Temporal Overlap Among Feral Horses, Cattle, and Native Ungulates at Water Sources

Abstract

Feral horse (Equus ferus caballus) populations on public rangelands in the western United States threaten forage production for livestock and wildlife habitat. Interference competition between feral horses and heterospecifics at watering sources can have negative effects on livestock and wildlife. Researchers have documented altered timing and behavior of wild ungulates at water sources when horses were present. The few studies examining these interactions have infrequently occurred within areas specifically managed for feral equids and have not occurred in sites with cattle. We used motion-sensitive cameras at 8 watering sources to document watering activity patterns and construct indices of temporal overlap among feral horses, cattle, elk (Cervus canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana) within the Adobe Town Herd Management Area in southern Wyoming, USA, between June and September 2018 and 2019. Feral horses, cattle, and pronghorn exhibited a high degree of temporal overlap (>79%) in water use, with feral horses and pronghorn exhibiting the highest estimated percent overlap (88.1%, 95% CI = 86.5-89.6%). Mule deer and elk watering activity also overlapped with horses and cattle but to a lesser degree (<55%). Feral horses spent a mean of 16.7 ± 30.5 (SD) minutes during a watering event and were present at a given water source on average 4.5 ± 6.3% and up to 34.9% of the day, which is less than reported in previous studies. Cattle spent on average 23.5 ± 44.9 minutes during a watering event, and were present on average 4.2 ± 7.7% and up to 42.4% of the day at a single water source. Results of generalized linear mixed-effects models indicated that number of conspecifics was the strongest predictor of visit duration for pronghorn and horses; hour of the day and group size of heterospecifics were informative, but less important, variables. There was no difference in peak visitation time for any species between sites of high versus low horse or cattle use. Despite temporal overlap, we did not find evidence of interference competition between feral horses, cattle, and pronghorn. We recommend future examination of interference competition and its biological consequences between introduced and native ungulates at water sources of varying size across sites, equid population levels, and livestock stocking rates.

Contrasting management paradigms for pronghorn in the arid Southwest and their northern range: a review

“…Free water locations also serve as sites of competition, particularly from cattle and horses (Gooch et al 2017, Hall et al 2018, Hennig et al 2021, Mattson and Holton 2022), which can increase during drier parts of the year and in areas with fewer water resources. Wildlife‐friendly fencing appeared to reduce visitation by mule deer ( Odocoileus hemionus ) but not pronghorn (Larsen et al 2011), so the strategic use of fences around water sources could reduce interspecific competition.…”

Habitat selection and space use overlap between feral horses, pronghorn, and greater sage‐grouse in cold arid steppe

“…Both species also exhibited selection for proximity to water. Horses and pronghorn have similar timing of watering activity (Hennig et al 2021 b ), which could lead to interference competition at watering sites (Gooch et al 2017, Hall et al 2018), but interference competition between the species may be less of a factor because of the high availability of water in this landscape (Hennig et al 2021 b ).…”

“…We created rasters of Euclidean distances to water sources and oil and gas well pads for each 30‐m pixel in our study area. Water sources included excavated reservoirs holding precipitation and runoff, groundwater, stream, or spring‐fed reservoirs, and naturally occurring springs (Hennig et al 2021 b ). We digitized all water reservoirs from 2017 National Agriculture Imagery Program 1‐m aerial imagery (U.S. Department of Agriculture Farm Service Agency 2017) and added known locations of springs provided by the Rawlins BLM Field Office.…”

Effects of grazer density, season and land cover on bird guilds in a restored conservation area

“…The data were downloaded through satellite processing from the interface of the GPS collar provider (Followit, Lindesberg, Sweden), thus no contact to the animals was needed to access the data. GPS collars comply with animal welfare requirements for horses (Collins et al 2014;Hennig et al 2018) and have been widely used also on cattle since decades, without causing harm or disturbance (Turner et al 2000;Ungar et al 2005).…”