Gary C. Brundige

Effects of sample size on KERNEL home range estimates

Kernel methods for estimating home range are being used increasingly in wildlife research, but the effect of sample size on their accuracy is not known. We used computer simulations of 10-200 points/ home range and compared accuracy of home range estimates produced by fixed and adaptive kernels with the reference (REF) and least-squares cross-validation (LSCV) methods for determining the amount of smoothing. Simulated home ranges varied from simple to complex shapes created by mixing bivariate normal distributions. We used the size of the 95% home range area and the relative mean squared error of the surface fit to assess the accuracy of the kernel home range estimates. For both measures, the bias and variance approached an asymptote at about 50 observations/home range. The fixed kernel with smoothing selected by LSCV provided the least-biased estimates of the 95% home range area. All kernel methods produced similar surface fit for most simulations, but the fixed kernel with LSCV had the lowest frequency and magnitude of very poor estimates. We reviewed 101 papers published in The Journal of Wildlife Management (JWM) between 1980 and 1997 that estimated animal home ranges. A minority of these papers used nonparametric utilization distribution (UD) estimators, and most did not adequately report sample sizes. We recommend that home range studies using kernel estimates use LSCV to determine the amount of smoothing, obtain a minimum of 30 observations per animal (but preferably >50), and report sample sizes in published results.

Elk and hunter space-use sharing in South Dakota.

Documenting space-use patterns of elk (Cervus elaphus) and hunters is important for determining whether disturbance by hunters affects elk movements and resource use. We compared utilization distributions of elk and hunters during 4 hunting seasons (early archery, trophy rifle, antlerless rifle, and late archery) from 1993 to 1996 in the southern Black Hills, South Dakota, using the Volume of Intersection Index statistic. Volume of Intersection Indices were used as the response variable in a general linear regression model analysis to determine if environmental features were correlated with measures of space-use sharing. Space-use sharing for cow elk and hunters was lowest during the late archery hunt and highest during the trophy rifle and early archery seasons. Space-use sharing was lowest for bull elk and hunters during the trophy rifle hunt and highest during the early archery season. Hunter density, secondary road use, and tertiary road density were negatively correlated with space-use sharing. In contrast, vegetative cover was positively correlated with space-use sharing. Subherds occupying areas dominated by overstory-killed habitat exhibited less overlap with hunters than subherds residing in more heavily forested habitats. These results suggested that control of hunter density, including limitation of road access, in areas which lack vegetative cover may help mitigate hunter disturbance of elk. Variation in elk movements and environmental features correlated with overlap measures indicated that elk response to hunters was adaptive and short-lived.

Validation tests of a spatially explicit habitat effectiveness model for Rocky Mountain elk

We tested the validity of a spatially explicit habitat effectiveness model for Rocky Mountain elk (Cervus elaphus nelsoni). The model scored habitat effectiveness based on seasonal changes in the quality, quantity, and availability of forage. Seasonal forage potential scores were derived by integrating information on existing vegetation, site potential, historic disturbances, topography, and roads. The model generated maps of seasonal habitat effectiveness that were used to create utilization distributions (UD; i.e. 3-dimensional density estimates). We tested the elk habitat model using telemetry data collected on 5 cow elk sub-herds from 1993 to 1997 in Custer State Park (CSP), South Dakota, USA. We computed fixed kernel UD from elk telemetry data and simulated random UD within the confines of each sub-herd boundary. The degree of fit between elk UD and model predicted UD (elk-model UD) and random UD and model predicted UD (random-model UD) was represented by sub-herd, season, and year using the Volume of Intersection test statistic (V.I. Index). There were no differences in V.I. Indices by year for elk-model (1993 = 0.59, 1994 = 0.54, 1995 = 0.60, 1996 = 0.57, 1997 = 0.57; F 4,70 = 0.93, P = 0.45) or random-model (1993 = 0.59, 1994 = 0.55, 1995 = 0.59, 1996 = 0.58, 1997 = 0.59; F 4,70 = 1.49, P = 0.21) UD; thus, V.I. Indices were pooled across years. Two-way analysis of variance indicated that elk-model V.I. Indices did not differ by sub-herd (B = 0.50, Y = 0.58, A = 0.56, S = 0.58, R = 0.63; F 4,12 = 2.68, P = 0.08), season (Spring = 0.55, Summer = 0.55, Fall = 0.60, Winter = 0.58; F 3,12 = 0.80, P = 0.52), or the interaction terms (B Spring = 0.48, B Summer = 0.52, B Fall = 0.52, B Winter = 0.49, Y Spring = 0.60, Y Summer = 0.52, Y Fall = 0.58, Y Winter = 0.62, A Spring = 0.47, A Summer = 0.58, A Fall = 0.64, A Winter = 0.54, S Spring = 0.54, S Summer = 0.49, S Fall = 0.64, S Winter = 0.65, R Spring = 0.70, R Summer 0.64, R Fall = 0.60, R Winter = 0.59; F 12,55 = 1.68, P = 0.10). V.I. Indices for random-model UD did not differ by season (Spring = 0.58, Summer = 0.57, Fall = 0.58, Winter = 0.59; F 3,12 = 0.56, P = 0.65) or interaction term (B Spring = 0.55, B Summer = 0.58, B Fall = 0.56, B Winter = 0.54, Y Spring = 0.57, Y Summer = 0.53, Y Fall = 0.53, Y Winter = 0.57, A Spring = 0.61, A Summer = 0.63, A Fall = 0.63, A Winter = 0.64, S Spring = 0.60, S Summer = 0.49, S Fall = 0.57, S Winter = 0.59, R Spring = 0.59, R Summer 0.60, R Fall = 0.60, R Winter = 0.59; F 12,55 = 1.44, P = 0.17); however, differences were noted among sub-herds (B = 0.56, Y = 0.55, A = 0.63, S = 0.56, R = 0.60; F 4,12 = 4.48, P = 0.02). V.I. Indices for elk-model UD differed from random-model UD (F 4,12 = 4.71, P = 0.02); model performance was worse than random (i.e., lower V.I. Indices) for 2 sub-herds (elk-model sub-herd B = 0.50 vs. random-mode sub-herd B = 0.56 and elk-model sub-herd A = 0.56 vs. random-model sub-herd A = 0.63). Lower V.I. Indices were observed for 2 sub-herds that occupied areas recently subjected to large-scale wildfires. For sub-herds not subjected to fire effects (i.e., greater loss of vegetation security cover), the model portrayed elk habitat use less consistently, as represented by greater variability (27-42% larger standard errors) in V.I. Indices, during summer. Conversely, the model portrayed elk habitat use most consistent for the same 3 sub-herds during fall.

Summer Bed Sites of Elk (Cervus elaphus) in the Black Hills, South Dakota: Considerations for Thermal Cover Management

Abstract We characterized 131 summer, diurnal bed sites of 26 elk (11 bulls and 15 cows) in Custer State Park, South Dakota, from 5 June–30 August 1994, 1995 and 1996. Overstory canopy closure, number and basal area of trees, percent litter and bare ground were greater (P < 0.05) at bed sites than at random plots. North aspects were selected (P < 0.05). Microsite air temperature and percent of grass were lower (P < 0.05) at bed sites than at random plots. Hiding cover, wind speed, percent of forbs, shrubs, rocks, and wood, slope percent, average tree dbh, elevation, distance to roads, distance to trails, and distance to water were not different between bed sites and random plots (P > 0.05). Trees were present at 128/131 (97.7%) of bed sites (0.01 ha square plot), but occurred on only 41.2% (54/131) of random plots. An average summer, diurnal elk bed site had basal area >12.4 m2/ha, >110 trees/ha, >54% canopy closure on N aspects. Overstory canopy closure, tree basal area and microsite temperature correctly classified 86.2% of the observations, suggesting thermoregulatory factors influenced CSP elk use of summer, diurnal bed sites. Although elk are successful in some unforested areas despite the lack of suitable thermal cover, our data suggest that elk in the Black Hills prefer relief sites that provide thermal bed sites when available during the summer diurnal period. Management of appropriate thermal cover should be maintained in areas in which it exists.

Immobilization of Rocky Mountain Elk with Telazol® and Xylazine Hydrochloride, and Antagonism by Yohimbine Hydrochloride

Ten trapped Rocky Mountain elk (Cervus elaphus nelsoni) were successfully immobilized with a combination of 500 mg Telazol® and 60 mg xylazine hydrochloride (HCl) from 9 July to 25 August 1993 in Custer State Park, South Dakota (USA). Mean (SD) dosages of 2.5 (0.6) mg/kg Telazol® and 0.3 (0.1) mg/kg xylazine HCl, respectively, were administered, resulting in a mean (SD) induction time of 4.6 (0.8) min. Induction time varied with weight and dosage. Respiratory rate (breaths/ min) increased following injection of Telazol® and xylazine HCl and remained elevated or continued to increase through 10 min post-injection and then declined. There were no mortalities in this study. Forty mg of yohimbine HCl was used as an antagonist in eight elk, resulting in a mean (SD) recovery time of 14.0 (9.9) min when administered intravenously (n =6), and 124.7 (9.5) min when given intramuscularly (n = 2). Recovery time varied with weight and dosage of yohimbine. Elk given 2.1 to 2.6 mg/kg Telazol® and 0.1 to 0.3 mg/kg xylazine HCl responded to yohimbine HCl when administered intravenously.

Herd organization of cow elk in Custer State Park, South Dakota

Abstract Understanding herd organization is important when considering management alternatives designed to benefit or manipulate elk (Cervus elaphus) populations. We studied the seasonal and annual herd organization of cow elk in Custer State Park, South Dakota from 1993–1997 by examining seasonal subherd range size, spatial arrangement, overlap, and site fidelity. Based on social interaction analyses, we combined locations of radiocol-lared cow elk to delineate subherds. We computed 95% kernel home ranges with least-squares cross validation for each subherd by season and year. Subherd overlap and fidelity by season and year were computed using the Volume of Intersection Index (VI) statistic. We identified 5 relatively discrete, resident cow–calf subherds. We observed little overlap in utilization distributions of adjacent subherds. The mean VI score across all subherds and time points (n=140) was 0.06 (SE=0.009), indicating an average 6% overlap in subherd area utilization. Subherd overlap between pairs was 0.08 in fall (SE= 0.021), 0.06 in winter (SE=0.018), 0.06 in spring (SE=0.2), and 0.05 in summer (SE= 0.016). Range sizes were not different between any pairs of seasons or years (F13,52=0.7, P=0.75). Subherd fidelity ranged from 0.41 (SE=0.033) to 0.60 (SE=0.018) overall, indicating differential use within the subherd boundary across years. The ability to distinguish discrete cow–calf subherd units is consistent with other studies and may aid elk management in Custer State Park. However, use patterns within subherd boundaries were inconsistent across years and may reflect human disturbances (e.g., hunting and logging activities), differences in our sampling approach, or changes in matriarchal leadership. Further evaluation into factors affecting space-use patterns is necessary to predict changes in range use within the subherd boundary.

RELATIONSHIPS AMONG FECAL LUNGWORM LOADS, FECAL GLUCOCORTICOID METABOLITES, AND LAMB RECRUITMENT IN FREE-RANGING ROCKY MOUNTAIN BIGHORN SHEEP

Most wild Rocky Mountain big-horn sheep (Ovis canadensis canadensis) in northern latitudes are infected with lungworms. Indirect effects of lungworms on bighorn sheep are unknown, but high pulmonary burdens might increase stress (i.e., elevated glucocorticoid levels), and chronic stress could in turn decrease fitness. We hypothesized that high lungworm burdens in Rocky Mountain bighorn ewes increase stress, thereby increasing lamb mortality. To test our hypothesis, one subherd of bighorn sheep in Custer State Park, South Dakota was provided a free-choice loose mineral mix containing the anthelmintic fenbendazole every six weeks from March 1999 to August 2000 to eliminate lungworms; another subherd served as the control. Daily, individually marked ewes were located telemetrically from the ground and uniquely marked animals were observed until they defecated. After the herd moved from the area, fecal samples were collected and stored at −23 C. A consistent number of samples per season per herd (x̄=16.56±3.99 samples) were collected. =Fecal larval lungworm levels (LPG) in the treatment subherd were lower than levels in the control subherd; however, there was no difference in fecal glucocorticoid metabolite (FGM) levels between the two subherds. Fecal glucocorticoid metabolite levels varied by season in both subherds, with levels in winter lower than during the other three seasons. Lamb:ewe ratios were not different between the control and treatment subherds at the end of summer 1999. In contrast, the treatment group had a lower lamb:ewe ratio at the end of summer 2000 despite having lower LPG. However, this result was attributed to lower ewe production, not lower lamb survival. The LPG levels were not correlated with FGM concentrations; instead, FGM levels might reflect normal seasonal patterns. Other factors, including contagious ecthyma, were more important for determining lamb mortality than LPG and FGM levels during our study. We suggest further experimental work over a longer duration to address these relationships.

Early Pregnancy Determination Using Serum Progesterone Concentration in Bighorn Sheep

We determined serum progesterone concentrations of 25 female bighorn sheep (Ovis canadensis) in February 1984 and January 1985 as an indicator of pregnancy. Accuracy in predicting pregnancy was 90% in 1984, 80% in 1985, and 84% over both years. Most misclassifications were attributed to sampling too close to estrous. Accuracy may be improved if sampling occurs >16 days after the conclusion of breeding activity. Serum progesterone concentration is an accurate indicator of early pregnancy in bighorn sheep. J. WILDL. MANAGE. 52(4):610-612 Detection of pregnancy early in gestation is required to accurately determine reproductive rates and estimate early prenatal loss. Several techniques are used for pregnancy determination of domestic animals; some have been used successfully for wild animals (e.g., rectal palpation [Greer and Hawkins 1967, Follis and Spillet 1974], laparotomy [Zwank 1981], ultrasound [Smith and Lindzey 1982, Harper and Cohen 1985], and hormonal assay [Ramsay and Sadleir 1979, Whitehead and McEwan 1980]). Blood progesterone concentrations have been shown to be accurate indicators of pregnancy in domestic (Bassett et al. 1969) and bighorn females (Ramsay and Sadleir 1979, Whitehead and McEwan 1980). Progesterone determination has the advantage of relatively simple sample collection (if animals can be trapped and handled) and relatively inexpensive analysis. Our study was designed to determine if progesterone serum concentrations indicated early pregnancy in free-ranging bighorn sheep. Serum progesterone concentrations were assayed by B. Pettitjean (Anim. Sci. Dep., South Dakota State Univ.). We thank Custer State Park (CSP) personnel and students from South Dakota State University for assistance with trapping. Funding was provided by a grant from the Foundation for North American Wild Sheep, Custer State Park, and federal aid administered by South Dakota Department of Game, Fish and Parks.

Adult Pronghorn (Antilocapra americana) Survival and Cause-specific Mortality in Custer State Park, S.D

Abstract Although understanding natural mortality rates of ungulate populations is essential for effective management, published data on adult survival from unharvested pronghorn (Antilocapra americana) populations in the Northern Great Plains is limited. We estimated seasonal adult survival rates and cause-specific mortality of an unharvested pronghorn population in Custer State Park, S.D. We assessed the relative importance of sex, age, year, and season in explaining pronghorn survival rates using an information-theoretic approach. We captured and radio-collared 26 male and 24 female adult pronghorn from fall 2005 through spring 2008. We observed higher predation rates and lower survival of adult pronghorn in CSP compared to other populations in the region, but similar to the pronghorn population in Yellowstone National Park. We documented 23 deaths (10 females, 13 males) of the 50 radio-collared pronghorn from Nov. 2005–Nov. 2008. Predation by mountain lions (Puma concolor) and coyotes (Canis latrans) accounted for 69.5% of all mortalities. The season model received the greatest support although there also was strong support for the season × sex model. Seasonal survival for males and females was >0.90 for the winter-grouping and breeding seasons but fell to 0.791(95% CI 0.644–0.887) and 0.837 (95% CI 0.706–0.916) for females and males, respectively, during the small group – parturition season. A dense predator population, as well as a higher vulnerability to predation when pronghorn are solitary or in small groups, may explain the lower survival during these time periods. If population estimates fall below management goals, management actions aimed at reducing predator cover may be beneficial to adult pronghorn. Managers of pronghorn populations near forested and rugged areas and that are sympatric with dense predator populations should consider adult survival may be lower than observed in Great Plains populations.

Extended Duration of Parturition Season in North American Elk (Cervus Elaphus)

Abstract The timing of births in ungulates has significant implications for juvenile survival and population growth. For North American elk (Cervus elaphus), typical parturition season ranges from late May to early Jun., and juveniles born outside of this peak characteristically exhibit lowered survival. We observed abnormally long parturition seasons in free-ranging elk populations in Missouri and South Dakota during 2012. Both populations exhibited late births; the last known births occurred on 26 Sep. in Missouri and 4 Sep. in South Dakota. Duration of parturition season was 112 and 119 d in Missouri and South Dakota, respectively. In Missouri, late births likely resulted from breeding by both yearling females and males. Late parturition in South Dakota may be caused by extended estrous cycles of elk that occurred on high quality range where few adult males were located.