John R. Morgart

Influence of topography and GPS fix interval on GPS collar performance

Abstract Topography, vegetation, and animal behavior may influence the performance of Global Positioning System (GPS) telemetry collars, affecting fix success rates and location error. We reviewed the scientific literature published from 1995 to June 2004 to determine the fix intervals used and fix success rates obtained in studies using GPS telemetry. We also programmed GPS telemetry collars with 6 different fix intervals and placed them at fixed locations of varying topography in the Cabeza Prieta National Wildlife Refuge, Arizona from August 2003–May 2004. Fix interval affected fix success rates both in our field study (99, 98, 96, 94, 93, 92% fix success rate for 0.25, 0.5, 1, 4, 6, and 13-hour fix intervals, respectively) and in our analysis of data obtained from scientific literature (r2=0.531, P≤0.001), with shorter fix intervals being associated with higher fix success rates. Topography affected the fix success rate (F2, 77=12.017, P≤0.001), location error (F2, 77=6.76, P=0.002), and proportion of 3-dimensional (3-D) fixes (F2,77=10.184, P≤0.001), resulting in lower fix success rates and larger location errors in areas with more rugged topography. The influence of topography and fix interval on location error and fix success rates may bias GPS location data, resulting in misclassification of habitat use and under-sampling certain areas used by animals. Location error and missing data can increase type II error and may result in incorrect inferences in some studies. These biases need to be assessed and steps should be taken to minimize their influence on results of studies of habitat selection and other aspects of animal ecology.

Potential Effects of the United States-Mexico Border Fence on Wildlife

Security infrastructure along international boundaries threatens to degrade connectivity for wildlife. To explore potential effects of a fence under construction along the U.S.-Mexico border on wildlife, we assessed movement behavior of two species with different life histories whose regional persistence may depend on transboundary movements. We used radiotelemetry to assess how vegetation and landscape structure affect flight and natal dispersal behaviors of Ferruginous Pygmy-Owls (Glaucidium brasilianum), and satellite telemetry, gene-flow estimates, and least-cost path models to assess movement behavior and interpopulation connectivity of desert bighorn sheep (Ovis canadensis mexicana). Flight height of Pygmy-Owls averaged only 1.4 m (SE 0.1) above ground, and only 23% of flights exceeded 4 m. Juvenile Pygmy-Owls dispersed at slower speeds, changed direction more, and had lower colonization success in landscapes with larger vegetation openings or higher levels of disturbance (p < or = 0.047), which suggests large vegetation gaps coupled with tall fences may limit transboundary movements. Female bighorn sheep crossed valleys up to 4.9 km wide, and microsatellite analyses indicated relatively high levels of gene flow and migration (95% CI for F(ST)=0.010-0.115, Nm = 1.9-24.8, M =10.4-15.4) between populations divided by an 11-km valley. Models of gene flow based on regional topography and movement barriers suggested that nine populations of bighorn sheep in northwestern Sonora are linked by dispersal with those in neighboring Arizona. Disruption of transboundary movement corridors by impermeable fencing would isolate some populations on the Arizona side. Connectivity for other species with similar movement abilities and spatial distributions may be affected by border development, yet mitigation strategies could address needs of wildlife and humans.

Responses of Desert Bighorn Sheep to Removal of Water Sources

Abstract In arid regions of the southwestern United States, water is often considered a primary factor limiting distribution and productivity of desert ungulates, including desert bighorn sheep (Ovis canadensis mexicana). Thus, wildlife management agencies and sportsmens organizations have invested substantial time and resources in the construction and maintenance of water catchments. Although the availability of freestanding water sources is believed to influence many aspects of the ecology of desert bighorn sheep, the efficacy of these water sources has been questioned and has not been examined experimentally. We used a before-after–control-impact study design to determine if removal of water catchments changed diet, characteristics of foraging areas used by female desert bighorn sheep, home-range size, movement rates, distance to catchments, adult mortality, productivity, or juvenile recruitment in 2 mountain ranges on the Cabeza Prieta National Wildlife Refuge, Arizona, USA. During pretreatment (2002–2003), we ensured that water catchments were available to desert bighorn sheep in both mountain ranges; during posttreatment (2004–2005), we drained all water catchments in the treatment range. We measured diet composition, characteristics of foraging areas, 50% and 95% kernel home ranges, movement rates, and distance to water catchments seasonally from 2002 to 2005. We also estimated adult survival, lamb:female, and yearling:female ratios from 2002 to 2005. We predicted that removal of water catchments would result in 1) increased use of foraging areas with more vegetation cover, more thermal cover, and higher succulent abundance; 2) increased consumption of cacti and other succulents; 3) an increase in home-range size, movement rates, and distance to nearest catchment; and 4) a decrease in adult survival, productivity, and juvenile recruitment. Removal of water catchments in the treatment range did not result in predicted changes in diet, foraging area selection, home-range size, movement rates, mortality, productivity, or recruitment. Female desert bighorn sheep did use areas with more thermal cover during the summer after removal of water catchments, but other characteristics of foraging areas used by bighorn sheep and their diet did not change appreciably with removal of water catchments. We did not document changes in home-range area, movement rates, or distance sheep were from water during hotter months; we only documented changes in home-range area, movement rates, and distance to water catchments during winter and autumn. There were 10 desert bighorn sheep mortalities in the treatment range and 8 in the control range; 7 mortalities in each mountain range were during pretreatment. Twelve of the 18 total mortalities occurred during summer. Survival rate was lower during pretreatment than posttreatment in both mountain ranges. We did not document increased mortality or a change in lamb:female or yearling:female ratios after removal of water catchments. Home-range area and movement rates declined with increasing precipitation. Annual survival rates increased with increases in the current years total precipitation and total precipitation during the previous year; annual survival rates declined with increases in average daily temperature during winter. There was a severe drought during pretreatment and abnormally wet conditions during posttreatment. The increase in precipitation that coincided with removal of water sources improved forage conditions during posttreatment and may have provided adequate water for female desert bighorn sheep. The lack of change in home-range size, movement rates, and distance to the nearest water catchment during hot, dry seasons after removal of water sources suggests that forage conditions played a greater role in determining home-range area and movement rates than did the presence of water catchments. Higher mortality rates during the drought of the pretreatment period indicates that during droughts as severe as that of 2002, presence of water catchments was not sufficient to prevent mortalities of desert bighorn sheep and a lack of forage quality and quantity was likely the primary limiting factor of the population during this time. Improving forage conditions during posttreatment, increases in forage moisture content, and availability of naturally occurring sources of free water in the treatment range likely minimized any impact of removing water catchments on survival rates and lamb:female and yearling:female ratios. However, due to the climatic conditions during the study we were unable to assess how the treatment population would have responded to a lack of water sources during a drought period. The influence of anthropogenic water catchments, if any, on desert bighorn sheep populations may be strongest during years with weather conditions that are neither drought nor wet periods. Given the high interannual variability in precipitation in many areas of the arid Southwest, it is important for wildlife managers to determine if and when water is the primary limiting factor for populations of desert bighorn sheep in order to make the most efficient use of agency time and resources.

Sonoran pronghorn use of anthropogenic and natural water sources

Abstract The Sonoran pronghorn (Antilocapra americana sonoriensis) is one of the most endangered ungulates in North America. The use of water to improve its habitat in southwestern Arizona has been limited in part because published reports claimed these desert ungulates do not use freestanding water. Because free-standing water has been beneficial to habitat improvement of other desert ungulates, we set up cameras at anthropogenic waters to see if they were used by pronghorn, examined literature and agency files related to Sonoran pronghorn and water, and interviewed ranchers who have lived and managed livestock in Sonoran pronghorn habitat since the 1930s regarding their observations of pronghorn use of livestock waters. Using direct observation and photographic evidence, we documented Sonoran pronghorn drinking freestanding water. Published reports claiming that Sonoran pronghorn do not drink were erroneous. Ranchers, agency files, and biologists from numerous state and federal agencies documented Sonoran pronghorn drinking. Federal and state agencies should be aggressive in examining how water developments can be used to assist in recovery of endangered Sonoran pronghorn.

Potential Foraging Decisions by a Desert Ungulate to Balance Water and Nutrient Intake in a Water-Stressed Environment

Arid climates have unpredictable precipitation patterns, and wildlife managers often provide supplemental water to help desert ungulates endure the hottest, driest periods. When surface water is unavailable, the only source of water for ungulates comes from the forage they consume, and they must make resourceful foraging decisions to meet their requirements. We compared two desert bighorn sheep (Ovis canadensis nelsoni) populations in Arizona, USA: a treatment population with supplemental water removed during treatment, and a control population. We examined whether sheep altered their seasonal diets without supplemental water. We calculated water and nutrient intake and metabolic water production from dry matter intake and forage moisture and nitrogen content, to determine whether sheep could meet their seasonal daily water and nutrient requirements solely from forage. Diets of sheep were higher in protein (all seasons) and moisture (autumn and winter) during treatment compared to pretreatment. During treatment, sheep diet composition was similar between the treatment and control populations, which suggests, under the climatic conditions of this study, water removal did not influence sheep diets. We estimated that under drought conditions, without any surface water available (although small ephemeral potholes would contain water after rains), female and male sheep would be unable to meet their daily water requirements in all seasons, except winter, when reproductive females had a nitrogen deficit. We determined that sheep could achieve water and nutrient balances in all seasons by shifting their total diet proportions by 8–55% from lower to higher moisture and nitrogen forage species. We elucidate how seasonal forage quality and foraging decisions by desert ungulates allow them to cope with their xeric and uncertain environment, and suggest that, with the forage conditions observed in our study area during this study period, providing supplemental water during water-stressed periods may not be necessary for desert bighorn sheep.

BEHAVIOR AND ACTIVITY BUDGETS OF SONORAN PRONGHORNS (ANTILOCAPRA AMERICANA SONORIENSIS)

Abstract Sonoran pronghorns (Antilocapra americana sonoriensis) have been listed as endangered since 1967, yet relatively little is known about their behavior. Knowledge of behavior is essential to understanding their ecology, but these data are difficult to obtain for Sonoran pronghorns due to land-use restrictions and large, inaccessible range. However, with establishment of a semi-captive breeding facility (260 ha) for Sonoran pronghorns in southern Arizona, behavioral studies are feasible. We studied diurnal activity budgets of six adult female Sonoran pronghorns during January–December 2005 by recording behavior (i.e., foraging, bedding, standing, traveling, other) with instantaneous sampling at 2-min intervals. We observed pronghorns on 148 days during the year for a total of 49,035 observations. Pronghorns exhibited seasonal and diurnal differences in activity budgets. Behavior was constrained by temperature in spring and summer, and by availability of forage in autumn. These data are the first regarding detailed behavior of Sonoran pronghorns and are valuable to their management and conservation by providing more information on constraints faced by the subspecies.

Introduction: management for the survival of Sonoran pronghorn in the United States

Wildlife Society Bulletin 2000, 28(4):5–xxx Peer refereed Historical population estimates of pronghorn (Antilocapra americana) in North America are as high as 60,000,000 (O’Connor 1939). In 2000 the population of pronghorn was estimated at 799,200 (Yoakum 2004). Currently there are 5 recognized subspecies of pronghorn based on differences in color, size, and form: American pronghorn (A. a. americana), Mexican pronghorn (A. a. mexicana), peninsular pronghorn (A. a. peninsularis), Oregon pronghorn (A. a. oregona), and Sonoran pronghorn (A. a. sonoriensis). However, recent genetic analyses have not revealed differences significant enough to retain these subspecies designations. Some suggest that a species decline is more legitimate than the 5 subspecies classified (Malone et al. 2002, O’Gara and Janis 2004). As genetic tools allow biologists to learn more about the genome of all species, classifications will evolve. However Sonoran pronghorn are eventually classified subspecifically, they will be protected under the Isolated Vertebrate Population Policy in the Endangered Species Act (United States Fish and Wildlife Service 1998). Current management of Sonoran pronghorn is also controversial (Paradiso and Nowak 1971, Cockrum 1981, United States Fish and Wildlife Service 1998, Malone et al. 2002, O’Gara and Janis 2004). The United States government listed Sonoran pronghorn as endangered in 1967. Since then, recovery efforts have been limited because much of Sonoran pronghorn habitat in the United States is inaccessible. Sonoran pronghorn historically ranged from eastern California into southeastern Arizona and south to Sonora, Mexico but are currently limited to <25% of their historical habitat in Arizona and northern Sonora, Mexico. Estimated numbers in the United States have been low since the early 1900s, ranging from approximately 100 in 1925 to <300 in 1998 (United States Fish and Wildlife Service 1998). However, during the current drought, numbers plummeted to <30 in 2002, and the subspecies was on the verge of extinction in the United States. The population of Sonoran pronghorn increased to <51 by December 2004 (J. C. deVos, Jr., Arizona Game and Fish Department, personal communication), but their survival is precarious and drastic and untested methods are ongoing to pull the subspecies from the brink of extinction. Aggressive management tactics including manipulation of forage and water availability and captive breeding have been initiated; efforts that some question. In the past decade, dedicated and determined individuals from the Arizona Game and Fish Department and the United States Fish and Wildlife Service initiated recovery efforts that had been proposed for nearly 3 decades. Those individuals (some of whom are authors and coauthors of the following papers) generated funds, interest,

Behavior and Timing Of Life-History Events In A Semi-Captive Population Of the Sonoran Pronghorn (Antilocapra americana sonoriensis)

Abstract The Sonoran pronghorn (Antilocapra americana sonoriensis) has been listed as endangered since 1967, yet little is known about its behavior due to difficulties observing them in the wild. During a study of Sonoran pronghorn in a semi-captive breeding facility in southern Arizona, we observed behaviors and timing of life-history events that have not been documented in peer-reviewed literature, including birth dates of fawns, pre-parturient and post-parturient behavior, timing of breeding season, behavior during the breeding season, date of horn casting by males, and response to predators. Behavior of the Sonoran pronghorn before and after parturition, during breeding, and toward predators was consistent with that reported for other subspecies. Timing of breeding, parturition, and horn casting all occurred earlier than reported for more northerly populations. Variation in timing of life-history activities was the main difference between the Sonoran pronghorn and other subspecies and would be expected due to the correspondence between seasonal rainfall and forage conditions in the Sonoran Desert and timing of parturition.

Desert Mule Deer Mortality and the Central Arizona Project

The Central Arizona Project (CAP) is one of the largest water delivery systems in the western United States. The CAP is a series of open canals that divert Colorado River water east to Phoenix, then south through Tucson, Arizona. Centra Arizona Project canals dissected over 250 km of desert mule deer (Odocoileus hemionus crooki) habitat. The canals are an attractive nuisance to deer. We documented deer mortality during 1979 to 1989 along 179 km of the CAP (formerly called the Granite Reef Aqueduct but renamed in 1989 as the Hay den-Rhodes Aqueduct [HRA]). Deer were entrapped in the canal during the construction years (1979–1987) or drowned when water was added in 1987; however, mortality was minimized when fencing was constructed. Deer managers and biologists should be aware of the effects of creating attractive nuisances in desert mule deer habitat and of the costs associated with minimizing mortality.

Forage Enhancement Plots as a Management Tool for Sonoran Pronghorn Recovery

Abstract We studied the efficacy of forage enhancement plots for Sonoran pronghorn (Antilocapra americana sonoriensis) during a drought in a large (130-ha) enclosure. As drought conditions continued, Sonoran pronghorn increased percent of time foraging in forage enhancement plots from 5.3 ± 2.2% (SE) to 47.8 ± 2.8% but showed signs of poor body condition and one died of starvation. Our results confirm the utility of forage enhancement plots for Sonoran pronghorn recovery, but suggest future research be conducted to determine the optimal size and watering regime of plots to increase survival and recruitment during prolonged droughts.