The follow up to the last post --- why study gap crossing --- is why study gap crossing in Australia.
The first project I did for my PhD was to look at how paradise tree snakes cross gaps. These snakes are one of 5 species in the genus Chrysopelea, which is the only genus of snakes that can glide. My advisor, Jake Socha, has been studying various aspects of their gliding since he was in grad school, leading him to record awesome videos like this:
As cool as the gliding is in that video, the part I focused in on was the launch. As you might imagine, the ability to jump is somewhat unusual in legless snakes. There are some snakes who can strike so forcefully that it carries them off the ground, but no one had studied jumping in tree snakes, or looked at how snakes might use jumping as a way of moving around.
Jake and another researcher with an interest in snake biomechanics, Bruce Jayne, had theorized that perhaps the jumping behavior used by the flying snakes to launch glides could also be used to enhance their gap-crossing ability. Most snakes use a cantilever to cross gaps, which is where they extend outward in a relatively straight line from one branch to the next. They can extend a really impressive distance this way, but the behavior is fairly limited compared to jumping. After documenting gap-crossing behaviors in flying snakes in the lab at Virginia Tech, I confirmed that flying snakes do use jumping to cross gaps, and it enables them to cross gaps much larger than other snakes can cross (relative to body size).
What does this have to do with Australian tree snakes? Well, the common tree snake and the northern tree snake in Australia are in the genus Dendrelaphis, sometimes called the bronzeback snakes. These genus is the most closely related to the flying snakes, but as far as we know none of the bronzeback snakes can glide. Jake had previously filmed an Indonesian bronzeback doing a jump between two branches, but no one had documented the behavior in detail. We don't know whether the jumps are the same in the two groups (the Australian tree snakes and the flying snakes), or how having the ability to jump but not glide influences gap-crossing behavior and performance.
Since it’s fairly difficult to bring these snakes to the lab, I went to the snakes. The common tree snake is fairly widespread through the eastern coast of Australia, but the northern tree snake is really only around in Far North Queensland. James Cook University runs a research station in the Daintree Rainforest, so I travelled there from November to the January to try to catch some snakes and film them crossing gaps of different sizes. I’ve just left that field station, and am now based at the Sunshine Coast, where I’m hoping to collect data from a few more of the common tree snakes. I had an amazing time in the Daintree, and over the next few weeks, I’ll be posting some photos and stories from the trip. Please feel free to comment with any questions and I’ll do my best to answer them!
My project is supported by a National Geographic Early Career Grant, the Company of Biologists Travelling Fellowship, and the Virginia Tech Graduate Student Association's Graduate Research Development Program.