It might sound crazy, but it’s absolutely true and some intrepid insects even target the tears of more dangerous animals
On the hunt for salt
Salt is scarce in the Amazon rainforest, but butterflies and bees have found an incredible method of ingesting valuable sodium. Flying insects visit the eyes of Amazon river turtles for a dose of salt. They flutter around the reptile’s face and dive in for a quick sip from the eyeball.
Turtles in the Amazon have a diet high in meat. This gives them more than enough sodium to keep their bodies functioning normally. Butterflies, on the other hand, have limited sources of salt. They target animal urine and sweaty humans to get their fill of minerals, but turtle tears are a much less risky source.
The bravest butterflies approach bigger animals for a salty drink. Caiman are members of the alligator family and in the Amazon they can reach lengths of five metres (16 feet). It takes a lot of guts to approach a resting caiman and dive in for a gulp of its tears.
Why salt matters
Salt is an essential to life as it can’t be produced in the body. It keeps the body’s chemicals in balance, regulates the nervous system and plays a major role in kidney function. In insects, salt maintains water levels in the cells. Water travels through cell membranes through a process called osmosis, and it moves to dilute high concentrations of dissolved ions like salt. If there is no salt in the cells, water will travel out to attempt to dilute the contents of the plasma. Long story short, without salt the insect would die so it’s vital to find a steady source of salt.
Does it hurt?
It’s still a mystery whether the turtles are bothered by their visitors. The butterflies place their proboscis on the eye’s surface very briefly and only take a minuscule amount. It might bother them, but it probably doesn’t hurt. It might make turtles more conspicuous to predators as the fluttering wings might catch the eye of a big cat or a caiman. It is highly likely that it blocks the turtle’s field of vision, making it more difficult to look out for danger.
Scientists are currently in the process of swabbing turtle eyeballs to find out if salt is all the butterflies are gaining from this behaviour. It’s possible that turtle tears contain something that provides additional benefits to buzzing insects that we don’t yet know about.
There are reports of other salt-hungry insects inflicting damage on unsuspecting animals. Fruit-feeding moths have developed a taste for blood, another excellent source of salt. The moths use their barbed mouthparts to pierce human flesh rather than fruit skin and can feed for stretches of 20 solid minutes. Only male moths have been documented performing this behaviour, so scientists suspect that they offer salt to female moths during copulation. How romantic.
See it yourself
Watch the footage below of bees drinking from turtle eyes in the Amazon rainforest.