Science

Squirrel-Snake Face Off!

• Fascinating
• Jaw-Dropping
• Weird

Are you afraid of snakes? How about venomous snakes? Most people turn the other way when they encounter a venomous snake. However, ground squirrels, unlike people, show no fear in the face of predatory rattlesnakes. Squirrels often approach snakes to within striking distance, kick dirt in their faces, and waive their tails back and forth (a behavior known as tail-flagging). This research project aims at finding out why squirrels approach snakes and tail-flag, behaviors that seem logically maladaptive.  

Ground squirrels have been in an evolutionary arms-race with rattlesnakes for thousands of years, one always trying to “one-up” the other. Squirrels have consequently evolved several defensives to combat the predatory rattlesnake:

1. Venom Resistance—adult squirrels are resistant to rattlesnake venom, but pups are not. Thus, snakes try to prey on vulnerable pups, and adult squirrels can safely harass nosey rattlesnakes
2. Skin on Fur—squirrels often take shed rattlesnake skin and rub it on their fur to hide their squirrely odor from hunting snakes
3. Turning up the Heat with Tail-flagging—squirrels approach snakes and tail-flag (side-to-side movement of the tail), but when flagging specifically at rattlesnakes they pump extra blood into their tails. This increases the heat in the tail and creates infrared light. Rattlesnakes are the only known vertebrate to detect such a signal because they have heat-sensing pits on each side of their face.

 Rattlesnakes have two things going for them in this face off:

1. They remain very very still and very very camouflaged when hunting squirrel pups. Thus, squirrels usually have a hard time knowing where snakes are, and snakes easily strike squirrels through surprise ambush attacks.
2. Their venom kills squirrel pups—once struck, pups are goners.

Purpose of this research:  We find this specialized snake-squirrel system very intriguing and we hope to learn more about coevolutionary processes by studying squirrel defenses and snake offenses.  One aspect that truly is confusing is the tail-flagging signal.  Why do squirrels tail-flag? And why do they use an infrared signal? What is the purpose of approaching a snake if it would be safer to stay away?  With your help, these are the questions we will answer.

Methods:  We are using very innovative technology to study these animals’ behaviors

1. ROBOSQUIRREL!—In collaboration with engineers at UC Davis, we have developed a biorobotic squirrel. Its outer covering is the skin of a real adult squirrel and inside it is heated by copper coils. Additionally, it can be controlled to tail-flag with or without infrared heat.  We keep it in squirrel bedding so that it smells like a live squirrel. Thus, it has the visual and thermal appearance, as well as the smell of a live squirrel. We will use this robot to see how snakes respond to tail-flagging with and without infrared heat.
2. Network Security Cameras—we use security cameras overlooking snakes in ambush (hunting) position to record strikes at prey and squirrel interactions. These cameras run over a wireless internet network so we can have interns at a central monitoring station watch all video feed in real-time (sort of like a mall surveillance room). These interns can control the cameras to zoom in on animals of interest and they can communicate to people in the field if a snake abandons its position. We use these cameras to keep a daily log of behavioral events for both snakes and squirrels, and to see how snakes respond to the robosquirrel presentations. This method of using security cameras is unique because we can continuously monitor animal behaviors with the least human interference as possible.

Project Significance:  This project will shed light on the coevolution between predator and prey by showing how selective forces shape animal behavior.  Since the rattlesnake and the squirrel are in an evolutionary arms race, we will be able to examine the strategies each opponent uses to “outwit” the other. For example, squirrels harass snakes, but how do snakes respond in order to be successful hunters?  It is a complicated process that involves evaluation and decision making by both opponents. This study aims at examining the decisions of both rattlesnake and squirrel as they face off in the match for survival.

Where will the Money Go?

All donations will go toward providing room and board to undergraduate research assistants. Every summer we take on 7 interns, future scientists eager to gain experience in conducting research. Together we can offer these students a once in a lifetime experience, without financial worry. By funding volunteers we will be able to conduct solid research and efficiently gather data to figure out why prey confront predators (sort of like why someone would taunt a bully) rather than running away.

 Thanks for supporting this #SciFund project!