The Journal of Wildlife Management 83(7):1607–1616; 2019; DOI: 10.1002/jwmg.21736NoteCache Pilfering in a Granivore Guild:Implications for Reintroduction ManagementRACHEL Y. CHOCK , 1,2 Department of Ecology & Evolutionary Biology, University of California Los Angeles, 612 Charles E. Young Drive E,Los Angeles, CA 90095, USAGREGORY F. GRETHER, Department of Ecology & Evolutionary Biology, University of California Los Angeles, 612 Charles E. Young Drive E,Los Angeles, CA 90095, USADEBRA M. SHIER, 3 Recovery Ecology, San Diego Zoo Institute for Conservation Research, 15600 San Pasqual Valley Road, Escondido, CA 92027, USAABSTRACT Reintroduction programs that release endangered species back into areas from which theyhave been extirpated rarely take competitive interactions between species into account. The endangeredPacif i c pocket mouse (Perognathus longimembris pacif i cus) is being reintroduced to parts of its former rangewhere multiple species of native rodents have overlapping diets. The granivorous species in this foragingguild compete for seeds exploitatively and through direct interference interactions, and pocket mice are thesmallest and least dominant species in the guild. Repeated aggressive interactions from resident hetero-specif i cs could lower the chances of reintroduced pocket mice establishing burrows during the post‐releasesettlement period. As such, temporarily reducing the density of competing species through exclusionaryfencing might be an advisable reintroduction strategy, in combination with other interventions, such aspredator exclusion. The presence of other members of the seed‐foraging guild, however, could have a netbenef i t for pocket mice, if the pocket mice pilfer from the other species’ seed caches more than the otherspecies pilfer from their caches. To test the frequency of cache pilfering between species, we conducted af i eld experiment with f l uorescent dyed seeds. Two of 10 pocket mice pilfered from heterospecif i cs, but only1 of 33 heterospecif i cs pilfered from pocket mice. In a f i eld‐enclosure experiment, we could not concludethat any of the 4 species tested used heterospecif i c scent to f i nd (or avoid) seed caches, and pocket micewere less ef f i cient in pilfering from artif i cial caches, recovering fewer seeds than the larger species. We didnot f i nd strong evidence that Pacif i c pocket mice benef i t from living in sympatry with larger, dominantspecies. Although further research is needed to elucidate the relationship between heterospecif i c density andthe prevalence of cache pilfering, a conservative reintroduction approach would be to select receiver siteswith low densities of known competitors to benef i t pocket mice during the critical post‐release estab-lishment phase. © 2019 The Wildlife Society.KEY WORDS cache pilfering, interspecif i c competition, Perognathus longimembris, pocket mouse, reintroductionbiology.Reintroductions and translocations, the human‐mediatedmovement of captive‐born or wild animals to areas fromwhich they have been extirpated, are considered importantconservation tools, but historically, they have low successrates (Armstrong and Seddon 2008). The highest rates ofmortality occur in the post‐release settlement period, thef i rst days to weeks following relocation (Stamps andSwaisgood 2007), with success often measured by indi-vidual survival and reproduction in the months to yearsfollowing reintroduction (Grif f i th et al. 1989, Fischer andLindenmayer 2000, Brichieri‐Colombi and Moehrenschl-ager 2016). Factors that inf l uence both the immediate andlong‐term success of reintroduced individuals should beconsidered to improve reintroduction success (Seddonet al. 2007, Armstrong and Seddon 2008). Reducingpredation pressure can improve survival rates of trans-located animals (Short et al. 1992), but interactions withcompetitor species have rarely been considered, despiteevidence that interspecif i c competition is an important partof community dynamics (Connell 1983, Moehrenschlageret al. 2013). Interspecif i c aggression is widespread (Ordand Stamps 2009, Peiman and Robinson 2010) and canreduce f i tness for subordinate species through its ef f ects onresource acquisition, reproduction, and survival (Lahtiet al. 2001). In some cases, interactions between residentsand reintroduced individuals have been documented tofavor residents (Burns 2005).Received: 30 November 2018; Accepted: 3 June 20191 E‐mail: rchock@sandiegozoo.org2 Current af f i liation: Recovery Ecology, San Diego Zoo Institute forConservation Research, 15600 San Pasqual Valley Road, Escondido,CA 92027, USA3 Additional af f i liation: Department of Ecology & EvolutionaryBiology, University of California Los Angeles, 612 Charles E. YoungDrive E, Los Angeles, CA 90095, USAChock et al. • Cache Pilfering in a Granivore Guild 1607
