As a part of her Master’s degree in Environmental Science, recent graduate Vanessa Velasco ’15 completed her thesis titled, “Investigation of Non-Lethal Electric Shock on American Crows as a Predator Aversion Treatment for Reducing Depredation on California Least Tern Eggs.” Velasco developed a predator aversion technique to deter American crows from consuming federally endangered California least tern eggs at the enclosed nesting site at Venice Beach, California.
The California least terns that nest in the Venice Beach colony had not been able to successfully reproduce from 2009-2013 mainly due to 100% egg predation by American crows. Velasco’s thesis studied the response of American crows to negative conditioning from electrified least tern eggs. The eggs were created by emptying actual least tern eggs of their contents and filling the interior with conductive material that was connected to an electric fence energizer. The modified egg was placed on the sand at the Venice Beach colony above a buried steel plate that was also connected to the electric fence energizer. The crows received a non-lethal electric shock when they stood on the sand above the electrically charged steel plate and pecked at the electrically charged egg, thus completing the electric circuit.
Each nest was under video surveillance from a nearby motion sensor game camera. The electrified egg system and game cameras were deployed throughout the least tern nesting season which ranged from April to September of 2014. The data from the footage was analyzed with conditioned crows defined as crows that were present within 15 feet, but not less than 1 foot from the electrified eggs. Unconditioned crows were those crows observed within 1 foot of the electrified eggs. Statistical analysis showed the number of conditioned crows observed in the video clips significantly differed from a homogenous distribution using a chi-square test (p<0.001). The largest number of unconditioned crows was observed in the first 5 weeks of the experiment and conditioned crows increased as the experiment progressed. The 2014 season was also the first year in the recent 5 years that the Venice Beach colony successfully produced fledges.
Initial results are encouraging and the California Department of Fish and Wildlife (CDFW) is working with the Center for Urban Resilience at Loyola Marymount University (LMU) to produce additional multi-year research. If successful, CDFW may implement the predator aversion technique as a management tool for conservation. Research that was initially started as a student project may have the potential to benefit a local endangered species population.