Summer elk calf survival in a partially migratory population

Berg, Jodi; Eacker, Daniel R.; Hebblewhite, Mark; Merrill, Evelyn H.

doi:10.1002/jwmg.22330

Cited by 10 publications

(21 citation statements)

References 99 publications

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“…Collectively, this suggests wolf predation on male elk may be important only in protected areas where there are more abundant older male elk that are more vulnerable to wolves. Despite our high‐predation study area, wolves were not competing with human hunters for male elk harvest, though high predation by grizzly bears especially on neonatal elk may also limit male elk for harvest (Berg et al 2023).…”

Section: Discussionmentioning

confidence: 99%

“…B) Wildlife management unit 418 in Alberta, Canada, with roads and mortality locations of harvested male elk with known mortality locations, 2018-2020. (Hebblewhite et al 2018, Berg et al 2023. The Ya Ha Tinda elk population is partially migratory with 3 migratory tactics characterized by differences in survival and choice of summer range: eastern migrants, western migrants, and residents (Berg 2019, Martin et al 2022.…”

Section: Study Areamentioning

confidence: 99%

“…Other ungulates include, in approximate order of abundance, bighorn sheep ( Ovis canadensis ), mule deer ( Odocoileus hemionus ), white‐tailed deer ( O. virginianus ), moose ( Alces alces ), and mountain goats ( Oreamnos americanus ). Wolf predation is the leading cause of adult female elk mortality, but humans, grizzly bears, American black bears ( U. americanus ), cougars ( Puma concolor ), and coyotes ( Canis latrans ) also kill adults and neonates (Hebblewhite et al 2018, Berg et al 2023). The Ya Ha Tinda elk population is partially migratory with 3 migratory tactics characterized by differences in survival and choice of summer range: eastern migrants, western migrants, and residents (Berg 2019, Martin et al 2022).…”

Section: Study Areamentioning

confidence: 99%

“…Wolf predation is the leading cause of adult female elk mortality, but humans, grizzly bears, American black bears ( U. americanus ), cougars ( Puma concolor ), and coyotes ( Canis latrans ) also kill adults and neonates (Hebblewhite et al 2018, Berg et al 2023). The Ya Ha Tinda elk population is partially migratory with 3 migratory tactics characterized by differences in survival and choice of summer range: eastern migrants, western migrants, and residents (Berg 2019, Martin et al 2022). Male and female migrants begin migration in May or June, returning to winter ranges from September–November, whereas the residents remain year‐round on the winter range centered on the Ya Ha Tinda Ranch (Hebblewhite et al 2006, Martin 2021).…”

Section: Study Areamentioning

confidence: 99%

“…There have been fewer tests of predictions of the forage maturation hypothesis that migratory males will have larger antlers, however. The Ya Ha Tinda elk population in and adjacent to Banff National Park, Alberta, Canada (Hebblewhite et al 2006) has amongst the highest large‐carnivore mortality rates on adult female elk and neonates in North America (Brodie et al 2013, Berg et al 2023), with abundance limited by wolf and grizzly bear ( Ursus arctos horribilis ) predation (Hebblewhite et al 2018). Yet it is also one of Canada's premier trophy male elk hunting areas, with some of the largest trophy size male elk harvested in Canada.…”

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Male elk survival, vulnerability, and antler size in a transboundary and partially migratory population

et al. 2023

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Migration is a behavioral strategy used by many ungulates to access resources and avoid predation in heterogenous landscapes. If migratory individuals access higher quality forage and avoid predation, then they should attain greater fitness.Migration can also expose individuals following distinct migratory tactics to differential mortality and harvest. We investigated how transboundary migration affected male elk (Cervus canadensis) survival and antler size when subjected to harvest with different antler point restrictions (APRs) and yearround harvest by treaty First Nations in a multi-carnivore system in Alberta, Canada. We measured antler size and age for 35 unmarked, harvested male elk and 90 global positioning system (GPS)-collared adult male elk. We also estimated radiocollared elk survival and cause-specific mortality (105 elkyears) from 2018 to 2020. Antler size increased as a non-linear function of age and exposure to high quality forage for migrants. The biological effect size of exposure to higher quality forage (i.e., lower biomass) obtained by migrants was variable but biologically equivalent to the antler size difference (i.e., 33-54 cm) predicted between 5-and 6-year-old male elk. Annual mortality rate was 0.304 and the primary cause of death was hunting (cumulative incidence functions [CIF] mortality rate = 0.203, n = 33 mortalities) of which a third was by First Nations treaty harvest (CIF = 0.101, n = 12).

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Section: Discussionmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

mentioning

confidence: 99%

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Male elk survival, vulnerability, and antler size in a transboundary and partially migratory population

et al. 2023

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Variable spatiotemporal ungulate behavioral response to predation risk

Schooler,

Svoboda,

Kellner

et al. 2024

Ecosphere

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Prey must balance resource acquisition with predator avoidance for survival and reproduction. To reduce risk of predation, prey may avoid areas with high predator use, but if they are unable to due to resource acquisition requirements, they may instead change their habitat use or movement speed to mitigate predation risk. Prey risk response may depend on spatially or temporally varying forage availability as well as seasonal variation in prey vulnerability and availability of alternate foods for predators. To quantify how prey respond to spatial and temporal variation in risk of brown bear predation, we examined Roosevelt elk (Cervus canadensis roosevelti) spatiotemporal behavior responses to brown bear (Ursus arctos) habitat use on Afognak and Raspberry islands, Alaska, using Global Positioning System location data during elk parturition (20 May–15 June), summer (16 June–20 September), and autumn (21 September–10 November). During parturition and summer, elk used forest and shrub landcover in areas of higher brown bear probability of use. During parturition, elk used areas with lower forage productivity in areas of higher bear probability of use, and movement speed decreased with higher bear probability of use, especially in shrub landcover. During summer, elk used areas with higher forage productivity in areas of higher brown bear probability of use. During autumn, elk were less likely to use areas with higher bear habitat probability of use across landcover categories and forage productivity. During summer and autumn, elk movement speed increased with higher brown bear probability of use. Elk behavioral response to risk of brown bear predation could increase energy expenditure and decrease their ability to acquire forage, therefore negatively impacting survival and reproduction with spatiotemporal variation in risk response potentially amplifying these impacts.

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Large herbivores in a partially migratory population search for the ideal free home

Martin

Hebblewhite

Merrill

2022

Ecology

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Migration is a tactic used across taxa to access resources in temporally heterogenous landscapes. Populations that migrate can attain higher abundances because such movements allow access to higher quality resources, or reduction in predation risk resulting in increased fitness. However, most migratory species occur in partially migratory populations, a mix of migratory and nonmigratory individuals. It is thought that the portion of migrants in a partial migration population is maintained either through (1) a population-level evolutionary stable state where counteracting density-dependent vital rates act on migrants and residents to balance fitness or (2) conditional migration, where the propensity to migrate is influenced by the individual's state. However, in many respects, migration is also a form of habitat selection and the proportion of migrants and residents may be the result of density-dependent habitat selection. Here, we test whether the theory of Ideal Free Distribution (IFD) can explain the coexistence of different migratory tactics in a partially migratory population. IFD predicts individuals exhibit density-dependent vital rates and select different migratory tactics to maximize individual fitness resulting in equal fitness (λ) between tactics. We tested the predictions of IFD in a partially migratory elk population that declined by 70% with 19 years of demographic data and migratory tactic switching rates from >300 individuals. We found evidence of density dependence for resident pregnancy and adult female survival providing a fitness incentive to switch tactics. Despite differences in vital rates between migratory tactics, mean λ (fitness) was equal. However, as predicted by the IFD, individuals switched tactics toward those of higher fitness. Our analysis reveals that partial migration may be driven by tactic selection that follows the ideal free distribution. These findings reinforce that migration across taxa may be a polymorphic behavior in large herbivores where migratory tactic selection is determined by differential costs and benefits, mediated by density dependence.

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Summer elk calf survival in a partially migratory population

Cited by 10 publications

References 99 publications

Male elk survival, vulnerability, and antler size in a transboundary and partially migratory population

Male elk survival, vulnerability, and antler size in a transboundary and partially migratory population

Variable spatiotemporal ungulate behavioral response to predation risk

Large herbivores in a partially migratory population search for the ideal free home

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