Education

To educate a man in mind and not in morals is to educate a menace to society. -Theodore Roosevelt

B&C Fellow - Sonja Smith

 

MULTI-SCALE DRIVERS OF WINTER RESOURCE SELECTION AND SEXUAL SEGREGATION IN ROCKY MOUNTAIN MULE DEER

To determine how mule deer densities and scale influence the degree and timing of sexual segregation on the East Front winter range, determine how sexes differ in physiological adaptations and foraging behavior with relation to climate and weather conditions, and test 2 hypotheses pertaining to sexual segregation in a winter range context which concern sex-differences in resource allocation and predation.

Sexual segregation (i.e., differential space and habitat use between sexes) occurs in many ruminants and is especially pronounced in northern-temperate cervids. While extensively studied and there are numerous existing hypotheses attempting to explain sexual segregation, none has been accepted universally and causes of this phenomenon are still heavily debated. Meanwhile, managing for wildlife and multiple land-use in a sustainable manner is growing in importance as demands for lands increase and diversify. Rocky Mountain mule deer (Odocoileus hemionus hemionus) inhabit the eastern front of the Rocky Mountains (i.e., East Front) in north-central Montana, and during winter, congregate in low elevation at densities up to 100/km2. There is limited information available on the ecological characteristics of mule deer on the East Front, and an understanding of how mule deer mitigate for the harsh climatic conditions characteristic of this area is important to distinguish habitat features that make up winter ranges. 

One of the greatest threats to the East Front, and many areas of the West in particular, is subdivision. For instance, mule deer densities can be extremely high on winter ranges in Montana, and depletion of important winter range to development can affect deer distribution in other seasons as mule deer widely distribute themselves and exhibit fidelity to specific sites. Livestock grazing also affects mule deer, via changing the abundance of forage and cover as well as altering mule deer abundance, foraging behavior and habitat use. Because each sex may respond to subdivision, livestock, habitat, and population management differently, understanding the consequences and mechanisms for these differences are important for the sustainable management of mule deer. Because they occupy a wide-range of habitats throughout western North America and exhibit considerable sexual body-size dimorphism (i.e., males approximately 33% larger than females), mule deer make an ideal subject for examining sexual segregation.

To determine potential causes of sexual segregation in northern-temperate cervids, it is necessary to remove hypotheses from a solely theoretical framework and field-test them across a broad range of species, areas, seasons, and scales. We will examine reasons for sexual segregation in a mule deer population that winters on the East Front. Our research will address 3 specific questions: 1) how do deer densities and scale (size of sampling unit) influence the degree and timing of sexual segregation on winter range, 2) how do the sexes differ physiologically and behaviorally to mitigate for climate conditions on the East Front, and 3) do resources or predation explain multi-scale habitat selection and sexual segregation in Rocky Mountain mule deer? 

We will deploy VHF collars on 15 (8 female, 7 male) mule deer on the Boone and Crockett Club's Theodore Roosevelt Memorial Ranch during winter 2009/10. We will locate radiocollared deer to collect data on sex-specific habitat selection and foraging behavior. We will also collect fecal samples to analyze for fecal glucocorticoid metabolites and fecal nitrogen, indices used to gauge physiological stress and nutrition. A number of animals will also be harvested to collect information on sex-specific ruminal adaptations and changes in body condition throughout the winter. This study will define optimal mule deer use of winter ranges, providing information for land use planning to minimize impacts to important habitat structure (e.g., through subdivisions) or quality (e.g., through grazing). We will also provide management agencies with the degree of segregation and habitat use differences to guide survey planning to efficiently and comprehensively census the mule deer population.


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Sonja Smith
University of Montana

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"The wildlife and its habitat cannot speak. So we must and we will."

-Theodore Roosevelt