Small mammals locate buried wet seeds more efficiently than buried dry seed
s. This may be attributable to emission of volatile compounds by the seeds.
To test this hypothesis I measured emission of volatile compounds from see
ds of three plant species (Pinus contorta, Purshia tridentata and Achnather
um hymenoides) under wet and dry conditions using solid phase micro-extract
ion, gas chromatography/mass spectrometry headspace analysis. Seeds respond
ed in two ways: (1) wet seeds released different, generally greater, amount
s of volatile gas than dry seeds and (2) wet seeds and dry seeds released d
ifferent compounds. Pinus contorta seeds release greater amounts of three c
ompounds when wet: Purshia tridentata seeds release two compounds when dry
that are not released when wet, and release increased amounts of two compou
nds when wet, and increased amounts of two compounds when dry; Achnatherum
hymenoides releases at least 22 compounds, one of which is released in larg
e concentrations when wet. These data suggested two mechanisms by which sma
ll mammals locate buried seeds. First, small mammals may be sensitive to re
lease of differing concentrations of volatile compounds by seeds. Second, s
mall mammals may be sensitive to compounds released by wet seeds that are n
ot released by dry seeds. Ability of seeds to survive depredation by graniv
ores may be an adaptive trait influenced by natural selection.