Life-history characteristics of mule deer: Effects of nutrition in a variable environment

Monteith, Kevin L.; Bleich, Vernon C.; Stephenson, Thomas R.; Pierce, Becky M.; Conner, Mary M.; Kie, John G.; Bowyer, R. Terry

doi:10.1002/wmon.1011

Cited by 226 publications

(354 citation statements)

References 310 publications

(687 reference statements)

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“…December, which we used as a metric of recruitment of young to 6 months of age (Monteith et al, 2014). We obtained recruitment data for 98 animals totalling 174 animal-years.…”

Section: Migration Fidelity Analysismentioning

confidence: 99%

Migratory plasticity is not ubiquitous among large herbivores

Sawyer

Merkle

Middleton

et al. 2018

Journal of Animal Ecology

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The migratory movements of wild animals can promote abundance and support ecosystem functioning. For large herbivores, mounting evidence suggests that migratory behaviour is an individually variable trait, where individuals can easily switch between migrant and resident tactics. The degree of migratory plasticity, including whether and where to migrate, has important implications for the ecology and conservation of large herbivores in a changing world. Mule deer (Odocoileus hemionus) are an iconic species of western North America, but are notably absent from the body of literature that suggests large herbivore migrations are highly plastic. We evaluated plasticity of migration in female mule deer using longitudinal GPS data collected from 312 individuals across nine populations in the western United States, including 882 animal‐years (801 migrants and 81 residents). We followed both resident and migratory mule deer through time to determine whether individual animals switched migratory behaviours (i.e., whether to migrate) from migratory to residency or vice versa. Additionally, we examined the fidelity of individuals to their migration routes (i.e., where to migrate) to determine whether they used the same routes year after year. We also evaluated whether age and reproductive status affected propensity to migrate or fidelity to migratory routes. Our results indicate that mule deer, unlike other large herbivores, have little or no plasticity in terms of whether or where they migrate. Resident deer remained residents, and migrant deer remained migrants, regardless of age, reproductive status or number of years monitored. Further, migratory individuals showed strong fidelity (>80%) to their migration routes year after year. Our study clearly shows that migration plasticity is not ubiquitous among large herbivores. Because of their rigid migratory behaviour, mule deer may not adapt to changing environmental conditions as readily as large herbivores with more plastic migratory behaviour (e.g., elk). The fixed migratory behaviours of mule deer make clear that conservation efforts aimed at traditional seasonal ranges and migration routes are warranted for sustaining this iconic species that continues to decline across its range.

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“…December, which we used as a metric of recruitment of young to 6 months of age (Monteith et al, 2014). We obtained recruitment data for 98 animals totalling 174 animal-years.…”

Section: Migration Fidelity Analysismentioning

confidence: 99%

Migratory plasticity is not ubiquitous among large herbivores

Sawyer

Merkle

Middleton

et al. 2018

Journal of Animal Ecology

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“…More recent methods have coupled standardized palpation scores with ultrasonographic measurements to generate live animal body fat estimates (Cook et al , ). The product of this process is an estimate of the percent ingesta‐free body fat (%IFBF) for an animal, a parameter that has become more commonly used as a metric in studies of potential management actions (Bishop et al , ; Bergman et al ), as a tool to evaluate anthropogenic influences on wildlife (Lendrum et al , Northrup et al ), and as a tool to better understand life history (Monteith et al , ; Searle et al ). Through analyzing this relatively new stream of data, we have learned that %IFBF, and presumably overall condition, among individual animals, even those taken from the same herd at that same time, is highly variable (Bergman et al ).…”

mentioning

confidence: 99%

Variation in ungulate body fat: Individual versus temporal effects

et al. 2017

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The use of ultrasonograhic measurements of muscle and body fat represent a relatively new data stream that can be used to address questions regarding ungulate condition. We have learned that measurements of body fat and presumably overall body condition among individual animals, even those taken from the same herd at that same time, are highly variable. Relatively little consideration has been given to the sources of variation in body fat and other physiological parameters in wildlife populations. We evaluated the components of variation in late‐winter mule deer (Odocoileus hemionus) body fat estimates: sampling variation (i.e., variation induced by the particular set of individuals that were sampled) and process variation (i.e., variation stemming from biological processes) with a long‐term data set (2002–2015) from Colorado, USA. We collected our data from across Colorado as part of historical research, ongoing research, and periodic population monitoring programs. Mean percent ingesta‐free body fat (%IFBF) for sampled mule deer was 7.20 ± 1.20% (SD). Covariates related to individual deer explained approximately 4% of the total variation in %IFBF and annual effects explained an additional 13% of the variation. Substantial residual variation in %IFBF (83%) remained unexplained. The source of the 83% of unexplained variation is partially linked to fine‐scale spatial dynamics but also additional individual metrics we were unable to capture, primarily the presence or absence of dependent young. We speculate that the primary factors influencing late‐winter mule deer body fat and overall condition are individual in nature. These results present a cautionary check on herd‐level inference that can be made from individual late‐winter body fat estimates and we postulate that for mule deer, alternative and additional body condition metrics may offer added utility in management scenarios. However, an important next step to better understand wildlife population health is to evaluate the sources and magnitude of variation within other body condition metrics, with the goal of further refining data that can better allow biologists to incorporate herd health into population management recommendations. © 2017 The Wildlife Society.

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“…Bobcats can be expected to cull about 30% of fawns even during the best rain years. Because they do not select unhealthy fawns, mortality is largely directly additive, but in a long‐term context, bobcat predation may be to some degree indirectly compensatory by mitigating negative density‐dependent effects on deer population vital rates in response to a fluctuating environment (Bishop et al , Forrester and Wittmer , Monteith et al ).…”

Section: Discussionmentioning

confidence: 99%

Growth and mortality of sympatric white‐tailed and mule deer fawns

et al. 2017

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Population growth rates of cervids are sensitive to changes in adult female survival, but fawn recruitment tends to be the population vital rate most susceptible to density‐dependent population‐level influences. We conducted a study of fawn survival rates and related biology in northwest Crockett County, Texas, USA, during 2004–2007 in an area where white‐tailed deer (Odocoileus virginianus) and mule deer (O. hemionus eremicus) existed sympatrically. Our fawn study was justified by the need to explain annual variation in female‐to‐fawn ratios apparent during field surveys. Using vaginal implant transmitters in radio‐marked adult females to locate birth sites, we captured, weighed, and radio‐collared fawns on 4 privately owned ranches. We monitored collared fawns daily and investigated mortalities within 24 hours of receiving a mortality signal to determine cause of death. When possible, we collected thymus glands to assess body condition. We captured 170 fawns (64 white‐tailed deer; 106 mule deer), of which 145 were of known‐age from collared females, and found that relatively heavy adult females birthed relatively heavy fawns. We also noted that mass gain of fawns and mass of fawns’ thymus glands were very low compared to other studies of fawns. We documented mortalities: 47 by predation, 47 by sickness‐starvation, 1 by conspecific trauma, and 3 undeterminable. Bobcats (Lynx rufus) were responsible for nearly all fawn predation; thymus gland and fawn mass data indicated that bobcats did not select weaker fawns. We used proportional hazards regression to assess factors influencing fawn survival and competing risks of mortality and made comparisons between the species when possible. We censored 6 fawns from our analyses and found that half of mortalities occurred within 15 days postpartum, and 12 of the 139 known‐age fawns (9%) died within 25 m of the birth site. Fawn survival was 78% at 6 days old, which was the median estimated age‐at‐capture of fawns from unknown adults. Annual fawn survival rate ranged from 50% for fawns born in 2004 to 17% for fawns born in 2006, with no overall effect of species. Fawn survival was greatest in 2004 when rain during the May–August late‐gestation and lactation period was greatest. Mule deer fawns succumbed more to sickness‐starvation than did white‐tailed deer fawns. Rates of sickness‐starvation and predation increased with deviance from mean annual birth dates and with reduced rain during the late‐gestation and lactation period. Early fawn survival increased with relative fawn mass, and sex became important at about 30 days postpartum, after which males were at greater risk of sickness‐starvation. Lunn‐McNeil competing‐risks models suggested some interaction between sickness‐starvation and predation. Fawn mortality, mass gain, thymus mass, and weaning data indicated that the populations of both deer species were chronically stressed near a carrying capacity that fluctuated annually with rain and that adult females invested little energy in rearing fawns relative to ca...

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Life-history characteristics of mule deer: Effects of nutrition in a variable environment

Cited by 226 publications

References 310 publications

Migratory plasticity is not ubiquitous among large herbivores

Migratory plasticity is not ubiquitous among large herbivores

Variation in ungulate body fat: Individual versus temporal effects

Growth and mortality of sympatric white‐tailed and mule deer fawns

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