Migratory Disturbance Thresholds with Mule Deer and Energy Development

Sawyer, Hall; Lambert, Mallory Sandoval; Merkle, Jerod A.

doi:10.1002/jwmg.21847

Cited by 28 publications

(34 citation statements)

References 63 publications

(90 reference statements)

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“…Our results in combination with those of other studies on mule deer (Sawyer et al 2017, 2020) support maintaining cover habitat and refuge areas free from development so that deer can adapt their behavior without being displaced wholesale from their ranges. Landscape planning to ensure the minimization of the industrial footprint (e.g., roads, pipeline, processing stations) is critical for the maintenance of such cover habitat.…”

Section: Management Implicationssupporting

confidence: 87%

“…In our heavily developed study area, around 4% of the landscape is disturbed by well pads, facilities, and roads. Deer still use these areas, albeit in an altered manner, but we documented no large‐scale avoidance as in the study by Sawyer et al (2020).…”

Section: Discussionsupporting

confidence: 63%

“…Landscape planning to ensure the minimization of the industrial footprint (e.g., roads, pipeline, processing stations) is critical for the maintenance of such cover habitat. More dispersed development, provided it does not lead to a significantly larger road network, might be more effective at minimizing impacts to deer and is supported by the surface disturbance thresholds documented by Sawyer et al (2020). Although focusing mitigation on the drilling phase of development seems intuitive, our results offer some optimism that natural gas impacts might be more short‐lived than previously thought and provides for feasible options for mule deer conservation in development planning considerations.…”

Section: Management Implicationsmentioning

confidence: 78%

“…It might be tempting to interpret the lack of demographic response to the production phase as evidence for removing drilling restrictions and speeding the transition to production, but this could be misguided. If the density differences recorded in this study were a function of an initial response by deer to drilling, removing restrictions could elicit local population declines through largerscale avoidance as seen in mule deer and pronghorn in Wyoming (Sawyer et al 2019(Sawyer et al , 2020. Thus, we propose that planning be based on conditions present on proposed development areas until further research focused on scenarios with more active drilling over longer periods of time can be conducted.…”

Section: Management Implicationsmentioning

confidence: 95%

“…Although our study did not include naïve deer, comparisons to our results suggest deer can persist at higher densities in proximity to development in our study area with more vegetative and topographic cover. Likewise, life-history stage is important when considering thresholds; Sawyer et al (2020), working with mule deer during migration, found deer use during migration strongly declined at surface disturbance levels of around 3%. However, they did not assess any demographic consequences of these responses.…”

Section: Covariatementioning

confidence: 99%

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Behavioral and Demographic Responses of Mule Deer to Energy Development on Winter Range

Northrup

Anderson

Gerber

et al. 2021

Wildlife Monographs

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Anthropogenic habitat modification is a major driver of global biodiversity loss. In North America, one of the primary sources of habitat modification over the last 2 decades has been exploration for and production of oil and natural gas (hydrocarbon development), which has led to demographic and behavioral impacts to numerous wildlife species. Developing effective measures to mitigate these impacts has become a critical task for wildlife managers and conservation practitioners. However, this task has been hindered by the difficulties involved in identifying and isolating factors driving population responses. Current research on responses of wildlife to development predominantly quantifies behavior, but it is not always clear how these responses scale to demography and population dynamics. Concomitant assessments of behavior and population‐level processes are needed to gain the mechanistic understanding required to develop effective mitigation approaches. We simultaneously assessed the demographic and behavioral responses of a mule deer population to natural gas development on winter range in the Piceance Basin of Colorado, USA, from 2008 to 2015. Notably, this was the period when development declined from high levels of active drilling to only production phase activity (i.e., no drilling). We focused our data collection on 2 contiguous mule deer winter range study areas that experienced starkly different levels of hydrocarbon development within the Piceance Basin.We assessed mule deer behavioral responses to a range of development features with varying levels of associated human activity by examining habitat selection patterns of nearly 400 individual adult female mule deer. Concurrently, we assessed the demographic and physiological effects of natural gas development by comparing annual adult female and overwinter fawn (6‐month‐old animals) survival, December fawn mass, adult female late and early winter body fat, age, pregnancy rates, fetal counts, and lactation rates in December between the 2 study areas. Strong differences in habitat selection between the 2 study areas were apparent. Deer in the less‐developed study area avoided development during the day and night, and selected habitat presumed to be used for foraging. Deer in the heavily developed study area selected habitat presumed to be used for thermal and security cover to a greater degree. Deer faced with higher densities of development avoided areas with more well pads during the day and responded neutrally or selected for these areas at night. Deer in both study areas showed a strong reduction in use of areas around well pads that were being drilled, which is the phase of energy development associated with the greatest amount of human presence, vehicle traffic, noise, and artificial light. Despite divergent habitat selection patterns, we found no effects of development on individual condition or reproduction and found no differences in any of the physiological or vital rate parameters measured at the population level. However, deer density and annual increases in density were higher in the low‐development area. Thus, the recorded behavioral alterations did not appear to be associated with demographic or physiological costs measured at the individual level, possibly because populations are below winter range carrying capacity. Differences in population density between the 2 areas may be a result of a population decline prior to our study (when development was initiated) or area‐specific differences in habitat quality, juvenile dispersal, or neonatal or juvenile survival; however, we lack the required data to contrast evidence for these mechanisms.Given our results, it appears that deer can adjust to relatively high densities of well pads in the production phase (the period with markedly lower human activity on the landscape), provided there is sufficient vegetative and topographic cover afforded to them and populations are below carrying capacity. The strong reaction to wells in the drilling phase of development suggests mitigation efforts should focus on this activity and stage of development. Many of the wells in this area were directionally drilled from multiple‐well pads, leading to a reduced footprint of disturbance, but were still related to strong behavioral responses. Our results also indicate the likely value of mitigation efforts focusing on reducing human activity (i.e., vehicle traffic, light, and noise). In combination, these findings indicate that attention should be paid to the spatial configuration of the final development footprint to ensure adequate cover. In our study system, minimizing the road network through landscape‐level development planning would be valuable (i.e., exploring a maximum road density criteria). Lastly, our study highlights the importance of concomitant assessments of behavior and demography to provide a comprehensive understanding of how wildlife respond to habitat modification. © 2021 The Wildlife Society.

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Section: Management Implicationssupporting

confidence: 87%

Section: Discussionsupporting

confidence: 63%

Section: Management Implicationsmentioning

confidence: 78%

Section: Management Implicationsmentioning

confidence: 95%

Section: Covariatementioning

confidence: 99%

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Behavioral and Demographic Responses of Mule Deer to Energy Development on Winter Range

Northrup

Anderson

Gerber

et al. 2021

Wildlife Monographs

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Responses to natural gas development differ by season for two migratory ungulates

Lambert

Sawyer

Merkle

2022

Ecological Applications

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While migrating, animals make directionally persistent movements and may only respond to human-induced rapid environmental change (HIREC), such as climate and land-use change, once a threshold of HIREC is surpassed. In contrast, animals on other seasonal ranges (e.g., winter range) make more localized and tortuous movements while foraging and may have the flexibility to adjust the location of their range and the intensity of use within it to minimize interactions with HIREC. Because of these seasonal differences in movement, animals on seasonal ranges should avoid areas that contain any level of HIREC, however, during migration, animals should use areas that contain low levels of HIREC, avoiding it only once a threshold of HIREC has been surpassed. We tested this hypothesis using a decade of GPS collar data collected from migratory mule deer (Odocoileus hemionus; n = 56 migration, 143 winter) and pronghorn (Antilocapra americana; n = 70 migration, 89 winter) that winter on and migrate through a natural gas field in western Wyoming. Using surface disturbance caused by well pads and roads as an index of HIREC, we evaluated behavioral responses across three spatial scales during winter and migration seasons. During migration, both species tolerated low levels of disturbance. Once a disturbance threshold was surpassed, however, they avoided HIREC. For mule deer, thresholds were consistently ~3%, whereas thresholds for pronghorn ranged from 1% to 9.25% surface disturbance. In contrast to migration, both species generally avoided all levels of HIREC while on winter range. Our study suggests that animal responses to HIREC are mediated by season-specific movement patterns. Our results provide further evidence of ungulates avoiding human disturbance on winter range and reveal disturbance thresholds that trigger mule deer and pronghorn responses during migration: information that managers can use to maintain the ecological function of migration routes and winter ranges.

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Wind‐energy development alters pronghorn migration at multiple scales

Milligan

Johnston

Beck

et al. 2023

Ecology and Evolution

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Migration is a critical behavioral strategy necessary for population persistence and ecosystem functioning, but migration routes have been increasingly disrupted by anthropogenic activities, including energy development. Wind energy is the world's fastest growing source of electricity and represents an important alternative to hydrocarbon extraction, but its effects on migratory species beyond birds and bats are not well understood. We evaluated the effects of wind‐energy development on pronghorn migration, including behavior and habitat selection, to assess potential effects on connectivity and other functional benefits including stopovers. We monitored GPS‐collared female pronghorn from 2010 to 2012 and 2018 to 2020 in south‐central Wyoming, USA, an area with multiple wind‐energy facilities in various stages of development and operation. Across all time periods, we collected 286 migration sequences from 117 individuals, including 121 spring migrations, 123 fall migrations, and 42 facultative winter migrations. While individuals continued to migrate through wind‐energy facilities, pronghorn made important behavioral adjustments relative to turbines during migration. These included avoiding turbines when selecting stopover sites in spring and winter, selecting areas farther from turbines at a small scale in spring and winter, moving more quickly near turbines in spring (although pronghorn moved more slowly near turbines in the fall), and reducing fidelity to migration routes relative to wind turbines under construction in both spring and fall. For example, an increase in distance to turbine from 0 to 1 km translated to a 33% and 300% increase in the relative probability of selection for stopover sites in spring and winter, respectively. The behavioral adjustments pronghorn made relative to wind turbines could reduce the functional benefits of their migration, such as foraging success or the availability of specific routes, over the long term.

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Migratory Disturbance Thresholds with Mule Deer and Energy Development

Cited by 28 publications

References 63 publications

Behavioral and Demographic Responses of Mule Deer to Energy Development on Winter Range

Behavioral and Demographic Responses of Mule Deer to Energy Development on Winter Range

Responses to natural gas development differ by season for two migratory ungulates

Wind‐energy development alters pronghorn migration at multiple scales

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