DISSERTATION RESEARCH: The Consequences of Food Assessment and Cache Placement on Social Competition and Cache Pilfering in a Scatter-hoarding Tree Squirrel

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

Many animals hoard their food, hiding food items in various locations in order to retrieve them at a later date, for example, when resources are scarce. Scatter-hoarding animals store each food item in a different location and often engage in protective behaviors that may prevent their food stores (caches) from being stolen. These behaviors include handling food items extensively before burying them, travelling away from competitors to bury food, and carefully covering caches. Scatter-hoarding fox squirrels (Sciurus niger) perform unique behaviors (head flicks, paw manipulations) that allow them to determine the weight and value of individual food items and protect their caches accordingly. By using Global Positioning System (GPS) and tracking technology, behavioral observations, and DNA testing, the researchers will explore how these food protection behaviors contribute to successful cache retrieval or prevent theft of caches by other squirrels. This study also will explore whether individuals are more or less likely to steal from their relatives. The proposed research will fill a gap in the animal behavior literature by advancing our understanding of how animals recover food they have buried, and illuminating whether scatter-hoarding animals provide for their offspring or close relatives by allowing theft of their caches. Studies of scatter-hoarding animals have yet to address key questions: do cache protection strategies deter theft by pilferers and help scatter-hoarding animals recover their caches? Fox squirrels (Sciurus niger) perform unique assessment behaviors (head flicks, paw manipulations) that allow them to adjust investments in caches. The proposed studies will determine how a squirrel's assessment of food is related to its investment in a cache, and whether these behaviors reduce pilferage. This study will use GPS data and radio-telemetry/passive transponders to measure caching and pilfering behavior. They will also amplify and sequence established microsatellite loci to estimate genetic relatedness and incorporate relatedness into models of cache retrieval and pilferage. Food-storing animals engage in cache protection behaviors because theft is common. Previous studies have failed to examine the complex relationship between food assessment, cache protection, social context and the long-term fate of caches. Moreover, most studies utilize artificial caches made by humans or laboratory animals. This field study will use an innovative, interdisciplinary approach to examine the pilferage of caches made by free-ranging squirrels. This study also will examine the relationship between kin selection and pilferage tolerance, support for which would have major implications for our understanding of scatter-hoarding and social behavior. All data and analyses will be made available via published manuscripts, conference presentations, reports to the NSF and otherwise as suggested by NSF guidelines.