Research Interests

Population Ecology of Small Mammals

Survival and Abundance of Meadow Jumping Mice

For the past six years, I have been studying the abundance and survival of meadow jumping mice (Zapus hudsonius) in central Colorado. Meadow jumping mice are widely distributed from southern Alaska to northern Georgia and northern New Mexico. One of the smallest mammalian hibernators, meadow jumping mice hibernate from approximately late September to early May. Preparation for and the physiological stress of hibernation may cause decreased survival rates in meadow jumping mice, but there is little empirical evidence for such seasonal survival changes.

Survival of Small Mammals in Northern Sandhill Prairie and Greasewood Scrub Managed Habitats of Central Colorado

The Ord's kangaroo rat (Dipodomys ordii), northern grasshopper mouse (Onychomys leucogaster) and deer mouse (Peromyscus maniculatus) are the most common rodents found in greasewood and sandsage dominated uplands of Pueblo Chemical Depot (PCD). PCD is an Army munitions depot located 15 miles east of Pueblo, Colorado, which is dominated by greasewood scrub, northern sandhill prairie, and shortgrass prairie habitats. Three years of mark-recapture studies of rodent populations at PCD have allowed habitat-specific and season-specific estimates of survival rate. Little is known about seasonal survival rates for xeric shrub rodents, and with the use of grasshopper abundance estimates and vegetation cover and composition estimates, these models can determine survival rate changes associated with changes in food abundance.

Conservation Biology

Preble's Meadow Jumping Mouse at the U.S. Air Force Academy

With the changes in the availibility and spatial arrangement of wildlife habitat, some species and subspecies are experiencing declines in abundance and survival. One such subspecies in Colorado is the Preble's meadow jumping mouse (Z. h. preblei), which is found along riparian corridors from Colorado Springs, Colorado, north to the southeastern Wyoming (Preble's distribution map). This subspecies, named after Edward A. Preble who revised the genus in 1899, was listed as threatened in 1998. Some of the healthiest populations of Preble's mouse are found along the riparian communities of the U.S. Air Force Academy, near Colorado Springs. Mark-recapture studies have allowed seasonal estimates of survival rate and abundance. Vegetation monitoring in the same habitats will allow a better understanding of how riparian cover changes and vegetation composition changes impact survival rates for this rare small mammal.

Bat Population Monitoring

Despite the conservation attention some bat species have received there are few reliable estimates of abundance or survival. Most of these estimates are based on roost counts, anecdotal captures or exit counts that lack accurate assessments of process and sampling variance. Estimating bat population dynamics is inherently difficult, but the need for improving these methods is imperative for effective conservation of bat populations. Without reliable population parameter estimates, wildlife managers and land managers will have difficulty measuring the success of conservation strategies or appropriately directing conservation resources. Most bat conservation strategies focus on the preservation of cave and mine roost sites, and minimizing human disturbance at these locations. Baseline estimates of survival, abundance and emigration/immigration rates at particular mines or mine systems are invaluable tools for assessing the true impact human disturbance may have on cavernicolous bats.

I have developed a pilot monitoring protocol that can be used on certain cave- and mine-dwelling bat populations. The techniques and mark-recapture equipment have yet to be tested.

 

Habitat Use and Conservation of Longnose Leopard Lizard

The longnose leopard lizard is one of the largest lizards found in the major desert systems of North America. It inhabits xeric shrublands from eastern Oregon to western Colorado and from southern Idaho to northern Mexico. Studies of longnose leopard lizard movement and microhabitat use have found lizards utilize several ha of sparsely-covered shrubs with minimal grass cover. However, there is limited information on longnose leopard lizard movement and habitat use in western Colorado, where populations may be declining. To study longnose leopard lizard habitat use and movement in the eastern part of its range, we radio-collared seven lizards on Cannonball Mesa in Canyons of the Ancients National Monument, Montezuma County, Colorado. We found longnose leopard lizards’ mean home range size was 20 ha, and lizards utilized habitats with medium cover of one-seeded juniper and Mormon tea, but with little grass cover. Because longnose leopard lizards occupy relatively large parcels of xeric shrublands with minimal grass cover, populations may be more and more isolated as shrublands are cleared and invaded by exotic grasses. It is possible that longnose leopard lizards act as indicators of healthy, undisturbed shrublands in the arid Southwest.

 

Physiological Ecology

Small Mammal Hibernators and the Importance of Unsaturated Fatty Acids for Overwinter Survival

Mammalian hibernators are able to withstand prolonged periods of hypothermia with body temperatures approaching or dropping below freezing. Such marked physiological stresses necessitate behavioral and physiological modifications. Key to surviving these periods of reduced body temperatures and energetic limitations is acquiring adequate fat stores. Both the quantity and quality of fat deposits play a role in hibernation success.

Increase essential fatty acid (EFA) content lengthens hibernation bout, lowers body temperature, and decreases periodicity of arousal. Thus, some EFAs are selectively sought and retained by hibernators. To date, little is known about the types of EFAs that are acquired by small (<30 g) mammalian hibernators. Golden-mantled ground squirrels (Spermophilus lateralis, approximately 150 g) selectively acquire and retain two EFAs, linoleic acid and alpha-linolenic acid. When subjected to polyunsaturated diets, the yellow pine chipmunk (Eutamias amoenus, approximately 60 g), undergoes longer hibernation bouts, maintains lower body temperatures, and has lower metabolic rates than chipmunks subjected to saturated fatty acid diets.

Although, EFAs are important to mammalian hibernators, few studies have attempted to identify the sources of EFA in the environment. Since most animals are unable to manufacture EFAs they must incorporate EFAs via their diet. Yellow-bellied marmots (Marmota flaviventris) increased consumption of cow parsnip (Heracleum lanatum), which possessed high concentrations of the EFA linoleic acid, prior to hibernation.

I am collecting serum from one of the smallest mammalian hibernators, Zapus hudsonius (meadow jumping mouse), to determine what EFAs this species retains prior to and after emerging from hibernation. Also, I will identify what the likely sources of dietary EFA are by collecting likely food items from the surrounding area. Associating physiological requirements with dietary preferences would allow more informed management of habitat needs for this species and other hibernators, and will begin to clarify the food web dynamics within the habitats where jumping mice are found.

 

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