By the time he was 20, entomologist Phil Torres had already discovered 40 new insect species on research expeditions in Venezuela and Mongolia. Since then he's spent two years doing conservation science in the Amazon jungle and his jobs doing research and hosting science programs take him to all corners of planet Earth. So to say he's seen more than most of us is an understatement.

But while he was traveling down the Tambopata River in Peru, he saw something pretty rare — but also only something not everyone would recognize as special, something he said was ""one of the most bizarre, strange, beautiful, fascinating things I have ever seen in my entire life," in the YouTube video below.

Thinking quickly, he was able to capture it on film, to share with the world, via his YouTube channel, The Jungle Diaries. It was the rare sight of butterflies drinking turtle tears. He counted about eight different species of butterfly, which were so distracting to the turtles that they didn't even dive in the water as Torres' boat came close, allowing the incredible footage below.

What were the butterflies doing? They were after sodium, which they can't find in their typical food sources but need for reproduction, among other things. This species of turtle can't pull its head into its neck (not all turtles can), so they have to endure the thirsty insects flitting around their heads. This is an example of commensalism — where two species interact and one benefits; the other is unhurt, but doesn't benefit in any way.

I had to know more about this amazing sight Torres was lucky enough to see, and he agreed to answer my questions. (And you know I'll be keeping my own eyes peeled next time I'm floating down a river in South America to see something like this!)

MNN: Since the butterflies need salt and otherwise can't find it in their environment, are they attracted to anything salty?

Phil Torres: Yes, they go after pretty much anything salty. I’ve seen them imbibing on sweaty rudder handles of boats, backpacks laid on the ground after a long hike, dirty field clothes drying on a laundry line, even my shoulder or neck sweat from time to time. It is pretty common for scientists to bait tropical butterflies with a mix of fermented fish and urine, this rotting combination of a resource high in amino acids and salts smells terrible to humans but is irresistible to some groups of butterflies. In almost every case, it is the male butterflies that participate in this salt- and tear-drinking behavior, as they use the sodium as a nuptial gift during mating to help the female’s reproductive success.

How are the butterflies able to find salt in their environments? Do they sniff it out?

They use a mix of olfactory cues and visual cues to find the salt. They have very sensitive antennae that can help them smell out a good salty resource, and will use other detectors once they land to test if the resource is as good as it smells, like sensors on their feet (tarsi). They also use visual cues and know that if they see a single or multiple brightly colored butterflies in the mud (or on a turtle) that is probably a good place to go to get some sodium. You can take advantage of this by placing bright, neon-colored pieces of plastic on the shore of a river and it will attract curious male butterflies wondering if this could be a place to grab a salty drink.

Phil Torres holding a camera with a large zoom lens while sitting in the rear of a canoe. Phil Torres on the (photo) hunt with his camera. (Photo: Phil Torres)

Have you ever seen this before? Was it hard to get the footage?

I have seen it up close with bees drinking from turtle eyes, and only briefly before with the butterflies — and not nearly as many. The turtles generally are pretty shy and will dive into the water once a boat comes near, which is what happened in the past when I’ve seen glimpses of this behavior. In this case, I think the turtles were so distracted by all of the butterflies on their face that they couldn’t be bothered with us. There are other photos I have seen of this behavior with turtles and caiman basking in the sun with a dozen or so butterflies on them, and it was always a dream of mine to document it, and finally I was in the right place at the right time with a camera ready.

Might anyone see this between any two types of butterfly and turtle? Or is this the only place that this particular brand of commensalism takes place?

This is a regional behavior that I have seen photos of throughout most of the Amazon, in some regions like Ecuador it tends to be more caiman tears, and in Peru it tends to be more turtles. The butterflies are happy to take advantage of any animal basking in the sun that can't easily swat them away. While it is known to happen it is really rare to see, I have taken dozens and dozens of boat rides in the Amazon and I've seen hundreds of basking turtles on the side of rivers, and this was the best example of butterflies feeding on turtle tears I've come across. I hope to see it again some day, but it may take a few dozen river trips more.

Starre Vartan ( @ecochickie ) covers conscious consumption, health and science as she travels the world exploring new cultures and ideas.