Determining Timing of Births and Habitat Selection to Identify Lambing Period Habitat for Bighorn Sheep

Robinson, Rusty; Smith, Tom S.; Whiting, Jericho C.; Larsen, Randy T.; Shannon, Justin M.

doi:10.3389/fevo.2020.00097

Cited by 10 publications

(7 citation statements)

References 79 publications

(164 reference statements)

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“…Vertical movements may also effectuate refuge from predation. Because the migratory season of bighorn sheep generally corresponds with lambing, ewes must balance heightened nutritional requirements with selection of habitat that accommodates safe lamb rearing 59,60 , leading to shifts in habitat selection by bighorn ewes after lambing 61 . In the eastern Sierra, mountain lions hunt bighorn sheep with particular success at low elevations 62,63 .…”

Section: Discussionmentioning

confidence: 99%

Pursuit and escape drive fine-scale movement variation during migration in a temperate alpine ungulate

John,

Avgar,

Rittger

et al. 2024

Preprint

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Climate change reduces snowpack, advances snowmelt phenology, drives summer warming,alters growing season precipitation regimes, and consequently modifies vegetation phenologyin mountain systems. Altitudinal migrants cope with seasonal variation in such conditions bymoving between seasonal ranges at different elevations, but vertical movements may becomplex and are often not unidirectional during the spring migratory season. We uncoverdrivers of vertical movement variation in an endangered alpine specialist, Sierra Nevadabighorn sheep. We used integrated step-selection analysis to determine factors that promotevertical movements, and factors that drive selection of destinations after vertical movements.Our results reveal that high temperatures consistently drive uphill movements, and providesome evidence for the contribution of precipitation events to downhill movements.Furthermore, bighorn select destinations that have a high relative index of forage growth andmaximize delay since snowmelt. These results indicate that although Sierra bighorn seek outforaging opportunities related to landscape phenology, they compensate for short-termenvironmental stressors by undertaking brief vertical movements. Migrants may therefore beimpacted by future warming and increased storm frequency or intensity, both in terms of theirfine-scale vertical movements, and in terms of tradeoffs between forage access and predationrisk.

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Section: Discussionmentioning

confidence: 99%

Pursuit and escape drive fine-scale movement variation during migration in a temperate alpine ungulate

John,

Avgar,

Rittger

et al. 2024

Preprint

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show abstract

“…In other areas, researchers using remote cameras to estimate abundance of ungulates could first identify congregation sites using global positioning system (GPS) data. For example, the Utah Division of Wildlife Resources currently has over 300 GPScollared bighorn sheep in 15 herds across the state (Robinson et al, 2020). From those GPS data, investigators could identify locations at which animals congregate to deploy remote cameras to estimate abundance in those populations.…”

Section: Discussionmentioning

confidence: 99%

Using camera traps to estimate ungulate abundance: a comparison of mark–resight methods

Taylor

Bates²,

Whiting

et al. 2021

Remote Sens Ecol Conserv

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Many global wildlife populations are experiencing unprecedented declines. Estimates of population abundance are needed to effectively manage common species and to conserve vulnerable species. Camera traps have advanced as wildlife monitoring tools for ungulates and can provide improved methods of estimating population abundance. Little is known, however, about how camera traps set for ungulates compare with traditional methods (e.g., ground and aerial surveys) used simultaneously. From 2012 to 2014, we captured and radio collared 34 female and 32 male bighorn sheep (Ovis canadensis) in a closed population in Utah, USA. Each collar had a unique letter and number combination. We then estimated number of young, females and yearlings, males and population abundance using multiple methods simultaneously: helicopter surveys, resight surveys performed from the ground, camera trap surveys using marked but not individually identifiable individuals and camera trap surveys using marked and individually identifiable animals. All methods estimated similar abundance. Across years, ages and sexes, however, camera trap surveys produced the most consistent and precise estimates of abundance for adult females and yearlings, lambs and the population. That method was less intrusive and safer than helicopter surveys. Our results indicate that camera trap surveys using photographs of marked animals in which the majority of the population visits a specific resource can produce precise estimates of abundance that are safer, as well as less intrusive and expensive than traditional methods. Using camera traps also creates a permanent record of photographs that can be archived and reanalyzed to answer future ecological and population questions. Finally, this method of estimating abundance can be used in other areas with ungulates that congregate around resources (e.g., watering sites or mineral licks).

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“…We included a quadratic term for ndvi end to allow selection of intermediate levels of greenness, which may indicate actively growing, nutritious forage. High values of NDVI may also indicate dense shrub cover, which bighorn avoid (Devoe et al 2020;Lula et al 2020;Robinson et al 2020). We interacted ndvi start with movement parameters (sl, log_sl, cos_ ta), expecting that bighorn might increase movement speed and directional travel when starting in areas of low NDVI.…”

Section: Forage Model Covariatesmentioning

confidence: 99%

Movement models and simulation reveal highway impacts and mitigation opportunities for a metapopulation-distributed species

et al. 2023

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Context When human-made barriers impact wildlife by limiting habitat connectivity, simulation can reveal movements lost to fragmentation, strategies to restore corridor function, and potential benefits of corridor restoration. Objectives Guided by previous genetic research, we examined desert bighorn sheep movement near two highways that restrict gene flow and modelled their movement and habitat selection behavior. The ultimate goal was to simulate movement without highway barriers as a means to site crossing structures that mitigate fragmentation and to reveal their benefits for habitat reachability. Methods We fit integrated step selection functions (iSSFs) to GPS data from 9 bighorn populations near highways in California. After comparing iSSF simulations to validation data, we simulated 8200 bighorn-years of movement—200 year-long tracks each for 41 individuals—on a landscape with and without highways. We derived utilization distributions (UD) from simulations to identify probable high-use locations along the highways, compare these locations to previously predicted genetic corridors and roadkill events, and estimate changes in habitat reachability and elevation without these barriers. Results Simulation UDs correlated well with observed bighorn movements. Barrier-free simulations indicated preferred corridors across highway-blocked valleys, often at the same locations predicted by landscape genetics models (4 of 6 genetic-based corridors matched simulation-based corridors), and where bighorn roadkill events occurred (3 of 3 roadkill events occurred at simulation-predicted corridors). Relative to barrier-present simulations, barrier removal increased accessible habitat for 8 of 9 populations, with increases ranging from 7 to 138% per population. Barrier-free conditions allowed movement to higher elevations in two populations. Conclusion Animal movement simulation can effectively assess fragmentation impacts and reveal mitigation options when other data sources are scarce. Our simulations confirm previously predicted corridors, provide detailed locations for targeted mitigation, and suggest certain corridors pose greater habitat-related benefits.

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Determining Timing of Births and Habitat Selection to Identify Lambing Period Habitat for Bighorn Sheep

Cited by 10 publications

References 79 publications

Pursuit and escape drive fine-scale movement variation during migration in a temperate alpine ungulate

Pursuit and escape drive fine-scale movement variation during migration in a temperate alpine ungulate

Using camera traps to estimate ungulate abundance: a comparison of mark–resight methods

Movement models and simulation reveal highway impacts and mitigation opportunities for a metapopulation-distributed species

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