The fruits of confusion

USING a decoy to confuse the enemy is a splendidly effective way to save your skin. Scientists have recently discovered that an Australian shrub called Hakea trifurcata produces leaves that impeccably imitate its fruit to confuse the white-tailed black cockatoo, a voracious consumer of its fruit (Nature, Vol 368, No 6468).

Some plants deck themselves up gaudily to seduce animals into eating their fruit and thus dispersing their seeds. But other plants like the Hakea run the risk of birds eating too many of their seeds. Saving its seeds is important for the Hakea, because unlike its Australian cousins, it is unable to re-sprout after the frequent fires that run through Australian scrubland and is solely dependent on its seeds for survival.

Australian scientists P K Groom, B B Lamont and H C Duff say that whereas the juvenile Hakea produces only narrow, needle-like leaves, it develops as it matures broad yellow-green leaves that impersonate the fruits which house the seeds.

These broad leaves are more densely arranged near the fruit than on other parts of the plant and take the cockatoos' attention away from the real fruit, the scientists say. They tested their hypothesis by offering cockatoos fruit-laden branches with and without imposter leaves; they found the number of fruits eaten by the birds was significantly higher in the latter case.