Scatterhoarders use seedlings as cues of belowground food availability

Abstract

Animals benefit from scatterhoarding, storing food around their home range for use during a period of scarcity, by later eating the stored food. Seedlings may be used as cues of belowground food. We investigated whether scatterhoarders such as eastern gray squirrels ( Sciurus carolinensis Gmelin, 1788) and eastern chipmunks ( Tamias striatus (Linnaeus, 1758)) use characteristics of seedlings and their seeds as physical cues of the value of the seed. We buried 176 germinating seeds (white oak ( Quercus alba L.) and northern red oak ( Quercus rubra L.)) in a hardwood forest in Alabama, USA. Seeds were recovered faster with longer leaves (rate ratio (RR) = 0.68, 0.58–0.78, 95% confidence limits (C.L.)) and taller stems (RR = 0.91, 0.88–0.93, 95% C.L.) during spring 2022, and with a smaller number (RR = 1.15, 1.04–1.27, 95% C.L.) of longer leaves (RR = 0.81, 0.70–0.93, 95% C.L.) during fall 2022 (both P < 0.0001). For all seeds, we found that longer roots increased the likelihood of seeds being used (rather than ignored; odds ratio = 1.45, 1.00–2.09, 95% C.L., P = 0.05). We found new evidence suggesting that hoarders use aboveground cues from the seedling to dig it up and belowground seedling cues to assess seed value. These findings add to our understanding of assessing food availability for hoarding animals.