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New Mexico State University

Faculty research

Jon Boren

Foraging Relationships Between Elk, Mule Deer and Cattle on Southwestern Forests and Rangelands.

A research study in the Lincoln National Forest was initiated in 1998 and will continue through 2000 to evaluate the foraging relationships between elk, mule deer, and cattle. The intended goals of this project will provide greatly needed knowledge about livestock, elk and mule deer interactions and will lead to an analytical tool that can be used to assist in natural resource management.

Specifically, the information derived from this study will allow inferences to be made about what habitat types these animals frequent the most at different times of the year. It also will allow estimates of forage use for each habitat type during different times of the year. Dietary overlap for these species in the different habitats also will be evaluated for the warm and cool seasons.

Lastly, the percent of forage removal attributed to each animal species will be determined for each habitat type during the warm and cool seasons. To date, study areas have been selected and field research has been initiated.

Wiebke Boeing

Colleen Caldwell

Fate, Source, and Effect of Mercury in Aquatic Systems of New Mexico.

Fish monitoring programs in New Mexico water bodies have detected total mercury concentrations in edible fish tissues that have resulted in statewide fish consumption advisories. One potential source for mercury contamination may be from atmospheric deposition which is currently being explored at a monitoring site established by the New Mexico Cooperative Fish and Wildlife Research Unit. In 1997, approximately 5,000 ng/m2 of mercury was deposited in rain events. This rate is one-half the national average for mercury in wet deposition and is relatively high considering the total rainfall in New Mexico (8 in) is less than a third of the national average.

Biomagnification of mercury has been observed in aquatic food webs in several New Mexico reservoirs. Mercury concentrations increased nearly 500 times from less than 0.01 ppm in plankton to as high as 5.0 ppm in fish-eating birds. These concentrations were near the acute toxicological effects for mercury observed in fish-eating birds and may have important long term ecological risk implications.

Martha Desmond

Grassland bird ecology, distribution and habitat selection on breeding and wintering grounds in the Chihuahuan Desert.

Grassland bird populations are declining throughout their range. Factors attributed to these declines include conversion of native grasslands to agriculture and urban uses, removal of native grazers, and encroachment of woody vegetation. Species associated with the shortgrass prairie breed throughout the Great Plains, but are concentrated on wintering grounds in the southern parts of their range, mainly in Chihuahuan Desert grasslands.

My avian research involves breeding and winter ecology of grassland adapted birds. Information on basic life history characteristics and factors that influence distribution and abundance on winter and breeding grounds is essential for understanding community dynamics and evaluating potential threats to these populations.

I am currently involved in 3 projects related to grassland birds in the southwestern United States and northern Mexico.

In Chihuahua, Mexico I am involved in a project examining the distribution, habitat preferences and life history characteristics of grassland birds on winter grounds at sites throughout the state of Chihuahua. I am particularly interested in how avian abundance and diversity among sites changes within and between winters. Eventually, I plan to use molecular markers to identify wintering grounds of genetically distinct populations of selected species and to examine movements within and between winters.

In south central New Mexico I am working with a masters student to examine the influence of seed abundance, diversity and distribution on grassland bird diversity and distribution during the nonbreeding season. We are also looking at seed selection by birds through regurgitation, and comparing it with bill morphology, and seed production and availability at the sites. This project also examines the effects of habitat type and condition on avian abundance and distribution. I also have a masters student examining burrowing owl (Athene cunicularia) reproductive success in urban areas, native grassland and desert scrub habitats.

We are interested in comparing reproductive success in native and urban areas and also among different burrow systems. We have owls nesting in burrows of rock squirrels (Spermophilus variegates), bannertailed kanagroo rats (Dipodomys spectabilis), black tailed prairie dogs (Cynomys ludovicanus), pocket gophers (Thomomys spp), natural cavities and artificial burrows. Through these studies, and others that will develop, I am interested in identifying local and landscape factors that impact grassland bird population during the breeding and nonbreeding seasons.

Martha Desmond

Genetic and morphological variation in burrowing owls throughout their New World range.

I am interested in the taxonomic status of selected species and the use of molecular markers to address conservation issues. My current research involves the taxonomic status of the burrowing owl throughout its range in North, South and Central America and the West Indies. There are 18 recognized subspecies of burrowing owls. Morphological variation among subspecies is extensive, particularly for owls from the South American continent, but does not support structuring among populations.

Mitochondrial DNA sequence data revealed a genetic split between burrowing owl populations from North and South America. This split dates back two million years to the connection of these continents via the isthmian land bridge. Subspeciation among populations within continents is of Pleistocene origin. Results from the genetic data suggest a North American origin for Burrowing Owls and subsequent dispersal via the land bridge to the South American continent. The depth of the split between burrowing owls from North and South America is consistent with species level distinction. I am pursuing this question in further detail through the use of additional data from nuclear markers and possibly ecological indicators such as behavior or vocalizations.

Gary Roemer

Apparent Competition and the Influence of Invasive Species on Community Structure and Species Endangerment.

Invasive species have been recognized as one of the main drivers of ecosystem change and native species endangerment. On the Channel Islands off the coast of California, I employed demographic methods, ecological energetics and stable isotope analysis to show how introduced feral pigs caused a wholesale restructuring of the island food web. The presence of pigs allowed golden eagles to colonize the islands and through apparent competition caused a decline in the endemic island fox. Apparent competition is a mechanism whereby two prey share a common predator, one prey is adapted to high predation pressure and the other is not. Consequently, population density of the more vulnerable prey is depressed, often to near extinction. In this case on the Channel Islands, foxes were the more vulnerable prey. Eagle predation has depressed the fox populations to such a degree that the USFWS is proposing to list the fox as endangered under the ESA and the National Park Service has implemented a recovery program to save the fox from extinction.

For more information see:

  • Roemer, G.W, C.J. Donlan, III and F. Courchamp. 2001. Golden eagles, feral pigs and insular carnivores: How exotic species turn native predators into prey. Proceedings of the National Academy of Sciences, Early Edition. In print version to be published in January 2002.
  • Roemer, G.W., T.J. Coonan, D.K. Garcelon, J. Bascompte and L. Laughrin. 2001. Feral pigs facilitate hyperpredation by golden eagles and indirectly cause the decline of the island fox. Animal Conservation 4: 307-318.

Gary Roemer

Are Social, Herbivorous Rodents Ecological Engineers: The Influence of Black-tailed Prairie Dogs on Arid Grassland Systems.

Ecosystem engineers influence community structure and function by altering resource availability to other species through physical state changes in biotic or abiotic components; their actions modify, maintain or create habitats. In a recent study, my colleagues and I propose to elucidate the potential role of prairie dogs as ecosystem engineers within a Chihuahuan Desert Grassland. We hypothesize that prairie dogs alter energy flow as well as plant species diversity and that this modification will increase foraging opportunities for bison and other grazing herbivores. We will accomplish this task by experimentally manipulating the abundance of prairie dogs, by assessing their interaction with bison, by monitoring changes in other community metrics and by tracking energy flow through the system.

Bruce Thompson

Currently Director of the New Mexico Department of Game and Fish, Santa Fe, and member of the Fishery and Wildlife Sciences Graduate Faculty.

Past research with the Department was directed at various aspects of avian ecology, GIS applications to conservation planning, sustainable management and harvest of wildlife, characteristics of resource users, and conservation communication. The research involved field and digital lab activities regarding development of landscape ecology databases, land cover mapping, animal-habitat association modeling, bird community assemblages in riparian and arid lands, wildlife association with arid lands springs, and large ungulate distribution and demography. Although much of this research was broadly directed at wildlife in a landscape setting and elucidating resource conflicts, a variety of species-specific projects have included such animals as Neotropical migrant birds, elk, bighorn sheep, chipmunks, fur-bearing mammals, and various raptors.

Raul Valdez

Mammalogy and management of big game. Authority, wild sheep of the world. Field research in U.S., Mexico, Iran, Turkmenistan, Pakistan, Kirghizstan and Mongolia.

Mammalogy and management of big game. Authority, wild sheep of the world. Field research in U.S., Mexico, Iran, Turkmenistan, Pakistan, Kirghizstan and Mongolia

Mark Andersen

Effects of Habitat Alterations by Anthropogenic Disturbances.

Habitat alterations by anthropogenic disturbances, and especially the effects of habitat fragmentation on animals, are often studied in forests. Nevertheless, patchiness and the scale of patches seem to be very important in desert ecosystems. Therefore, the effects of human modification of natural patterns of patchiness in drylands need to be addressed. The goal of this study is to examine the influence of fragmentation and patch alteration on assemblages of lizards in arid ecosystems. Lizards are important contributors to ecosystems, especially in arid zones: lizards may occur in very high densities and they are predators of arthropods, prey for larger vertebrates and burrow diggers. The study will be performed in the Negev Desert, in Israel, and in New Mexico, in the US. In the Negev, we will concentrate on a medium-scale patch alteration, utilizing a project of "savannization" which is conducted on the research site. High productivity patches are added to the natural slopes as part of the project, and we will examine the effects of this addition on the lizard species inhabiting this region. We will look at habitat selection, relative abundance, survival and reproductive success of each species. In addition, by direct observation and food abundance analysis, we will find the mechanisms that contribute to the patterns that will be detected.

We will examine what in the ecology of the lizards is affected by the habitat alteration (e.g., thermal relations, competitive relations etc.). In New Mexico, we will concentrate on large scale habitat alteration and fragmentation, caused mainly by urbanization and desertification. We will also look for interactions between human impact and natural habitat characteristics. We will measure lizard densities in areas with different levels of human impact, and different landform and vegetation, and relate differences in lizard density to differences in degree of human impact on the ecosystem.

This study will cover both community and population level processes, as well as the level of the individual lizard, leading to a better understanding of the effects of human management on an important component of an arid ecosystem.

Banner-tailed Kangaroo Rats and Shrub Invasion in Desert Grasslands.

Banner-tailed kangaroo rats (Dipodomys spectabilis) are mound-building heteromyid rodents of desert grasslands in the southwestern United States and northern Mexico. Each mound contains a complex burrow system, including caches of vegetative material, and is occupied by a single individual. Mounds differ from their surroundings in their vegetation, soil nutrient content, hydrologic properties, and soil fungi. Although both active and abandoned mounds may have shrubs (e.g., mesquite, Prosopis glandulosa; ephedra, Ephedra trifurca; creosote bush; Larrea tridentata) growing on them, active mounds tend to be kept free of vegetation by the activities of the kangaroo rat. Previous research, including our own work, has shown that kangaroo rat mounds can profoundly influence local vegetation. We propose a conceptual model of the role of banner-tailed kangaroo rat mounds in shrub invasion of desert grasslands, in which kangaroo rat mounds play a role analogous to that of tree-fall gaps in "patch-dynamics" models of forest ecosystems. Our model leads to three hypotheses concerning the role of banner-tail mounds in the dynamics of shrub invasion; the objectives of the proposed research are to test these hypotheses:

  1. Feeding preferences of D. spectabilis, in the laboratory and in the field, lead to profound effects on local vegetation, retarding the process of shrub encroachment.
  2. D. spectabilis are capable of suppressing mesquite establishment near active mounds.
  3. Mesquite seedlings establish preferentially on abandoned D. spectabilis mounds.

These objectives will be achieved through a combination of observational and experimental studies carried out in the Chihuahuan Desert grassland of the Jornada Experimental Range, Doņa Ana County, New Mexico, USA. Establishment of mesquite seedlings will be measured in proximity to active and abandoned banner-tail burrow mounds both beneath and away from mesquite plants using permanent quadrants adjacent to and away from mounds. A laboratory-based experiment to determine kangaroo rat impact on mesquite seed and seedlings using a choice arena will be carried out in an established facility on the New Mexico State University campus.

The proposed research will contribute to our knowledge of the processes involved in the conversion of desert grasslands to shrublands, thereby contributing to sustainable management of desert grassland ecosystems, which are important for livestock grazing.

Louis Bender

Biology and Management of Large Mammals

Assessing nutrition's influences on elk and mule deer populations in western North America. Declining productivity in elk and deer populations has been defined as the pre-eminent challenge facing ungulate management in the West. Decreased productivity has resulted in population declines throughout large areas of the West, limiting opportunities for sportsmen and other recreationists. The purpose of this project is to quantify the relationships between existing habitat conditions and elk/deer body condition, productivity, and population dynamics. Project goals include:

  • Identify the extent that forage conditions on elk/deer ranges influence and limit productive performance and thus potentially limit or regulate herds;
  • Explicitly identify how elk/deer habitats should be managed to best provide for nutritional well-being; and

  • Provide a strong empirical basis for developing monitoring tools and predictive models that provide for assessment of

    • the nutritional value of habitats across landscapes and
    • nutrition's influences on elk/deer herds.

Quantifying the relationships between types and amount of vegetation and herd productivity will allow the identification of management practices that result in a beneficial nutritional environment for elk/deer. Further, a second generation of habitat evaluation models will be developed to guide land management practices that best provide for the habitat-nutritional needs of elk/deer. These models can be used by state, federal and private land managers to plan and provide for these needs. Finally, this project will identify suitable techniques that provide cost-effective, validated monitoring tools that biologists can use to monitor nutritional conditions across landscapes.

Don Caccamise

Adaptations of the Chihuahuan Raven to the desert environment.

Effective management of resident populations of Canada geese (Branta canadensis) requires a reliable method to determine the migratory history of individuals during the non-breeding season. We undertook this study to determine if stable isotope analysis of feather tissue could distinguish between migratory and non-migratory populations. We obtained feather samples from northern Quebec province near Ungava Bay, Canada (30 July - 4 August 1997) and from several inland and coastal sites in northeastern United States (16 June to 3 July 1997). We analyzed for carbon, nitrogen and sulfur isotopes using a Europa mass spectrometer. We entered stable isotope ratios (delta form) into a discriminant analysis using collection site as the grouping variable (Canada, inland resident and coastal resident). We formed two significant functions that successfully discriminated among the three groups of geese. he first function accounted for most of the variance explained by the discriminant analysis, and was highly influenced by the delta-carbon values. A scatterplot of delta values revealed that coastal birds showed a higher influence of a marine diet, and birds from highly managed areas (inland resident) showed the effects of a diet from a low delta-nitrogen environment (e.g., food plants grown with artificial fertilizer). The marine pattern was similar in the Canadian samples. Our results indicate that feathers are a useful tissue source for stable isotope analysis, and that this analysis, along with further refinements, provides a reliable method for differentiating between migratory and non-migratory populations of Canada geese.

Use of stable isotope analysis to distinguish migratory and non-migratory populations of Canada Geese (Branta canadensis).

Among North American members of the genus Corvus, the Chihuahuan Raven is unique in being largely restricted to desert habitats. While this species is conspicuous and abundant, many questions remain concerning its basic biology. Among these are social aspects of breeding, seasonality of breeding, spacial patterns of habitat utilization in the breeding season and in relation to communal roosting and flocking behavior in winter. We have undertaken studies of the Chihuahuan Raven in an effort to fill in gaps concerning the basic biology of this species while attempting to better understand the the role Chihuahuan Ravens play in the broader desert community.

Dave Cowley

Innovative, pragmatic solutions to resource management problems in the American Southwest via limnology, population biology, and management planning.

My research program seeks to improve understanding of the ecological requirements of native aquatic species, the demography and genetics of their populations, aquatic community organization, and how humans modify aquatic ecosystems. The objective of my research is to discover ways that human uses of water can be adapted to foster native species management. Current research projects in my laboratory include studies on agricultural irrigation systems and how they can be used to foster conservation of native fish species, investigations on the early life history of the endangered Rio Grande silvery minnow, a geographic analysis of Rio Grande cutthroat trout populations using genetic markers (microsatellites), and study of the trophic ecology in a large warmwater reservoir.

Recent Papers:

  • Cowley, D. E., F. A. Ward, R. Deitner and M. D. Hatch. 2003. Optimizing the allocation of hatchery-produced fish among multiple stocking sites. North American Journal of Fisheries Management 23:(In press).
  • Cowley, D. E. 2003. Water requirements for endangered species - Rio Grande silvery minnow (Hybognathus amarus). Proceedings of the 47th New Mexico Water Conference:(In press).
  • Cowley, D. E., P. Shirey and C. Hohman. 2003. Agriculture irrigation systems and conservation of native fishes: Issues in the Rio Grande Valley of New Mexico. Rio Grande Basin Initiative White Paper (In press).
  • Cowley, D. E. Effective size, demographic stochasticity and environmental uncertainty in defining viable habitat size (to be submitted).

Howard Ness

US/Mexico Affairs Office.

The US/Mexico Affairs Office (MEAF) is an operating field unit located in Las Cruces, New Mexico. The office director reports to the Intermountain Region (IMR) Office Deputy Director for the Southwest Cluster of the National Park Service (NPS). The MEAF Office interacts with the subcluster of parks in collaboration with international partners, park to park partners, interagency partners, and private groups to protect and manage shared natural, historic, and cultural resources along the US/Mexico Border region. The office represents the NPS in negotiating and coordinating international programs with US/Mexico entities, facilitates research for protection of the biological diversity, particularly adjacent to the United States/Mexico Border, and coordinates educational programs for the management of natural, archeological, historic, and cultural resources. International Affairs Specialists cooperate with US/Mexico partners (government, NGOs, universities) to generate understanding and appreciation for the shared natural and cultural heritage of the United States-Mexican Border region.