Geology topics

Jill E. Randall

Publications and source records attributed to Jill E. Randall.

5 recordsLinked to original sources

USGS2026

Ungulate migrations of the Western United States, volume 6

This report, volume 6 in the “Ungulate Migrations of the Western United States” report series, showcases the migrations of 23 ungulate herds in the Western United States. The report series is produced by the Corridor Mapping Team (CMT). Led by the U.S. Geological Survey, the CMT is a collaboration among 11 State agencies, as well as regional and Federal partners, and an expanding number of Tribal wildlife agencies. The CMT was initiated in response to the U.S. Department of the Interior Secretarial Order 3362, which was signed in 2018 and provided Federal support to expand existing research efforts to study ungulate populations and conserve their migrations throughout the Western United States. Including this volume, the report series has detailed the migrations of 237 unique ungulate herds throughout the Western United States and continues to serve as a valuable resource to guide local and regional management, policy, and on-the-ground work necessary to maintain intact and functional ungulate migrations. This report highlights several guiding principles of the CMT that facilitate collaboration among the diverse set of partners and contribute to the program’s continued successes. Notably, raw global positioning system data are not shared among participating agencies and the U.S. Geological Survey, delineating migration corridors and seasonal ranges relies on empirical data, the CMT provides flexible approaches to participating State and Tribal partners, and regular CMT meetings create a framework for open communication among agency partners that supports transboundary mapping of migrations. The 237 ungulate migrations that have been included in the report series are an expanding inventory, which can help maintain ungulate migrations in perpetuity.

Arizona, California, Colorado, Idaho, Montana, Nev↗

USGS2026

Integrating climate and anthropogenic dynamics can inform multifaceted management for declining mule deer populations

Wildlife and their habitats face profound challenges from climate and landscape-scale changes that extend beyond the influence and time horizon of most biologists and land managers. In this changing environment, long-term datasets can enhance assessments of how demographic trends respond to interactions among local (e.g., habitat restoration decisions) and broad extent drivers, including energy development, to shape wildlife populations. Although many studies evaluate habitat selection or demographics for a single population, our multipopulation, multiscale study quantifies the influence of local management actions given broader environmental forces using both immediate and lagged effects. This approach may be particularly important for species with high site fidelity that may have less adaptive capacity, including mule deer ( Odocoileus hemionus ), which are experiencing widespread population declines. We analyzed a 40-year (1980–2019) dataset for 37 mule deer populations across Wyoming, USA, to test hypotheses about and quantify the relative influence of conditions within winter use areas on annual rates of juvenile recruitment. Recruitment has been strongly affected by multiple factors largely beyond the control of managers. Land cover (agriculture and shrubland) had the largest positive effects on recruitment, with estimates more than twice the magnitude of other variables, but also had limited presence in some winter use areas. The next strongest effect sizes were shared by energy developments (including oil/gas and wind energy) and climatic conditions, which, except for wind turbines, had broad distributions across winter use areas. Recruitment increased with higher mean winter temperatures and summer precipitation, but declined with wind, oil and gas developments, cumulative drought, and wildfire. Expected increases in drought and decreases in summer precipitation may constrain options to sustain mule deer populations. Although mule deer recruitment may sometimes be enhanced through habitat restoration, effects varied with treatment type, habitat type, and time since treatment. Given large constraining effects of temperature and drought, supporting drought resiliency for important habitat may be useful. Our results can be used to weigh the relative strength of threats and the value of restoration actions, interpret historic demographic change, prioritize populations for conservation, and optimize options for wildlife habitat management.

Wyoming↗

USGS2025

How sampling design of GPS collar deployment influences consistency of mapped migration corridors over time

Federal and state agencies within the United States have recently issued directives prioritizing the conservation of ungulate migration corridors and winter ranges. The ability to identify and delineate the spatial distribution of seasonal ranges underpins these policies. While such delineations are often derived from global positioning system (GPS) collar data collected for a few years on a focal population, they are being used in long-term conservation planning. Our objectives were to quantify consistency in migration corridors from year to year and cumulatively across multiple years and identify which aspects of the sampling design of GPS collar deployment will delineate a consistent and relatively complete migration corridor. We used data from 6 sub-herds of mule deer ( Odocoileus hemionus ), a species known to have high migratory fidelity, located in Wyoming and northern New Mexico, USA, monitored for 5–7 years (510 unique individuals). We calculated 2 types of migration corridors over time: cumulative corridors where each new year of data was added to all previous years and yearly corridors where each year was based only on data collected in that year. We then calculated the year-to-year consistency in the 2 types of migration corridors by calculating the percent overlap between corridors calculated in sequential years. We found that collaring a higher proportion of a sub-herd increased the consistency in migration corridors, whereas collaring new individuals via redeployments in a subsequent year of monitoring caused corridors to shift. To obtain a corridor with ≥90% consistency (i.e., approaching the complete area used by a population in our data), our results suggest that biologists should strive to collar ≥6% of a sub-herd for a minimum of 2 years. However, if ≥6% of a sub-herd cannot be collared, monitoring for longer (3–4 years) will provide roughly 90% consistency in a migration corridor estimate for mule deer. Furthermore, adding 16–25% new individuals each year will help capture variation among individuals while maintaining corridor consistency of ≥90%, leading to a more accurate delineation of the corridor. Our results provide managers with a logistical framework for collaring projects aimed at delineating migration corridors that are durable into the future.

Colorado, New Mexico, Wyoming↗

USGS2022

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

Capture and handling techniques for individual-based, long-term 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 capture efforts was 1.59%. Mean daily survival was 0.9993 ± 0.0001 (SE) during the 5-week pre-capture window, was depressed the day of capture at 0.9841 ± 0.0004, and rebounded to 0.9990 ± 0.0008 during the 5-week post-capture window. Neither capture nor handling had a detectable effect on post-capture survival, including handling time ( x̄ = 13.30 ± 1.87 min), capture time of year (i.e., Dec or Mar), tooth extraction, and the number of times an animal had been recaptured (2–17 times). Although mortality rate was slightly elevated during capture (resulting from physical trauma associated with capture), age and nutritional condition did not influence the probability of mortality during a capture event. Following a capture event, nutritional condition influenced survival; however, that relationship was consistent with expected effects of nutritional condition on winter survival and independent of capture and handling. Overall survival rates 5 weeks before capture and 5 weeks after capture were not different. A specified window of time with depressed survival following capture and handling was not evident, which contradicts the implementation of a predetermined window often used by researchers and managers for censoring mortalities that occur after capture. Previous notions that censorship of all mortality data in the 2 weeks following capture is unwarranted and risks removal of meaningful data. With previous evidence guiding our protocols for capture (e.g., reduced chase time) and handling (e.g., temperature mitigation), low direct mortality and almost undetectable indirect mortality post capture reinforces the efficacy of helicopter net-gunning for capture and recapture of mule deer in long-term, individual-based studies.

Wyoming↗

USGS2021

Short-term responses to a human-altered landscape do not affect fat dynamics of a migratory ungulate

According to risk-sensitive foraging theory, animals should make foraging decisions that balance nutritional costs and gains to promote fitness. Human disturbance is a form of perceived risk that can prompt avoidance of risky habitat over acquisition of food. Consequently, behavioural responses to perceived risk could induce nutritional costs. Population declines often coincide with increases in human disturbance, which likely is associated with direct and indirect habitat loss. Nevertheless, behavioural and physiological responses to perceived risks associated with human disturbance could be an added nutritional deficit with population-level repercussions. Using GPS-collar data from three populations of migratory mule deer Odocoileus hemionus exposed to a gradient of established industrial energy development on winter ranges where direct and indirect habitat loss were well documented, we evaluated whether exposure and behavioural responses to human disturbance alter changes in nutritional condition (i.e. fat reserves) over winter. Although animals exhibited behaviours indicative of perceived risk of human disturbance, such as increased movement rates and avoidance of infrastructure, exposure and behavioural responses to human disturbance had little to no measurable effect on fat loss over a winter. Instead, catabolism of fat reserves occurred primarily as a function of the amount of fat animals had entering winter, suggesting that, in the short term, animals were able to mitigate the energetic costs of perceived risk of human disturbance over winter. Animals, however, did not appear to overcome persistent food limitations, and animals with less food availability lost more fat over winter. Our findings heed caution in using short-term behavioural and physiological responses to inform long-term nutritional consequences of human disturbance. Although animals appear to mitigate the energetic costs of perceived risk, food limitations exacerbated by broader-scale avoidance of food near human disturbance may be the primary pathway causing the frequently observed population declines following human disturbance to pristine landscapes.

Wyoming↗