Robo-squirrel, the robotic squirrel in the hills of San Jose.
The Bay Area may be the high-tech capital of the nation, but increasingly, biologists working at some of the area’s universities are turning to technology, too. The game-changing field of “bio-robotics” is opening a new window onto animal behavior.
That can be seen in the hills high above San Jose, where there’s a timeless battle going on between predator and prey - California ground squirrels and Northern Pacific rattlesnakes.
Rulon Clark, a biologist at San Diego State University, is studying this unique interaction at the Blue Oak Ranch Reserve. As he shows me the field site, he warns me that the grassy hills are chock full of rattlesnakes. “Just try to watch where you’re stepping,” he says.
Clark and his team monitor these snakes with web cameras set up outside their underground burrows – sort of like rattlesnake reality TV. They also capture snakes and give them radio tags.
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Using the signal, Clark tracks a male snake named Vader (one of several Star Wars-named snakes) to a small patch of grass that looks rattlesnake-free -- until Clark points out a colored marker.
“See that little splash of pink? That’s his rattle segment,” he says. “He’s really hard to make out. This is a stereotypical ambush posture.”
The coiled rattlesnake is waiting for ground squirrels, which run all over these hills eating seeds and grass. “They’re like a loaded gun. They’re just ready to launch.”
Squirrels and Snakes Nose to Nose
Rattlesnakes have a powerful sense of smell and heat-sensitive vision. They strike and inject deadly venom in half a second flat. Against a predator like that, most animals would run away.
“Our tendency for snakes is to get out of there, right? But the squirrels, they’ll cautiously approach,” says Clark.
The squirrels stand their ground, inching closer to a coiled snake. They do a strange dance, waving their tails back and forth rapidly. “They’ll tail flag – that’s this anti-snake display that they give,” Clark says.
The squirrels also pump blood to their tails, increasing the temperature a few degrees. Amazingly, they only do this with rattlesnakes, which can detect the heat. Clark says these squirrel tricks seem to work – the snakes tend to give up.
“This tail-flagging has co-evolved with the snakes into a signal of sorts,” Clark says. But exactly what the signals are in this complex predator-prey dialogue is hard to study. So, Clark is enlisting a special agent, named “robo-squirrel.”
“Robo-squirrel is an actual ground squirrel that’s taxidermied so it’s hollow inside,” says Clark. Built by engineers at UC Davis, the robot has a mechanical tail that moves back and forth and heats up, just like a live squirrel.
Robo-squirrel moves towards a snake on a track and Clark cues different versions of the squirrel dance so he can study the snake’s response. Does it bite or back off? Clark says this kind of technology has changed the way biologists study animal communication.
But squirrels aren’t the only animals going high-tech...
Six-Legged Disappearing Act
“We think cockroaches are also disgusting, like most people do, but they have a lot of secrets,” says Robert Full, a biology professor at UC Berkeley. He studies how cockroaches get around so well and lately, he’s been trying to understand how these crafty critters seem to vanish as soon as you get close.
Full shows me a high-speed video of a cockroach running off a platform. “So they run really fast to the end of the ledge and hook their hind legs on like grappling hooks,” he says.
DASH, the robotic cockroach at UC Berkeley.
The cockroach grabs the edge, flips over, and holds on to the bottom of ledge upside-down. This happens faster than humans can react, so it looks like the cockroach disappears.
Full says this isn’t just a good escape trick. “We use a lot of the principles we discover to inspire the design of the next generation of robots.“ He called up his engineering colleague Ron Fearing and asked, “can we demonstrate the agility of small robots by trying to do a behavior like this?”
They enlisted DASH, a robotic cockroach. It’s about four inches long and is made of a paper exoskeleton. It runs about the same speed as a cockroach.
In another high-speed video, the robotic cockroach does the same trick, flipping around a ledge with the help of a Velcro pad. Full says this kind of agility could help them build robots for real world situations, like helping emergency responders.
“If you really want to make search and rescue robots that can go into rubble. Imagine something from an explosion or a tornado or an earthquake, then you’re going to need something far more maneuverable than we have now,” Full says. The robotic cockroaches also serve as physical models, teaching them about the mechanics of real roaches.
Full says technology and robotics are reshaping the field of biology. “Now you have the capability easily of high speed cameras, of remote monitoring, of just seeing thing at the organism level in the lab and in the field. Now, you have new hypotheses that you couldn’t possibly have before.”
