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Nordell poster x abs 2011 for printing

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Shawn Nordell

Squirrels modify their caching behavior when they hear blue jay vocalizations nearby. In experiments where squirrels were given nuts near a speaker playing either blue jay or robin calls, squirrels cached fewer nuts and carried nuts farther from the speaker when they heard blue jays compared to robins. Squirrels appeared to learn about the presence of potential cache-robbing blue jays from their vocalizations and alter their behavior accordingly to reduce cache losses.

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Blue jays affect the caching behavior of eavesdropping squirrels Shawn E. Nordell, Thomas J. Valone, Courtney A. Harrington , & Tina Mozelewski Department of Biology, Saint Louis University, St. Louis, MO 63103 ABSTRACT Individuals can gain important information about their environment by eavesdropping on interactions between others. We examined whether gray squirrels learn about the presence of blue jays by hearing their vocalizations. Because blue jays are important food cache robbers, we predicted that squirrels would modify their caching behavior to reduce cache losses when jays are nearby. Squirrels were provided with a small pile of cacheable hazel nuts placed at the base of a tree in two treatments. In one, blue jay vocalizations were played from a speaker located 15 m from the food. In the control treatment, the songs of American robins, a non-cache robber, were played. We recorded whether each nut was eaten or cached, the distance carried prior to eating or caching and the direction moved relative to the speaker. When jay vocalizations were played, squirrels cached fewer items and carried them farther from the speaker compared to the control. There was no difference in direction moved between treatments. Our data suggest that squirrels learn about the presence of jays by listening to their vocalizations and modify their behavior to reduce the likelihood of losing their caches. RESULTS indicates graduate student indicates undergraduate student Acknowledgements: Thanks to the Saint Louis University Animal Behavior Class for working on the experimental design for this project. INTRODUCTION Gray squirrels ( Sciurus carolinensis ) cache food for future use. Caches can be robbed by competitors, including blue jays ( Cyanocitta cristata ) Hypothesis: Squirrels should eavesdrop on blue jay vocalizations to detect their presence nearby, and modify their caching behavior to reduce the likelihood of pilferage. Prediction: When squirrels detect Blue jay vocalizations they will: a) cache less and so consume more food items immediately because the probability of cache robbing is high; b) travel farther to cache away from the potential cache robber to minimize cache robbing; c) travel away from the direction of jay calls to minimize cache robbing. METHODS Pile of hazelnuts at base of tree (October through January). Place speaker 15m away. Play jay calls (potential cache robber) or robin calls (control non-cache robbing species). Record : # nuts cached and eaten Distance traveled to make cache Direction of cache relative to speaker CONCLUSIONS Squirrel caching behavior is affected by the presence of jay vocalizations: individuals travel farther before caching during jay calls. Squirrels do appear to cache less in the presence of jay calls but additional data are required to better test this. Figure 1 The squirrels cached fewer food items during jay calls. Figure 2 The squirrels traveled farther to cache during jay calls (t-test, p < 0.05). Figure 3 - The squirrels primarily cached away from the speaker in both treatments.

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Nordell poster x abs 2011 for printing

  • 1. Blue jays affect the caching behavior of eavesdropping squirrels Shawn E. Nordell, Thomas J. Valone, Courtney A. Harrington , & Tina Mozelewski Department of Biology, Saint Louis University, St. Louis, MO 63103 ABSTRACT Individuals can gain important information about their environment by eavesdropping on interactions between others. We examined whether gray squirrels learn about the presence of blue jays by hearing their vocalizations. Because blue jays are important food cache robbers, we predicted that squirrels would modify their caching behavior to reduce cache losses when jays are nearby. Squirrels were provided with a small pile of cacheable hazel nuts placed at the base of a tree in two treatments. In one, blue jay vocalizations were played from a speaker located 15 m from the food. In the control treatment, the songs of American robins, a non-cache robber, were played. We recorded whether each nut was eaten or cached, the distance carried prior to eating or caching and the direction moved relative to the speaker. When jay vocalizations were played, squirrels cached fewer items and carried them farther from the speaker compared to the control. There was no difference in direction moved between treatments. Our data suggest that squirrels learn about the presence of jays by listening to their vocalizations and modify their behavior to reduce the likelihood of losing their caches. RESULTS indicates graduate student indicates undergraduate student Acknowledgements: Thanks to the Saint Louis University Animal Behavior Class for working on the experimental design for this project. INTRODUCTION Gray squirrels ( Sciurus carolinensis ) cache food for future use. Caches can be robbed by competitors, including blue jays ( Cyanocitta cristata ) Hypothesis: Squirrels should eavesdrop on blue jay vocalizations to detect their presence nearby, and modify their caching behavior to reduce the likelihood of pilferage. Prediction: When squirrels detect Blue jay vocalizations they will: a) cache less and so consume more food items immediately because the probability of cache robbing is high; b) travel farther to cache away from the potential cache robber to minimize cache robbing; c) travel away from the direction of jay calls to minimize cache robbing. METHODS Pile of hazelnuts at base of tree (October through January). Place speaker 15m away. Play jay calls (potential cache robber) or robin calls (control non-cache robbing species). Record : # nuts cached and eaten Distance traveled to make cache Direction of cache relative to speaker CONCLUSIONS Squirrel caching behavior is affected by the presence of jay vocalizations: individuals travel farther before caching during jay calls. Squirrels do appear to cache less in the presence of jay calls but additional data are required to better test this. Figure 1 The squirrels cached fewer food items during jay calls. Figure 2 The squirrels traveled farther to cache during jay calls (t-test, p < 0.05). Figure 3 - The squirrels primarily cached away from the speaker in both treatments.
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