J. Range Manage. 53: 479–482 September 2000 Effects of roundups on behavior and reproduction of feral

KYLE V. HANSEN AND JEFFREY C. MOSLEY

Abstract Resumen

Roundups are used to maintain feral populations in bal- Las redadas se utilizan para mantener las poblaciones de ance with rangeland capacity, but little is known about caballos silvestres en balance con la capacidad de apacentamien- short-term and long-term effects of roundups on horses. We eval- to, pero poco se sabe acerca de los efectos a corto y largo plazo uated the effects of roundups on behavior and reproduction of de las redadas en los caballos. Evaluamos el efecto de las redada feral horses. The study was conducted near Challis, Ida. during en el comportamiento y reproducción de los caballos silvestres. 1994–1995, and repeated near Lander, Wyo. during 1995–1996. El estudio se condujo cerca de Challis, Ida. durante 1994 y 1995 Horses were randomly assigned to 3 different treatment groups. y se repitió cerca de Lander Wyo. durante 1995 y 1996. Los One group (ADOPTED) was gathered by a Bureau of Land caballos se asignaron aleatoriamente a tres grupos de tratamien- Management roundup crew using a helicopter. These horses to. Un grupo (ADOPTADO) fue reunido y removido por una were removed and placed in the Adopt-A-Horse Program. The cuadrilla de redadas del Buro de Manejo de Tierras la cual uti- second group (SIMULATED) consisted of horses that were gath- lizó un helicóptero. Estos caballos fueron después colocados en el ered by helicopter, but these horses evaded capture and programa "Adopta un Caballo". El segundo grupo, (SIMULA- remained in the study area after the roundup. Horses in the third DO) consistio de caballos que fueron reunidos con helicóptero, group (CONTROL) were not herded by helicopter. Horse behav- pero estos caballos evadieron la captura y permanecieron en el ior was monitored in the SIMULATED and CONTROL groups área de estudio después de la redada. El tercer grupo (CON- before and after roundups. Behavioral variables analyzed were TROL), fueron caballos que no se pastorearon con helicóptero. the percentage of time spent resting, feeding, vigilant, traveling, El comportamiento de los caballos se monitoreo en los grupos and engaged in agonistic encounters. Neither foraging or social SIMULADO y CONTROL antes y después de las redadas. Las behavior of feral horses was affected by roundups in either study variables de comportamiento se analizadas fueron el porcentaje area (P > 0.10). Reproduction was monitored within the SIMU- de tiempo utilizado en descanso, alimentación, vigilancia, viajar, LATED, CONTROL, and ADOPTED groups during the year y encuentros agonísticos. Las redadas no afectaron ni el compor- following roundups. The percentages of with live did tamiento de alimentación ni el comportamiento social de los not differ (P > 0.10) among the 3 treatment groups in Idaho or caballos salvajes en el área de studio (P > 0.01). Al año siguiente Wyoming. Foaling success rates in Idaho were 29%, 31%, and de las redadas se monitoreo la reproducción dentro de los grupos 43% for CONTROL, ADOPTED, and SIMULATED mares, SIMULADO, CONTROL y ADOPTADOS. El porcentaje de respectively. In Wyoming, foaling success rates were 29%, 42%, yeguas con potros vivos no difirió entre los tres tratamientos and 48% for CONTROL, ADOPTED, and SIMULATED (P>0.10) y los resultados fueron similares en Idaho y Wyoming. groups, respectively. We found no evidence that roundups had Las tasas de potros vivos en Idaho fueron 29%, 31% y 43% para deleterious effects on behavior or reproduction of feral horses. los tratamientos CONTROL, ADOPTADO y SIMULADO respectivamente. En Wyoming los porcentajes de potros vivos fueron 29%, 42% y 48% para lostratamientos CONTROL, Key Words: wild horses, caballus, A d o p t - A - H o r s e ADOPTADO y SIMULADO respectivamente. No encontramos Program, foraging behavior, social behavior evidencia de que las redadas tuvieran un efecto nocivo en el com- portamiento o la reproducción de los caballos salvajes. About 46,000 feral horses (Equus caballus) live in the western United States (USDI-BLM and USDA-FS 1993). The Wild Free- Roaming Horse and Burro Act, Public Law 92-195 (U.S. Code causing rangeland degradation (Smith 1986). Roundups remove 1988), obligates the Bureau of Land Management (BLM) and the excess animals, after which horses are placed in private owner- U.S. Forest Service to protect feral horses on public lands of the ship via the Adopt-A-Horse Program. Roundups obviously dis- western United States from unauthorized capture or killing. These turb the daily routine and behavior of feral horses, but little is agencies must also maintain these populations in balance with known about short-term and long-term effects of roundups on rangeland carrying capacity (USDI-BLM and USDA-FS 1993). horses. When perturbations occur, horses may shift their behavior Uncontrolled horse populations lead to excessive grazing, in turn to minimize the effects. For example, feral horses alter their habi- tat use to seek refuge from biting insects (Keiper and Berger 1982). Behavioral responses to perturbations also may include Authors wish to thank Kendall Johnson, Gordon Woods, Carl Hunt, and BLM increased time spent in agonistic encounters with other horses, personnel in Idaho and Wyoming, in particular Mike Courtney, Roy Packer, and Phyllis Stark, for their assistance. such as when mares enter new areas and encounter resident mares Manuscript accepted 5 Dec. 1999. (Tyler 1972). Perturbations may also induce stress that decreases

JOURNAL OF RANGE MANAGEMENT 53(5), September 2000 479 reproduction. For example, forced copula- vations and Douglas-fir/Idaho fescue at istics of each horse were recorded to aid tion by invading males may induce abor- the highest elevations (BLM-SCS 1979). their identification. In Idaho, the SIMU- tion in females unprotected by their resi- LATED, CONTROL, and ADOPTED dent (Berger 1983), and abortions Wyoming Study Area groups totaled 14, 14, and 39 mares, may occur in response to male harassment The Wyoming study area was in respectively. In Wyoming, there were 33, or other stresses imposed by changes in a Muskrat Basin, 202-km2 of public land 14, and 34 mares, respectively, in the herd’s social structure (Berger 1983). The administered by the BLM, located SIMULATED, CONTROL, and ADOPT- purpose of this study was to document the between State Highways 789 and 136. ED groups. In each study area the roundup effects of roundups on the foraging behav- Vegetation was dominated by Wyoming and simulated roundup occurred the same ior, social behavior, and reproductive suc- big sagebrush, bluebunch wheatgrass, day, on 27 August 1994 in the Idaho study cess of feral horses. Our specific null western wheatgrass, Sandberg bluegrass, area and 13 August 1995 in Wyoming. hypotheses were: 1) behavior does not dif- Idaho fescue, and needle-and-thread grass fer between horses rounded up and horses (Stipa comata Trin. & Rupr.). Elevations Horse Behavior not rounded up; and 2) reproductive suc- ranged from 1,820–2,100 m. Annual pre- Horse behavior was monitored in the cess does not differ among horses rounded cipitation averages 25 cm with about 50% SIMULATED and CONTROL groups for up, horses not rounded up, and horses occurring during May and June, and 50% 3 weeks immediately before and 3 weeks placed in the Adopt-A-Horse Program. occurring during November through after the simulated roundups. Monitoring March in the form of snow (Perrich 1992). before the simulated roundup occurred Soils were a loamy-skeletal, mixed (cal- from 25 July through 26 August 1994 on Study Area careous), frigid, shallow Ustic the Idaho study area and 10 July through Torriorthent (Cragosen) in most of the 12 August 1995 for the Wyoming area. The study was conducted in 2 separate area, and a fine, montmorillonitic Borollic Data following the simulated roundup was areas, one in central Idaho about 3 km Paleargid (Milren) on the lower sites. collected from 28 August through 20 southwest of Challis, Ida., and one in cen- The dominant range site for this study September 1994 for the Idaho area and 14 tral Wyoming about 32 km north of area was Loamy (24–35 cm precipitation) August through 28 August 1995 for the Jeffrey City, Wyo. with associated range sites of Shallow Wyoming area. Behavioral observations Sandy (24–35 cm precipitation) and Sandy spanned more than 600 hours during each Idaho Study Area (25–35 cm precipitation) (Soil Conservation year of the study. Service 1988). We recorded the percentage of time that The Idaho study area was 150-km2 o f a band of horses spent in the following public land administered by the BLM, activities: feeding (primarily grazing with located north of Spar Canyon Road, east little or no travel other than to move to a of State Highway 75, and west of U.S. Methods new feeding station); resting (both recum- Highway 93. Elevations ranged from bent and standing); traveling (including 1,675–2,745 m. Annual precipitation aver- This experiment was conducted in Idaho incidental grazing while walking); aggres- ages 18 cm, with about 50% occurring as from July 1994 to July 1995 and in sion within the band (defined as threat snow during November through March Wyoming from July 1995 to July 1996. postures, striking with the feet, or biting); (Perrich 1992). Major plant species pre- Field procedures and statistical methods aggression between bands; and vigilance sent were bluebunch wheatgrass were identical for both study areas. (head and neck erect, ears forward, active- (Agropyron spicatum (Pursh.) Scribn. & ly looking around). Data were recorded Smith), western wheatgrass (A g r o p y r o n Roundups every 10 minutes during 4-hour observa- smithii Rydb.), Sandberg bluegrass (P o a Horses in each study area were random- tion periods using instantaneous scan sam- s a n d b e r g i i Vasey), Idaho fescue (F e s t u c a ly assigned to 3 different treatment groups. pling (Altmann 1974). Each band of hors- i d a h o e n s i s Elmer), and Wyoming big One group (ADOPTED) was gathered by es was observed 3 times before and 3 sagebrush (Artemesia tridentata wyomin - a BLM roundup crew using a helicopter. times after the simulated roundups, with g e n s i s Beetle & Young). Limber pine These horses were removed and placed in one of the 3 observation periods each (Pinus flexilus James), Douglas-fir the Adopt-A-Horse Program. The second occurring in early morning (0700–1100 (Pseudotsuga menziesii (Mirb.) Franco) group (SIMULATED) consisted of horses hours), mid-day (1100–1500 hours), and and curlleaf mountain mahogany that were gathered by helicopter, but these early evening (1500–1900 hours). (Cercocarpus ledifolius Nutt. ex. Torr. & horses evaded capture and remained in the Gray) occurred at higher elevations within study area after the roundup. Horses in the the study area. third group (CONTROL) were not herded Reproduction Soils ranged from a loamy-skeletal, by helicopter. In the Idaho study area, the Adopted Groups. A veterinarian drew 10 ml of blood from each in the mixed frigid Xerollic Haplargid ADOPTED, SIMULATED, and CON- ADOPTED groups. These 10-ml samples (Dawtonia) at the lower elevations to a TROL groups were composed of 12, 3, were immediately frozen, and later in the loamy skeletal, mixed Calcic Cryoborol and 4 bands (i.e., social subgroups) of laboratory blood serum was separated (Gany) at the highest elevations. The dom- horses, respectively. The number of bands from plasma. Blood serum samples were inant range site for the study area was in the ADOPTED, SIMULATED and then sent to the Veterinary School at the Gravelly Loamy (20–30 cm precipitation) CONTROL groups in Wyoming were 10, University of California-Davis for analy- with associated range sites of Gravelly 8, and 5, respectively. Bands contained 2 Loam (33–40 cm precipitation) and sis. Mares were considered pregnant if to 10 adult horses, and all bands were pho- estrogen blood serum levels were 7 ng/ml Flagstone (20–28 cm precipitation). The tographed to document their membership. habitat type was Wyoming big sage- or greater and progesterone levels were 6 Individual members of each band were ng/ml or greater. In July of the year fol- brush/bluebunch wheatgrass at lower ele- also photographed, and physical character-

480 JOURNAL OF RANGE MANAGEMENT53(5), September 2000 lowing roundups, each adopter of a mare Table 1. Mean percentage (±SE) of time that bands of feral horses spent in each behavioral activity was sent a questionnaire asking for foaling following simulated roundups. information. Non-respondents were con- tacted in a follow-up survey by telephone. Idaho Site Wyoming Site A 100% response rate was achieved. Activity Simulated Control Simulated Control Simulated and Control Groups. H o r s e s ------(%) ------1 in the SIMULATED and CONTROL Vigilance 12.9 ± 0.8a 8.3 ± 0.4a 1.3 ± 0.7a 1.8 ± 0.9a groups were observed about 10 months Feeding 58.5 ± 17.3a 71.4 ± 9.4a 46.9 ± 5.9a 38.0 ± 5.3a Traveling 24.0 ± 17.0a 17.4 ± 10.la 5.5 ± l.7a 18.7 ± 3.8a after the roundups. The number of mares Resting 4.6 ± 3.0a 2.9 ± 2.0a 46.1 ± 6.4a 41.3 ± 0.1a and foals in each band was counted on 30 Aggression within bands 0.0 ± 0.0a 0.0 ± 0.0a 0.0 ± 0.0a 0.0 ± 0.0a June and 1 July 1995 on the Idaho site and Aggression between bands 0.0 ± 0.0a 0.0 ± 0.0a 0.1 ± 0.0a 0.2 ± 0.0a 1 July through 5 July 1996 on the 1Within each study area, values within rows followed by the same lowercase letter are not different (P > 0.10). Wyoming site.

Statistical Analysis Results monal changes induced by stressful condi- A completely random experimental tions (Traub-Dargatz et al. 1988, Baucus design was used. Data from the Idaho and Horse Behavior et al. l990a, 1990b, Colburn et al. 1991, Wyoming sites were analyzed separately. Individually, none of the behavioral Ferlazzo et al. 1991, Wong et al. 1992). All differences were considered signifi- variables differed between SIMULATED Similarly, in our study roundups did not cant at P £ 0.10. For the behavioral data, a and CONTROL treatments in either study decrease reproductive rates of feral horses. band of horses was the experimental unit. area (Table 1). Multivariate analyses also Foaling rates of the SIMULATED, CON- Individual horses within the bands were found no differences between the SIMU- TROL, and ADOPTED mares all com- subsamples. Behavioral data were trans- LATED and CONTROL groups in either pared favorably with a 10-year average of formed using arcsine transformation to the Idaho study area (P = 0.67) or the 35% documented within a herd meet conditions for normality. Each Wyoming study area (P = 0.58). in Montana (Garrott and Taylor 1990). behavioral variable (feeding, resting, trav- The ADOPTED mares experienced the eling, aggression within the band, aggres- most perturbation but had an overall - sion between bands, and vigilance) was Reproduction ing rate of 33%. analyzed using analysis of covariance The percentage of mares with live foals Feral horses in our study apparently (Johnson and Wichern 1992). did not differ (P > 0.10) among the 3 treat- adapted easily to any stress caused by Observations collected before the simulat- ments in either study area. By July 1995 in roundups. We found no evidence that ed roundups were the covariables (e.g., the Idaho study area, 29%, 31%, and 43% roundups had deleterious effects on behav- vigilance before the simulated roundups of the mares had live foals in the CON- ior or reproduction of feral horses. was the covariable when analyzing vigi- TROL, ADOPTED, and SIMULATED lance after the simulated roundups). Data groups, respectively. In the Wyoming were then analyzed collectively using mul- study area, by July 1996 the percentage of Literature Cited tivariate analyses. Data from the mares with live foals in the CONTROL, Wyoming site were analyzed using multi- ADOPTED, and SIMULATED groups variate analysis of covariance (MANCO- was 29%, 42%, and 48%, respectively. Altmann, J. 1974. Observational study of behav- ior: Sampling methods. Behav. 49:227–265. VA). Dependent variables in the MAN- At the time of roundup, 27 of 39 mares (69%) were pregnant in the Idaho Baucus, K.L., S.L. Ralston, C.F. Nockels, A.O. COVA were the behavioral variables vigi- McKinnon, and E.L. Squires. 1990a. E f f e c t s lance, feeding, traveling, resting, and ADOPTED group, and 18 of 34 mares of transportation on early embryonic death in aggression between bands following the (53%) were pregnant in the Wyoming mares. J. Anim. Sci. 68:345–351. simulated roundup. The independent vari- ADOPTED group. Successful pregnancies Baucus, K.L., E.L. Squires, S.L. Ralston, A.O. able used was group (i.e., SIMULATED numbered 12 of 27 (44%) and 14 of 18 McKinnon, and T.M. Nett. 1990b. Effects of or CONTROL). Covariables used were (77%) for Idaho and Wyoming ADOPT- transportation on the and concen- vigilance, feeding, traveling, resting and ED groups, respectively. trations of in mares. J. Anim. Sci. aggression between bands before the sim- 68:419–426. ulated roundup. For the Idaho site there Berger, J. 1983. Induced abortion and social fac- tors in wild horses. Nature 303:59–61. were too few degrees of freedom to allow Discussion and Conclusions BLM-SCS (Bureau of Land Management-Soil the observations before the simulated Conservation Service). 1979. Range site roundup to be used as covariables, so Roundups did not increase agonistic descriptions. B12. March 1979. Internal, these data were analyzed using multivari- behavior among feral horses, nor did Boise,Ida. ate analysis of variance. Aggression with- roundups cause feral horses to reallocate Colburn, D.R., D.L. Thompson, Jr., T.L. Roth, in the band was not used as a variable or their time spent in various daily activities. J.S. Capehart, and K.L. White. 1991. covariable in the multivariate analyses Responses of and prolactin to sexual Feral horses in our study allocated their because no agonistic encounters within excitement and stress in and . time similarly to undisturbed free-roaming bands were recorded. J. Anim. Sci. 69:2556–2562. horses in southern France (Duncan 1980), The percentage of mares with live foals Crane, K.K., M.A. Smith, and D. Reynolds. western Alberta (Salter and Hudson 1979), in the SIMULATED, CONTROL, and 1997. Habitat selection patterns of feral horses and central Wyoming (Crane et al. 1997). in south central Wyoming. J. Range Manage. ADOPTED groups was compared with Feeding was the primary activity. 50:374–380. chi-square analysis (Johnson and Wichern Duncan, P. 1980. Time budgets of Camargue 1992). Domestic horses are usually able to maintain their pregnancies despite hor- horses. II. Time budgets of adult horses and weaned sub-adults. Behavior 72:26–49.

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