Can Acorn Tannin Predict Scrub-Jay Caching Behavior?
- Cite this article as:
- Fleck, D.C. & Woolfenden, G.E. J Chem Ecol (1997) 23: 793. doi:10.1023/B:JOEC.0000006411.68081.14
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We tested the hypothesis that animals caching acorns for future food use may preferentially cache acorns high in tannin content. We used a population of Florida scrub-jays (Aphelocoma coerulescens) that cache acorns from four oak species. Tannin activity in acorns was measured by protein precipitating ability (PPA). Logistic regression models accurately predicted frequency of acorn caching among the oak species, using frequency of usable acorns and PPA loss during burial as predictor variables. Among the four oak species, frequency of caching increased with both increasing frequency of undamaged acorns at peak harvest time, and increasing loss of PPA during burial. Other regression models accurately predicted frequency of undamaged acorns for each species, using green acorn PPA and buried acorn PPA as predictor variables. Among the four oak species, frequency of usable acorns tended to increase with increasing green acorn PPA, and decreased with buried acorn PPA. We suggest that a deterrent effect of tannins on insect larvae is responsible for the differences in frequency of acorns usable to jays among oak species, and that jays select acorns for burial by assessing insect damage. Species differences in PPA change during burial probably reinforce this pattern of scrub-jay caching behavior.