Habitat use and social mixing between groups of resident and augmented bighorn sheep

Abstract

Monitoring dispersal, habitat use, and social mixing of released ungulates is crucial for successful translocation and species conservation. We monitored 127 female bighorn sheep (Ovis canadensis) released in three populations from 2000 to 2009 to investigate if augmented bighorns expanded and shifted seasonal ranges, used different habitat compared with resident females, and if animals mixed socially. Augmented bighorns in all populations expanded range use compared with residents by shifting utilization distributions. Size of utilization distributions, however, were smaller for augmented females compared with residents in all areas except one. Overlap of seasonal utilization distributions between augmented and resident bighorns and use of slope and elevation differed across populations. In two populations, differences in size and overlap of seasonal utilization distributions and use of slope and elevation supported the hypothesis that habitat use of bighorns in their source area influenced their habitat use after release. Mixing between resident and augmented adult females occurred on average during only 21% of sightings and was similar across populations. Our results clarify how augmented bighorns mix with resident animals and how habitat use is modified following augmentations. Such information is needed to improve bighorn sheep augmentations and can be applied to augmentations of other ungulates.

Evaluating wildlife translocations using genomics: A bighorn sheep case study

“…In addition, because bighorn sheep are a polygynous species, a small number of dominant rams may competitively exclude translocated males due to female mate preference for residents or poor condition after transport/release, suggesting that translocating a greater proportion of females may be more effective for augmentation (Mulder et al., 2017; Sigg et al., 2005). After an augmentation of females, translocated ewe groups may socially segregate from the resident population following release, which was observed in Taylor Hilgard after augmentation from Lost Creek in 1989 (Robinson et al., 2019; Roy & Irby, 1994). However, observed mixing of rams and ewes with different origins during breeding season or social mixing in later years resulted in hybrids descended from native and translocated animals after 24 years or about four generations (Figures 4 and ; Roy & Irby, 1994).…”

“…In addition, because bighorn sheep are a polygynous species, a small number of dominant rams may competitively exclude translocated males due to female mate preference for residents or poor condition after transport/release, suggesting that translocating a greater proportion of females may be more effective for augmentation (Mulder et al, 2017;Sigg et al, 2005). After an augmentation of females, translocated ewe groups may socially segregate from the resident population following release, which was observed in Taylor Hilgard after augmentation from Lost Creek in 1989 (Robinson et al, 2019;Roy & Irby, 1994 Augmentations are often promoted for genetic rescue (Hogg et al, 2006;Tallmon et al, 2004;Whiteley et al, 2015). To increase effectiveness of a genetic rescue, source and recipient populations should have been previously connected but recently isolated to allow differentiation over multiple generations in the past 500 generations (Allendorf & Luikart, 2009;Falconer et al, 1996;Frankham et al, 2017).…”

“…Hilgardafter augmentation from Lost Creek in 1989(Robinson et al, 2019;Roy & Irby, 1994). However, observed mixing of rams and ewes with different origins during breeding season or social mixing in later years resulted in hybrids descended from native and translocated animals after 24 years or about four generations(Figures 4 and S1;Roy & Irby, 1994).…”

Comparison of Effects of Shed Antler Hunting and Helicopter Surveys on Ungulate Movements and Space Use

“…For example, female bighorn encountering excessive numbers of hikers during lambing failed to return to historical high‐valued lambing areas (Papouchis et al 2001, Wiedmann and Bleich 2014). Such behavior by females can be detrimental as bighorn lambing areas are increasingly being recognized as important habitat features for population growth (Smith et al 2015, Karsch et al 2016, Robinson et al 2019).…”

Determining Timing of Births and Habitat Selection to Identify Lambing Period Habitat for Bighorn Sheep

“…In similar, adjacent habitat these methods could be applied to conserve and manage habitat for these ungulates and to identify lambing period habitat for reintroduction and translocation sites. Reintroduction and translocation continue to be useful management tools for bighorn conservation (Wiedmann and Sargeant, 2014;Boyce and Krausman, 2018;Robinson et al, 2019). In Utah >1,000 Rocky Mountain bighorn sheep and >850 desert bighorn sheep have been released in areas of historical habitat since 1966 (Olson et al, 2008;Shannon et al, 2008; Utah Division of Wildlife Resources [UDWR], 2018).…”