A Comparison of the Ecology of Resident and Translocated Beavers Used for Passive Restoration in Degraded Desert Rivers

Ecosystem engineers are species that create, destroy, modify, or maintain habitat. As ecosystem engineers, beavers have the potential to assist in stream restoration. Translocation is the capture and relocation of an animal to another area. Translocation of nuisance beavers has become a popular method to reduce human-wildlife conflict and restore waterways. However, few projects monitor beavers after release and compare behavior to naturally occurring resident beavers. Translocations to desert rivers are also rare. We captured, tagged, and monitored 47 beavers which we translocated to desert river restoration sites on the Price and San Rafael Rivers, Utah, USA. We compared translocated beaver behavior and activity to 24 resident beavers we also captured and tagged for monitoring. We found high survival rates for resident adult beavers and lower survival rates for resident subadult, translocated adult, and translocated subadult beavers. There were many more river reaches with dams after beaver translocations than before translocations, although we were unable to determine which beavers were responsible for dam building. In general, resident subadult and translocated adult and subadult beavers used ten times longer stretches of river than resident adult beavers. Translocated and resident subadult beavers moved farther from release sites and faster than resident adult beavers in the first six months after release. In contrast, all beavers had similar short-term activity levels, indicating day-to-day activities such as searching for food and resting may not be changed by translocation. Our findings suggest translocated beavers exhibited survival rates, dam building behavior, and movement patterns most similar to resident subadult beavers during dispersal, which is the movement away from the location where a beaver was born. Many translocated beavers left the study sites in search of a suitable area in which to settle, but even those beavers that left the restoration areas may still be benefiting other degraded stretches of river. Further, translocations led to additional beaver dams in the restoration sites, the common goal of beaver-assisted restoration. Low probability of staying near release sites, a high death rate, and wide-ranging movement patterns should be anticipated when translocating beavers. Multiple beaver releases at targeted restoration sites may eventually result in some settlement and dam-building. Resident beavers did not appear to be negatively affected by translocated beavers introduced into the rivers, indicating that translocations can be used to increase low beaver populations to potentially help reach restoration goals more quickly. Improving methods of restoring healthy ecosystems, such as beaver-assisted restoration, is important to maintaining diverse, abundant life globally