if harvest pressure is low, migration rate is substantial, and migrants leaving protected areas have a low risk of being shot. Intense size‐selective harvest impacts the phenotypic and genetic diversity in horn length, and population structure through changes in proportions of large‐horned males, sex ratio and age structure. When hunting pressure is high and overlaps with male migrations, effects of selective removal also emerge in the protected population, so that instead of a genetic rescue of hunted populations, our model predicts undesirable effects inside protected areas. Our results stress the importance of a landscape approach to management, to promote genetic rescue from protected areas and limit ecological and evolutionary impacts of harvest on both harvested and protected populations.

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a_{i}

and population of origin

o_{i}

to migrate temporally into the other population between times t and t + 1 was derived from Lassis et al (2022a) as:

p_{migration} ()(,,, a_{i}, o_{i}, t) goodbreak= ε \frac{1}{1 + italicexp ()(, goodbreak- ()(, λ_{0} goodbreak+ λ_{1} a_{i} goodbreak+ λ_{2} a_{i}^{2} goodbreak+ λ_{3} italicsr ()(,, o_{i}, t) goodbreak+ λ_{4} N_{o, m} ()(,, o_{i}, t)))}

where

ε \in (][, 0, 1)

is the flow scale between populations (values in Tables S5 and S6). Parameters

λ_{0}, λ_{1}, λ_{2}, λ_{3}, λ_{4}

are the regression coefficients of age and demographic characteristics on male breeding migration rate (literature estimates in Table S3);

italicsr

the adult sex ratio (Equation ); and

N_{o, m} \in N_{P, m}, N_{H, m}

the number of competing males in the population of origin.

italicsr ()(,, o_{i}, t) goodbreak= ({, \begin{matrix} \frac{N_{P, f} ()(, t)}{N_{P, m} ()(, t)} & italicif \end{matrix})

…”

Section: Methodsmentioning

confidence: 99%

a_{i}

and population of origin

o_{i}

to migrate temporally into the other population between times t and t + 1 was derived from Lassis et al (2022a) as:

p_{migration} ()(,,, a_{i}, o_{i}, t) goodbreak= ε \frac{1}{1 + italicexp ()(, goodbreak- ()(, λ_{0} goodbreak+ λ_{1} a_{i} goodbreak+ λ_{2} a_{i}^{2} goodbreak+ λ_{3} italicsr ()(,, o_{i}, t) goodbreak+ λ_{4} N_{o, m} ()(,, o_{i}, t)))}

where

ε \in (][, 0, 1)

is the flow scale between populations (values in Tables S5 and S6).…”

Section: Methodsmentioning

confidence: 99%

Section: Breeding Migrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Genetic rescue from protected areas is modulated by migration, hunting rate, and timing of harvest

Lassis

Festa-Bianchet

Walle

et al. 2023

Evolutionary Applications

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Bighorn Sheep and Mountain Goats

Whiting,

Bleich,

Bowyer

et al. 2023

Rangeland Wildlife Ecology and Conservation

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Bighorn sheep (Ovis canadensis), and to a lesser extent mountain goats (Oreamanos americanus), historically occupied much of the mountainous rangelands of western North America. Both ungulates inhabit rugged terrain and feed on grasses, forbs, and browse. Bighorn sheep and mountain goats are widely recognized for their consumptive and non-consumptive value. Indigenous peoples valued these species for cultural and subsistence purposes. Populations of these ungulates have declined since the latter part of the nineteenth century—for mountain goats, this decline has occurred particularly in the southern portion of their distribution. Historical declines have been attributed to unregulated harvest, habitat loss, competition with non-native ungulates, and disease contracted from domestic livestock. Regulated hunting has played an important role in the conservation of bighorn sheep, and recent reintroductions of these ungulates have bolstered current populations in rangelands of western North America. Although competition for habitat is minimal for bighorn sheep and mountain goats with domestic livestock (compared with other wild ruminants or feral equids), diseases of domestic sheep and domestic or exotic goats have long posed challenges to the conservation of bighorn sheep. In parts of their distributions, mountain goats and bighorn sheep are sympatric, and both species may encounter domestic livestock on grazing allotments on public or private rangelands. If management of bighorn sheep and mountain goats is the goal, spatial and temporal separation is recommended between these species and domestic sheep and goats; doing so will improve the conservation of populations of bighorn sheep and mountain goats and their habitat on rangelands of western North America.

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