For a scientist who studies snakes, getting to watch a turf battle between two snake rivals makes for a very good day. The behaviour is only rarely seen, so wildlife ecologist Dr Dave Steen was naturally excited to receive footage of two duelling vipers recently. And those excitement levels went up a notch when he realised the snakes were two different species...

The fight scene was caught on camera in Snowball, Arkansas by citizen scientist Dawn Kelly, who is now working with Steen on a scientific manuscript describing the event. As for the twisting combatants, you're looking at Agkistrodon piscivorus (which goes by many common names, including cottonmouth) and Agkistrodon contortrix, known as the copperhead. Both animals belong to the pit viper family.

"Combat among vipers is something I've always wanted to see for myself in the field; it's kind of like the holy grail of snake behaviours for folks that appreciate snakes in their wild environment," says Steen.

Many snakes engage in these kinds of wrestling matches to compete for females come breeding season, but the fact that Kelly's video shows interspecific combat – that's combat involving different species – adds another level of interest here. In fact, this could be the first evidence of such behaviour ever recorded among vipers, according to Steen. "Not only is it neat to see but it raises all kinds of interesting questions regarding what is going on between these two animals," he adds. "I'm curious to know what species of snake they're competing over. Maybe there's a female of each out there hiding in the grass. We just don't know."

Such snake battles are so rarely seen, in fact, that those lucky enough to witness them sometimes mistake the behaviour for mating. When two black mambas were filmed in a battle for dominance in South Africa's Kruger National Park last year, the video sparked lots of debate on social media.

Like the vipers in Kelly's video, these mambas were rival males competing over a female. In many snake species, females take a hiatus once they're pregnant, and are unable to reproduce again for some time – so a mate who's ready and willing to breed is a prize worth fighting over.  

"Sometimes females may respond to courtship in a way that looks like combat, but the large size of these snakes (indicative of males) and the prolonged wrestling match suggests we are indeed looking at male combat," says Steen of the viper clip. 

The fight doesn't look particularly ferocious, and that's because it's more about bravado than intent to kill. In the wild, a battle that carries a high risk of serious injury or death is generally one to avoid, and this form of "ritualised" combat is more about showing the opponent your strength and stamina. 

But perhaps the most exciting thing about this rare clip is that it shows citizen science in action. Without wildlife lovers like Kelly sharing their interesting finds with the experts, scientists would miss out on a wealth of important knowledge. There's still a lot we have to learn about the courtship rituals of many snake species, including cottonmouths, and this clip is just one small piece of the larger puzzle. 

"There are only so many traditional scientists to go around. By empowering citizen scientists we can get so many more people out there looking at nature, thinking about what they are seeing, and collaborating with each other so we can better understand the natural world around us," says Steen.


Top header image: Stephen Durrenberger, Flickr