Predation risk in tree squirrels: implications of the presence of free-ranging dogs

Abstract

Small mammals show variations in activity patterns due to the use of resourcesand the risk of predation. However, in the case of tree squirrel species, the factorsthat affect their activity patterns are poorly studied. We used camera trapping toinvestigate the activity patterns of three different squirrel species of the genusSciu-rus, two species of squirrel (Sciurus aureogasterandS. oculatus) from Mexico andone from the Iberian Peninsula (S. vulgaris). In addition, we compared their activ-ity patterns with the potential predator community and their most important preda-tors (Mexico: gray foxUrocyon cinereoargenteus, ringtailBassariscus astutus,OpossumDidelphis virginiana; Spain: red foxVulpes vulpes, pine and stone martenMartes spp.), and with feral and free-ranging dogs (Canis lupus familiaris). Weevaluated the predation risk by the carnivore community on the squirrels when theydescend to the ground by studying their temporal overlap and observing if thesquirrels have different activity patterns adjusted to the carnivore community ineach study area. The results showed that the three species of squirrels consistentlydescended to the ground during the day, showing a variable maximum peak ofactivity between 8:00 and 12:00 h. Temporal overlap of activity patterns of thethree species with the carnivore community was low (D=0.12–0.36), same as withthe main predators (Mexico: gray foxD=0.14–0.21, ringtailD=0.08–0.09, opos-sumD=0.06–0.07; Spain: red foxD=0.39, martensD=0.22). However, tempo-ral overlap of activity patterns with the domestic dog was moderate-high in thethree squirrel species (MexicoD=0.55–0.88, SpainD=0.79). These results showthat the species of the genusSciurushave adjusted their activity patterns of grounduse to reduce predation risk by wild predators but not with feral and free-rangingdogs, something which can pose a serious conservation problem for these species.