Effects of distribution, behavior, and climate on mule deer survival

Abstract

Mule deer (Odocoileus hemionus hemionus) populations in North America are a valuable economic wildlife resource, with the managed harvest of this species reflecting societal values and recreational opportunities in many parts of the western United States. Managing mule deer populations while allowing for harvest requires an understanding of the species’ population dynamics, including the specific factors associated with population change. We conducted a 7‐year (2005–2012) study designed to investigate habitat use and survival of mule deer in eastern Oregon, USA. We used known‐fate data for 408 adult female radio‐collared mule deer to estimate monthly survival rates and to investigate factors that might affect these rates, including seasonal distribution, temporal effects (seasonal, annual, and trends across season and year), movement behavior, and local weather and regional climatic covariates. Variation in survival rates of female mule deer was best explained by an additive effect of migration behavior, differences in survival during the fall migration period compared to the rest of the annual cycle, and precipitation levels on winter ranges of individual deer. Estimates of annual survival were higher for migrants (0.81–0.82), compared to residents (0.76–0.77). Survival was lower for migrants and residents during fall migration (Oct–Nov) and higher amounts of winter precipitation increased survival of both groups. The results of our study suggest that migrating to potentially higher quality summer foraging areas outweighed the cost of traveling through unfamiliar habitats and energy expenditure associated with migration. © 2018 The Wildlife Society.

Prevalence and Mechanisms of Partial Migration in Ungulates

“…(Sawyer et al, 2016) + (Nicholson et al, 1997) ? (Sawyer et al, 2016;Schuyler et al, 2019) + (Nicholson et al, 1997)…”

“…The Terminal Investment Hypothesis states that older (past their prime) individuals are more likely to devote more resources toward ensuring successful reproduction than younger (yearling or prime-aged) individuals because they anticipate fewer future reproductive events (Clutton-Brock et al, 1982;Clutton-Brock, 1984;Bercovitch et al, 2009). When applied to migration, this hypothesis predicts that ungulates might have a propensity to remain resident while young so as to prioritize their own survival by avoiding risks that can occur during migration (e.g., from predation or anthropogenic factors; Nicholson et al, 1997;Hebblewhite and Merrill, 2011;Schuyler et al, 2019); as they age, they might accept greater risks to migrate to increase access to resources for investment in their terminal offspring (Fryxell and Sinclair, 1988a;Albon and Langvatn, 1992). The age at which this hypothesis might occur in ungulates could be quite old; indeed, Eggeman et al (2016) showed potential evidence that elk became more likely to migrate with age in Alberta, Canada, but migrants rarely switched to a resident tactic after aging (>15 years old).…”

Habitat Use Informs Species Needs and Management: A Reply to Maestas et al.

“…In New Mexico, USA, nutritional limitations and drought on summer and early autumn range caused female mule deer to enter winter with low body fat and was the best predictor of survival (Bender et al 2007). In south-central Oregon, mule deer that migrated to higher elevation summer range (i.e., forested communities) had higher survival rates than those mule deer that were resident on winter range (i.e., juniper woodlands and sagebrush cover types) yearround (Schuyler et al 2019). Mule deer typically migrate from low elevation winter ranges to higher elevation summer ranges for increased foraging opportunity (D'Eon and Serrouya 2005, Monteith et al 2011).…”

All routes are not created equal: An ungulate's choice of migration route can influence its survival

“…Past studies have linked the survival of large herbivores to weather patterns, vegetation, predation risk (Bender, Lomas, & Browning, ; DeCesare et al, ) and other factors known to directly affect or index nutritional condition (Bishop, White, Freddy, Watkins, & Stephenson, ; Monteith et al, , ). Furthermore, some studies have suggested migratory ungulates have lower rates of survival than their resident counterparts (Nicholson, Bowyer, & Kie, ; Schuyler, Dugger, & Jackson, ), and within the migratory segment, those that migrate further may encounter more anthropogenic risks (Sawyer, Middleton, Hayes, Kauffman, & Monteith, ). Expanding this growing body of work to understand how mortality risk might be influenced by various migratory parameters could further solidify the connection between migration and demography, and importantly, refine our ability to detect, and potentially mitigate, previously unknown risk factors that regulate large herbivores populations.…”