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- Title
THREAT OF PREDATION AND FORAGING BEHAVIOR IN URBAN FOX SQUIRRELS.
- Authors
Tatina, Robert
- Abstract
Previous studies have shown that animals foraging in artificial patches quit feeding at higher giving up densities (GUDs) of food in risky locations compared to safe locations. Risky locations are those at which threats of predation are high. The purpose of my study was to determine if foragers, specifically urban fox squirrels (Sciurus niger), change their food preference under risk of predation. For 40 days in winter 2007-2008 in Mitchell, South Dakota, I exposed random combinations of sunflower fruits and seeds to squirrel foraging in four trays. Two trays were placed in a yard (risky location) into which a dog was periodically released. Two others were placed outside the yard (safe location), a location to which the dog had no access. At the end of each day I weighed seeds and fruits separately; these weights were the GUDs. The GUDs for each food type from risky and safe locations were compared using a Student's t-test. I also determined partial preference for fruits for each day in each tray and compared these using a Student's t-test. Mean GUDs for sunflower fruits from the risky location were 4.48 ± 0.91 (se) and 4.44 ± 0.91 (se). These were significantly greater than mean GUDs (1.58 ± 0.40 (se) and 1.67 ± 0.49 (se)) from the safe location (t = 4.85, df = 121, p = 0.0001). Likewise, mean GUDs for sunflower seeds from the risky location (10.11 ± 1.86 (se) and 10.09 ± 1.82 (se)) were greater than mean GUDs (4.56 ± 0.83 (se) and 5.56 ± 1.48 (se)) (t = 4.25, df = 136, p = 0.0001) from the safe location. Mean partial preference for fruits (PPF) in the risky location was 0.553 ± 0.018 (se) which was significantly greater than 0.500 (z = 7.67, N = 53, p = 0.00001). Mean PPF in the safe location was 0.590 ± 0.009 (se), also significantly greater than 0.0500 (z = 14.02, N = 61, p = 0.00001). PPFs were not different between the risky and the safe locations (t = 1.87, df = 79, p = 0.066). When urban fox squirrels foraged in the risky location their GUDs were higher than for the safe location because they balanced foraging against predator vigilance. However, they did not change their food preference. Natural selection has conserved that foraging behavior which is optimal (i.e., yields a net energy gain) regardless of the riskiness of the foraging location.
- Subjects
MITCHELL (S.D.); SOUTH Dakota; FOX squirrel; FORAGING behavior; PREDATION; FOOD preferences; SURVIVAL behavior (Animals); NATURAL selection
- Publication
Proceedings of the South Dakota Academy of Science, 2008, Vol 87, p336
- ISSN
0096-378X
- Publication type
Article