Moths drink the tears of sleeping birds

00:01 20 December 2006
NewScientist.com news service
Debora MacKenzie

A close-up of the moth’s proboscis reveals its barbed tip (Image: Roland Hilgartner / Mamisolo Raoilison)
A species of moth drinks tears from the eyes of sleeping birds using a fearsome proboscis shaped like a harpoon, scientists have revealed. The new discovery – spied in Madagascar – is the first time moths have been seen feeding on the tears of birds.

Roland Hilgartner at the German Primate Centre in Göttingen, Germany, and Mamisolo Raoilison Hilgartner at the University of Antananarivo in Madagascar, witnessed the apparently unique sight in the island state’s Kirindy forest.

Tear-feeding moths and butterflies are known to exist elsewhere in Africa, Asia and South America, but they mainly feed on large, placid animals, such as deer, antelope or crocodiles, which cannot readily brush them away. But there are no such large animals on Madagascar. The main mammals – lemurs and mongoose – have paws capable of shooing the moths. Birds can fly away.

But not when they are sleeping. The Madagascan moths were observed on the necks of sleeping magpie robins and Newtonia birds, with the tip of their proboscises inserted under the bird’s eyelid, drinking avidly (scroll down for images). This was during the wet season, so the scientists think the insects wanted salt, as the local soils are low in sodium.

But sleeping birds have two eyelids, both closed. So instead of the soft, straw-like mouthparts found on tear-drinking moths elsewhere, the Madagascan moth has a proboscis with hooks and barbs “shaped like an ancient harpoon”, Hilgartner says.

This can be inserted under the bird’s eyelids, where the barbs anchor it, apparently without disturbing the bird. The team does not yet know whether the insect spits out an anaesthetic to dull the irritation. They also want to investigate whether, like their counterparts elsewhere, the Madagascan tear-drinkers are all males who get most of their nutrition from the tears.