Research results unexpected
Desert bighorn sheep have been translocated into the Trans-Pecos region of Texas for decades. What methods of relocation works the best was studied by the Borderlands Research Institute in a study entitled, Social Interaction and Survival of Translocated Desert Bighorn Sheep.
What researchers learned was quite surprising.
Over the decades, two types of releasing translocated animals have been used. The hard release is the immediate release into the recipient habitat. Soft release involves holding individual animals in a large enclosure within the recipient habitat for several weeks, with the hope the semi-protected state would allow the animals to learn about their new habitat in relative security prior to release, leading to higher survival.
At the Black Gap Wildlife Management Area, 30 resident and 70 translocated desert bighorns were GPS collared.
Of the 70, 28 were hard released into the recipient habitat and 42 were soft released into a 500-acre enclosure for three weeks before release.
Researchers looked at social integration, habitat use and configuration and survival.
As expected, the resident animals had the greatest 2-year survival. However, sheep hard-released into the habitat fared better than soft-released sheep.
Researchers concluded the soft-released sheep were less likely to integrate with resident sheep, while hard-released animals were more likely to integrated into resident social groups and use similar habitat. “While many argue soft-release methods permit animals to acclimate to their new environment, our results indicate they actually hindered acclimation by preventing social integration with resident individuals and learning from them,” BRI said in a description of the research. “Translocated desert bighorn sheep were more likely to integrate with resident herds and survive when hard released.”
BRI advised avoiding soft release methods when resident sheep are present, favoring hard-release methods.
Photo subject to copyright David J. Sams