We compared patterns of growth in juvenile yellow-bellied marmots (Marmota jlaviventris) between 2 years in which precipitation differed, and we determined if mass at entry into hibernation affects over-winter survival. Juveniles exhibited an asymptotic growth pattern with mass gain for a mean of 60.8 days, followed by stable mass until entry into hibernation. Growth ceased in early September, shortly after the end of the plant growing season. Juveniles born in 1991, a year of late snowmelt and low summer precipitation, entered into hibernation at significantly lower mass than juveniles born in 1992. Juveniles born in 1992 survived better despite experiencing a long winter during which they spent more days in hibernation and lost more mass. Overall, heavier juveniles were more likely to survive hibernation. Further, mass at entry into hibernation apparently had a greater effect on over-winter survival than did winter severity.

We experimentally address the theoretical potential for managing ecosystem engineer species to support suites of species in degraded habitats. Historically, the ecosystem engineer California ground squirrel Otospermophilus beecheyi supported a grassland food web through widespread burrowing activity. Currently, ground squirrels are not a threatened species, but like many other ecosystem engineers, they exist at densities too low to fulfill their engineering role in many locations. Our objective was to implement short‐term treatments, including squirrel translocation, to re‐establish key ecological processes on protected reserve lands. We manipulated vegetation and squirrels in a replicated, large‐scale field experiment for 2 years, and monitored through a third year. Vegetation mowing and soil decompaction treatments reduced grass density and thatch depth. Squirrel translocation accelerated squirrel settlement and activity in target sites. Of the more than 1000 burrow entrances remaining through the third year, nearly all burrows were concentrated in the plots that received squirrel translocation. We found significant additive effects of squirrel translocation and vegetation management on the spatial footprint of squirrel activity. Noteworthy and persistent engineering effects were achieved through squirrel activity, and both vegetation management and squirrel re‐establishment were needed to stimulate squirrel activity. The overarching goal of this experiment was to provide conservation managers with a cost‐effective tool for restoring degraded habitats to a hybrid ecosystem state with improved suitability for species of conservation concern, in this case, the western burrowing owl Athene cunicularia hypugaea.

Translocation of abundant but declining ecologically important species for re‐establishing more sustainable ecosystem function is a neglected but promising form of conservation intervention. Here, we developed a translocation program in which we capture pests and release ecosystem engineers, by relocating California ground squirrels Otospermophilus beecheyi from areas where they are unwanted to conserved lands where they can perform ecosystem services such as burrowing and vegetation alteration. We accomplished this using an experimental approach in which some factors were measured or experimentally manipulated, while others were held constant. We translocated 707 squirrels and examined survival and movement patterns as a function of several translocation tactics and ecological factors. We released squirrels at 9 different plots with varying ecological contexts and at each plot experimentally manipulated post‐release habitat using mowing, mowing plus the use of augers to establish starter burrows, and controls that remained unmanipulated. The most influential variables affecting short‐term survival, dispersal, and long‐term persistence were factors relating to soils and vegetation structure. Translocated squirrels had higher initial survival on plots where dense exotic grasses were experimentally altered, greater dispersal when released at sites with less friable clay soils, and improved long‐term persistence at sites characterized by more friable soils associated with metavolcanic than alluvial geological layers. Squirrel persistence was also improved when translocations supplemented previous translocation sites than during initial translocations to sites containing no resident squirrels. Our results demonstrate how California ground squirrels can be successfully translocated as part of a larger objective to favorably alter ecological function in novel grassland ecosystems dominated by non‐native vegetation. In broader context, our study highlights the importance of testing release strategies, and examining habitat variables and restoration techniques more closely when selecting release sites to improve translocation outcomes.

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