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Zoologger is our weekly column highlighting extraordinary animals – and occasionally other organisms – from around the world

Species: , sometimes
Habitat: dribbling on luckless plants in

We’ve all eaten something that doesn’t agree with us, but probably not on the scale that moose do. They eat a grass that is so toxic, it can make animals’ hooves fall off.

Yet the moose are resolutely hoofed, suggesting they have a way to counteract the toxin. That makes sense: evolution would favour moose that could handle more of the toxin. There are precedents: , and some plant-eating insects go even further and actually .

No-one thought that backboned animals could pull off the insects’ trick, but now it’s been discovered that moose can switch off a plant’s toxic defences at source. They do it using a mystery chemical in their saliva that interferes with the signalling processes inside the plant. In effect, moose can detoxify their food by licking it.

Loose moose

Moose are the largest species of in the world. Males are . During spring the males also grow the largest antlers of any living animal.

The males’ size and antlers have evolved because they compete so furiously for females. Males may defend a single female, or an entire harem, but either way they face regular challenges from rival males. If a female is being courted by a male she regards as too small, – attracting a larger male who is likely to challenge the original male.

The competition plays out in in which the two males lock antlers and . It’s not a fight to the death, more a test of strength, and often a small male will give in without a fight.

Growing these massive antlers, and then fighting over girls, takes a lot of energy. So moose need to eat a lot. But they have a problem: a significant part of their diet is a common grass called . These plants contain a fungus called , which makes a toxin called ergovaline. Grazing animals that eat too much ergovaline can .

Magic dribble

So how come moose can eat the stuff? of the University of Cambridge and his colleagues decided to find out.

Tanentzap’s team simulated grazing by clipping red fescue and smearing it with moose or saliva. Eight weeks later, the ergovaline levels in saliva-smeared plants were between 40 and 70 per cent lower than those in unclipped plants or in clipped plants smeared with water.

“Herbivores can actually fight back,” says Tanentzap. “No one has ever thought of this.” Many other grazing animals might have similar saliva tricks, he adds.

The moose saliva also slowed the growth of the fungus itself, but that is less surprising because many animals’ saliva has antifungal properties – including human saliva. The impressive bit is the effect on ergovaline production, which must involve interrupting a signal passed from the plant to its fungal inhabitants.

“If these animals continually graze the same plants, then it would be quite beneficial,” says of Penn State University in University Park, Pennsylvania. “We are still uncovering novel roles for saliva,” he says. For instance, .

Journal reference: Biology Letters, DOI: