Butterflies delicately kiss away the tears of their little turtle friends.

Well, that is the fairy-tale version of events, anyway. The more probable explanation is an insect in search of nutrients: in this case, sodium.

These butterflies are in the middle of an extreme salt craving.

Researcher Aaron Pomerantz took this Earth Capture shot during an expedition to Tambopata in the Peruvian rainforest.

To understand why the butterflies are salt-mad, Pomerantz says you need to understand Peru's unique geography.

"What happens in southeastern Peru - it's really fascinating," says Pomerantz.

Away from the coast, the Andes cut off weather and mineral deposits from rain that would come in from the Pacific Ocean.

"It's still the jungle, it still gets a lot of rain, but most of that is coming from the Atlantic side," he says. "By then it has travelled all the way across Brazil, all the way across South America, so you get a lot of rain, but it's depleted of nutrients."

Of all minerals, the main nutrient this rain is lacking is sodium.

It is not just butterflies on the hunt for a salty fix: all the region's plant-eaters are after a hit.

Animals need salt to regulate their bodies, and as herbivores have naturally lower levels of sodium in their diets, they have to seek out alternative sources.

"All these weird animal behaviours arise because of it," Pomerantz says.

For example, it is common to see parrots feeding on riverside clay lick, and to come across insects attracted to the sweat on your skin and clothing in the search for sodium.

"If you pee in a certain spot you'll probably attract a lot of insects after it," says Pomerantz.

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