Effects of helicopter net‐gunning on survival of bighorn sheep

Wagler, Brittany L.; Smiley, Rachel A.; Courtemanch, Alyson B.; Anderson, Gregory J.; Lutz, Daryl; McWhirter, Doug; Brimeyer, Doug; Hnilicka, Patrick; Massing, Cody P.; German, David W.; Stephenson, Thomas R.; Monteith, Kevin L.

doi:10.1002/jwmg.22181

Cited by 10 publications

(29 citation statements)

References 44 publications

(65 reference statements)

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“…Beginning in December 2015, we captured adult females using helicopter net‐gunning (Whiskey Mountain and Jackson populations; Krausman et al, 1985; Wagler et al, 2022) or ground‐darting and chemical immobilization (Upper Shoshone population) and fitted each with an individually identifiable GPS collar (various models, Advanced Telemetry Systems, Isanti, MN, USA; Vectronics Aerospace, Berlin, Germany). Every animal collared was assigned a unique identifier (animal ID).…”

Section: Methodsmentioning

confidence: 99%

Heterogeneity in risk‐sensitive allocation of somatic reserves in a long‐lived mammal

et al. 2022

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Food quality and availability, when combined with energetic demands in seasonal environments, shape resource acquisition and allocation by animals and hold consequences for life‐history strategies. In long‐lived species with extensive maternal care, regulation of somatic reserves of energy and protein can occur in a risk‐sensitive manner, wherein resources are preferentially allocated to support survival at the cost of investment in reproduction. We investigated how Rocky Mountain bighorn sheep (Ovis canadensis), an alpine mammal in a highly seasonal environment, allocates somatic reserves across seasons. In accordance with the hypothesis of risk‐sensitive resource allocation, we expected accretion and catabolism of somatic reserves to be regulated relative to preseason nutritional state, reproductive state, and variation among populations in accordance with local environmental conditions. To test that hypothesis, we monitored seasonal changes in percent ingesta‐free body fat (IFBFat) and ingesta‐free, fat‐free body mass (IFFFBMass) in three populations of bighorn sheep in northwest Wyoming between 2015 and 2019 through repeated captures of female sheep in December and March of each year in a longitudinal study design. Regulation of somatic reserves was risk‐sensitive and varied relative to the amount of somatic reserves an animal had at the beginning of the season. Regulation of fat reserves was sensitive to reproductive state and differed by population, particularly over the summer. In one population with low rates of recruitment of young, sheep that recruited offspring lost fat over the summer in contrast to the other two populations where sheep that recruited gained fat. And yet, all populations exhibited similar changes in fat catabolism and risk sensitivity over winter. The magnitude of body fat and mass change across seasons may be indicative of sufficiency of seasonal ranges to meet energetic demands of survival and reproduction. Risk‐sensitive allocation of resources was pervasive, suggesting nutritional underpinnings are foundational to behavior, vital rates, and, ultimately, population dynamics. For species living in alpine environments, risk‐sensitive resource allocation may be essential to balance investment in reproduction with ensuring survival.

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Section: Methodsmentioning

confidence: 99%

Heterogeneity in risk‐sensitive allocation of somatic reserves in a long‐lived mammal

et al. 2022

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“…For many species of large mammals, a pre‐determined yet arbitrary window of time (e.g., 10 days, 2 weeks) often is used to censor data following capture and handling to reduce bias in survival data associated with capture events (Beringer et al 1996, Monteith et al 2014). Recent empirical evaluation has indicated that indirect effects of capture on survival may range anywhere from 3 days to 3 weeks (Ortega et al 2020, Van de Kerk et al 2020, Wagler et al 2022). We did not detect differences in daily survival of mule deer preceding and following capture.…”

Section: Discussionmentioning

confidence: 99%

“…Given that we could not confidently detect differences in daily survival before and after capture and handling (Figure 1; Table 1), we used previous literature to define a window in which to evaluate the potential indirect effects of capture (i.e., 3 days). Nevertheless, we could not assess the effect of handling protocols on a 3‐day window (Ortega et al 2020, Wagler et al 2022) because sample size of mortalities during that window was low ( n = 6). Despite having >2,000 capture events, we did not have the statistical power to evaluate possible effects of capture and handling during a post‐capture window, which strongly illustrates the likelihood that our capture protocols do not have deleterious effects on survival post capture.…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, restrictions in data collection protocols such as reducing handling times, limiting time of year when capture occurs, minimizing invasive procedures (e.g., tooth extraction for aging or rectal biopsies for disease testing), and reducing number of recaptures are often implemented to reduce presumed negative effects of handling on survival and to reduce the probability of exertional myopathy on animals. Moreover, because of the potentially unknown latent effects of capture myopathy, many wildlife practitioners censor all mortality data for a predetermined window of time following a capture and handling event, but such censorship can result in culling of meaningful data and may be unwarranted in many situations (Norton et al 2016, Wagler et al 2022). Censoring periods have ranged between 0 and 26 days (Beringer et al 1996; DelGuidice et al 2005, Hebblewhite et al 2018) for large herbivores and between 1 and 21 days for avian species (Blomberg et al 2018), with the majority of studies implementing censorship periods that are largely arbitrary (Norton et al 2016, Blomberg et al 2018).…”

mentioning

confidence: 99%

“…Censoring periods have ranged between 0 and 26 days (Beringer et al 1996; DelGuidice et al 2005, Hebblewhite et al 2018) for large herbivores and between 1 and 21 days for avian species (Blomberg et al 2018), with the majority of studies implementing censorship periods that are largely arbitrary (Norton et al 2016, Blomberg et al 2018). Despite the need for identifying the timeframe within which to appropriately censor survival data, the time at which capture and handling appears to have a measurable effect on survival is unknown for most species; however, it has been evaluated in some systems (Van de Kerk et al 2020, Wagler et al 2022).…”

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Evaluating risks associated with capture and handling of mule deer for individual‐based, long‐term research

et al. 2022

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Capture and handling techniques for individual-based, longterm research that tracks the life history of animals by recapturing the same individuals for several years has vastly improved study inferences and our understanding of animal ecology. Yet there are corresponding risks to study animals associated with physical trauma or capture myopathy that can occur during or following capture events. Rarely has empirical evidence existed to guide decisions associated with understanding the magnitude of capture-related risks, how to reduce these risks when possible, and implications for mortality censoring and survival estimates. We used data collected from 2,399 capture events of mule deer (Odocoileus hemionus) via helicopter net-gunning to compare daily survival probabilities within a 10-week period centered on a capture event and evaluated how animal age, nutritional condition (body fat), and various handling methods influenced survival before, during, and following a capture event. Direct mortality resulting from

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Disparate home range dynamics reflect nutritional inadequacies on summer range for a large herbivore

Wagler,

Smiley,

Courtemanch

et al. 2024

Ecosphere

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The spatial distribution of animals has consequences for nutrition, predator–prey dynamics, spread of diseases, and population dynamics in general. Animals must establish a home range to secure adequate resources to fuel their energy needs. Home ranges, therefore, are temporally and spatially dynamic, given the changing requirements of an animal and the availability of resources on the landscape. We used data from two populations of bighorn sheep with contrasting population dynamics following pneumonia epizootics and different habitat quality on their summer range to test the hypothesis that the distribution and size of home ranges are influenced by environmental conditions and reproductive status. We used a combination of data from 768 vegetation transects and remotely sensed metrics to index forage quality of consecutive biweekly home ranges for 27 bighorn sheep, June–August 2019–2021. There were population differences in home range dynamics that were consistent with resource limitations in the population declining in abundance. Animals in both populations increased the size of their home range through the summer in association with declining forage quality indexed by plant phenology. Furthermore, animals in the Whiskey Mountain population without offspring had home ranges more than twice the size of animals with offspring, whereas there were no differences in the home range size between animals with and without offspring in Jackson. We demonstrated that limitations young offspring impose on space use of a mother may have consequences for animals living where larger home ranges are needed to secure adequate resources—sheep on Whiskey Mountain had to travel 1000 m from escape terrain to access the same amount of biomass that the Jackson sheep could access directly adjacent to escape terrain. Forage quality and availability influence movement and space use. In the presence of disease, movement and space use may influence pathogen transmission and persistence. Thus, forage availability may play an indirect role in population dynamics in the presence of disease, which is another line of evidence for how environmental and nutritional conditions may influence population dynamics when coping with disease.

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Effects of helicopter net‐gunning on survival of bighorn sheep

Cited by 10 publications

References 44 publications

Heterogeneity in risk‐sensitive allocation of somatic reserves in a long‐lived mammal

Heterogeneity in risk‐sensitive allocation of somatic reserves in a long‐lived mammal

Evaluating risks associated with capture and handling of mule deer for individual‐based, long‐term research

Disparate home range dynamics reflect nutritional inadequacies on summer range for a large herbivore

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