Robosquirrel

Robosquirrel refers to several versions of robotic squirrels developed by researchers at the University of California, Davis and San Diego State University. Robosquirrel is currently in use and development in an interdisciplinary research project that uses biorobotics to investigate how communication between prey (e.g., squirrels) and predators (e.g., rattlesnakes) evolve in response to each other. It has received extensive science and popular media coverage. It stirred controversy when Senator Tom Coburn listed it in his Wastebook 2012 as a scientific research project that wastes United States federal tax dollars. Senator Coburn's release of Wastebook 2012 was quickly picked up by the popular media and the robosquirrel project was the headline of many media stories. The robosquirrel research project, in which robosquirrel is used and developed, has four aims: (1) to establish collaborations between ecologists and engineers to develop next generation robotic technology for studying predator-prey communication behavior, (2) to increase minority participation in science, (3) to develop public outreach, and (4) to support undergraduate and graduate education in biology and engineering. Currently, three versions of robosquirrel have been developed. It is currently funded by the National Science Foundation (NSF) based on peer review and by meeting criteria of intellectual merit and broader impacts required by NSF. The controversy focuses on the amount of money spent ($325,000) on robosquirrel. The researchers have responded that robosquirrel only cost a few hundred dollars and that approximately 70% of the funds are currently spent on training future biologists and engineers.

Robosquirrels

Background Donald Owings observed an interesting phenomenon during research in the field: when a California ground squirrel comes across a rattlesnake, it often raises its tail and waves it from side to side. In 2007, Owings (Department of Psychology and his graduate student at the time, Aaron Rundus, began collaborating with Sanjay Joshi (Department of Mechanical/Aeronautical Engineering) at University of California, Davis. They used an infrared camera to videotape how snakes and squirrels behaviorally interact. They found that a squirrel shunts blood to its tail and thereby heats it up when encountering a rattlesnake but not for non-poisonous snakes. Rattlesnakes were known to use infrared radiation to detect prey, but what they discovered suggests that the squirrels evolved the ability to communicate with rattlesnakes by heating up their tails and thereby signalling with infrared radiation. To test this hypothesis, they built a robotic squirrel (robosquirrel) that could behaviorally respond to rattlesnakes when they moved. They found that when robosquirrel waved a heated tail in response to the movement of a rattlesnake, the snake became defensive (i.e., it moved away from the robotic squirrel) rather than predatory. If robosquirrel waved an unheated tail, then the rattlesnake continued its predatory behavior. The next step was to determine whether squirrel behavior when rattlesnakes had not been encountered reduced the predatory behavior of rattlesnakes waiting in ambush. They video-recorded predatory behavior of rattlesnakes when ground squirrels flagged their tails. The researchers found that tail-flagging decreased the likelihood that rattlesnakes would strike and increased the likelihood that they would move away from that area. They found that California ground squirrels are actually performing two types of tail flagging: vigilance advertising and perception advertising. Vigilance advertising is hypothesized to occur when a squirrel enters an area that may contain rattlesnakes. By tail flagging, a squirrel may be signaling to a snake that it is vigilant and prepared to dodge any attacks. Perception advertising is hypothesized to occur when a squirrel encounters a rattlesnake and its tail flagging functions to signal to the snake that it is prepared to respond to attack and to warn other squirrels of the presence of rattlesnakes. To test these hypotheses about the function of tail flagging, they built robosquirrel to record encounters with rattlesnakes. Robosquirrel was programmed to wag its tail in the presence of a snake and its tail temperature can increase above its body temperature when it encounters snakes. The robosquirrel behaviors presented to rattlesnakes in naturalistic contexts can be precisely controlled. This control of behavior is impossible with living squirrels and so robosquirrel allows researchers to investigate how rattlesnakes respond to specific behaviors.

Versions

Laboratory RoboSquirrel The first robosquirrel was built using a taxidermically mounted adult female California ground squirrel. The tail was moved by a servo, which allowed robosquirrel to flag it tail at specified intervals. MATLAB software via a mini synchronous serial channel microcontroller, controlled the tail-flagging of robosquirrel. To control the temperature of the interior of robosquirrel’s body, a coiled Nichrome 80 resistance wire was inserted and a cartridge heater was inserted into its tail. The temperature of the Nichrome wire and the cartridge heater were controlled by thermostats wired with thermocouples that were placed inside its body and tail. Power to the two heaters was regulated via the thermostats by using a proportional-integral differential (PID) control loop to regulate the duty cycle of the power relays. An overhead camera videotaped the arena in which robosquirrel was mounted on a wooden stage beneath which were the theromostats and heater relays. A Rattlesnake was marked by attaching a small red light-emitting diode (LED) it. When a snake entered the arena, the images from the arena were analyzed by a program written in MATLAB that determined the distance between the squirrel and the LED. The program then calculated the rate of tail flagging based on the distance between the LED and robosquirrel. As the distance between the squirrel and LED on the rattlesnake decreased, robosquirrel increased its rate of tail flagging. The rates of tail flagging were based on previous field observations.

Field RoboSquirrels

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