Behaviour runner-up: Ssstandoff by Dr Gregory Funston

When digging dinosaurs in southern Alberta, Canada, prairie rattlesnakes (Crotalus viridis) are ubiquitous neighbours. Returning to camp from an excavation of a horned dinosaur, we were treated to a show by two very large (1.5-metre-long) males, tussling for dominance. Intertwining their necks, they would raise up off the ground and attempt to slam their competitor down. After a few minutes of intense battle, they separated and moved off, apparently unharmed. Despite a perception as violent animals, seeing two snakes interact like this is very rare

Photograph: Gregory F Funston/Royal Society Publishing