Author : Mallory Sandoval Lambert
Publisher :
ISBN 13 :
Total Pages : 108 pages
Book Rating : 4.5/5 (152 download)
Book Synopsis Seasonal Responses of Mule Deer and Pronghorn to Energy Development by : Mallory Sandoval Lambert
Download or read book Seasonal Responses of Mule Deer and Pronghorn to Energy Development written by Mallory Sandoval Lambert and published by . This book was released on 2021 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt: Human-induced rapid environmental change (HIREC) underlies the Anthropocene. One principal difference between present-day and historical environmental change is the pace and scale. Just 300 years ago, 95% of Earth’s ice-free land was considered wildlands or semi-natural. Today, almost ~55% of ice-free land has been converted for human uses. This poses a challenge for animals, who must move through landscapes to eat, mate, and escape from predators. Indeed, this rapid rate of landscape change has likely not been experienced by animals in their evolutionary past. Further, animals that rely on long-term memory of past environmental conditions are struggling to track environmental change. In this thesis, I examined two key gaps in knowledge in how animals respond to HIREC. First, I assessed how the movement mechanism (oriented versus memory-based) an animal employs influences its response to HIREC (Chapter 1). Second, I assessed how responses develop over time while HIREC is occurring (Chapter 2). I used long-term datasets from 183 collared mule deer (Odocoileus hemionus) and 89 pronghorn (Antilocapra americana) that migrate through and winter on a natural gas field in western Wyoming to carry out this work. Mule deer and pronghorn rely on memory-based movements during their up to 200 km migrations and on oriented movements while on their smaller and constrained winter ranges. Mule deer use strong spatial memory during migration and have extremely high fidelity to their migration routes. Pronghorn, in contrast, are more plastic and tend to change whether and where they migrate from year to year. We evaluated responses to surface disturbance (native habitat converted to roads and well pads) using habitat use and selection analyses across three spatial scales during winter and migration periods. While using memory-based movements during migration, both species were reluctant to abandon traditional migratory routes until a disturbance threshold was surpassed, after which they avoided HIREC. For pronghorn, thresholds ranged from 1-9% surface disturbance, whereas mule deer thresholds were consistently ~3%. In contrast to the migratory responses, both species avoided HIREC across a gradient of low-high amounts of HIREC while using oriented movements on winter range. Once these overall responses were established, I then assessed whether they changed or remained constant over time (Chapter 2). Animal populations may have immediate responses to HIREC or they may develop a response over time, resulting in a time-lag between the onset of HIREC and a population’s response. With immediate responses, it is likely that individual behavioral plasticity is the underlying mechanism of a population’s response to HIREC. For time lags, it is likely that natural selection acts on personalities within a given population. Using the mule deer dataset only, I fit resource selection functions (RSF) using a Generalized Additive Mixed Model (GAMM) to evaluate temporal trends in the behavioral response to the natural gas development during both migration and while on winter range. At the population level for both migration and winter range, mule deer exhibited a time-lag response to HIREC (i.e., natural gas development). During migration, during the first 8 years of this study, mule deer avoided development only after a threshold of development was surpassed and this threshold varied from year to year. Following the 8-year lag, mule deer consistently avoided development year to year once development surpassed a ~2% threshold. For winter range, during the first 9 years, mule deer responses to development varied year to year, although they mainly avoided development. Following the 9-year lag, the avoidance of development became stronger and more consistent. At the individual level for both migration and winter range, mule deer collared for > 1 year avoided development and their response to development did not change over subsequent years, suggesting little behavioral plasticity in this population. Overall, my work demonstrates that responses to HIREC by moving animals can be non-linear, are mediated by the movement mechanism animals are primarily relying on, and may not be consistent and strong until years after the onset of landscape change. Additionally, the disturbance thresholds identified herein for mule deer and pronghorn provide land and wildlife managers in western Wyoming with specific, actionable targets that can help to maintain the ecological function of migration routes and winter ranges. Energy development is, and will continue to be, a major source of disturbance for migratory ungulates, and other sagebrush obligate species, in western North America. An estimated 800,000 km2 of land is projected to be converted for energy extraction by the year 2040. Because this and other forms of land development will continue, it is increasingly important to understand how, when, to what degree, and over what time-scale animals respond to human disturbance so that potential impacts can be minimized.
