By Kyle Melnick
William Hayes was conducting research into snake venom a few years ago when he met up with some colleagues in the mountains of Southern California.
They handed over two rattlesnakes, which he corralled into a bucket and put in the back seat of his car. As the college professor drove back toward his lab, he noticed the snakes sounded oddly quiet.
It seemed like they were rattling less than usual.
In the following months, Hayes and a team of researchers started to study whether rattlesnakes were less stressed when they were near other snakes - leading to softer rattling.
Researchers placed snakes into buckets, first alone and then with a companion. Then they gently hit the buckets with pipes to monitor the reptiles' reactions.
Researchers found that snakes, like humans, are calmer when they have company, according to the results published in the Frontiers in Ethology journal.
"These animals aren't all that different from us," Hayes, a biology professor at California's Loma Linda University, told The Washington Post.
"They're sentient creatures. They have emotions; they have fear; they experience pain."
In 2019, Hayes had originally picked up the rattlesnakes from colleagues in the San Jacinto Mountains to test their venom.
Hayes said that at first, he thought he had imagined the snakes' quieter rattles on the drive back, so he and other researchers looked up a possible cause.
While rattlesnakes are known to vibrate their tails to scare predators, researchers couldn't find studies about how companionship influences rattlesnake behaviour.
"In the past, people often viewed snakes and reptiles as not being very complex and not being able to make decisions or have feelings," said Chelsea Martin, a Loma Linda University PhD student in biology.
Researchers reviewed the effects companionship has on other animals - including birds, pigs and horses - to help guide their experiment.
In 2020, they gathered 25 Southern Pacific rattlesnakes, which were donated by nearby snake removal companies.
In their Loma Linda lab, researchers placed the snakes in five-gallon plastic buckets and attached heart monitors to their bodies.
They then tested snakes in three conditions: alone, with another snake and with a rope the size of a snake.
To simulate a stressor, researchers banged on the buckets using two pipes. They recorded the snakes' heart rates and how long they rattled.
The team found that the snakes were most frightened when alone.
And they were most calm when there was another snake in their bucket.
In some cases, snakes barely produced any sound when two were together. The findings were true for both male and female snakes.
After their research, Hayes released the snakes back into the mountains. Martin plans to further study the long-term effect companionship has on snakes and other reptiles. She and Hayes also hope their research creates more empathy for rattlesnakes.
"People often think of snakes as being just these otherworldly creatures and think they're really different," Martin said. "But I mean, we do have a lot of similarities."