RESEARCH ARTICLE Colony size does not predict foraging distance in the ant Temnothorax rugatulus: a puzzle for standard scaling models S. E. Bengston • A. Dornhaus Received: 14 April 2012 / Revised: 12 November 2012 / Accepted: 15 November 2012 / Published online: 25 November 2012 Ó International Union for the Study of Social Insects (IUSSI) 2012 Abstract Body size is often positively correlated with ecologically relevant traits such as fecundity, survival, resource requirements, and home range size. Ant colonies, in some respects, behave like organisms, and their colony size is thought to be a significant predictor of many beha- vioral and ecological traits similar to body size in unitary organisms. In this study, we test the relationship between colony size and field foraging distance in the ant species Temnothorax rugatulus. These ants forage in the leaf litter presumably for small arthropod prey. We found colonies did not differ significantly in their foraging distances, and col- ony size is not a significant predictor of foraging distance. This suggests that large colonies may not exhaust local resources or that foraging trips are not optimized for mini- mal distance, and thus that food may not be the limiting resource in this species. This study shows T. rugatulus are behaving in ways that differ from existing models of scaling. Keywords Home range Á Colony size Á Social insects Á Foraging behavior Introduction Foraging is one of the most thoroughly studied behaviors across all taxa. Organisms may vary in many aspects of foraging behavior such as selection of where to forage, what they are foraging for, when to leave a patch, and how far they travel to forage (Stephens and Krebs, 1986; Giraldeau and Caraco, 2000). When an individual decides how far to travel to forage, two main factors are often the most influ- ential: body size and environmental conditions. Body size is important to the biology of organisms as it impacts physiology, behavior, and natural history. Body size often is positively correlated with increased fecundity and survival (Wikelski and Romero, 2003), but trades-off with decreased performance in other aspects (Blanckenhorn, 2000). For example, an increase in body size often comes at the price of an increase in development time, meaning reproductive benefits are paired with an increased period of vulnerability. Another important effect of body size is that generally speaking, mass-specific metabolic rate tends to decrease as body size increases (Gillooly et al., 2001). In addition, as body size increases, so usually does the required home range of an organism (Swihart et al., 1988) which is thought to reflect the increased resource requirements of larger organisms (Jetz et al., 2004). This is a pattern seen interspecifically, such as the much larger brown bear (Ursus arctos) requiring a larger foraging territory than that of the American black bear (Ursus americanus) (Harestad and Bunnel, 1979), but also intraspecifically. Thompson et al. (1998) found that larger harbor seals (Phoca vitulina) for- aged farther from the coast than smaller conspecifics. Environmental conditions, predictably, also have a large impact on foraging distance. Patchy resources, competition, perceived threat and exposure to the elements all may influence how far an individual is willing to go for resour- ces. For example, Anderson (1986) found that several species of mice and vole will forage more than three times further when there is cover as opposed to open space. For- aging distance was also impacted by the depth of snow, ambient temperature, and the food supply suggesting that both perceived risk and metabolic expenditure impact how the individuals were making foraging decisions. S. E. Bengston (&) Á A. Dornhaus Department of Ecology and Evolutionary Biology, University of Arizona, P.O. Box 210088, Tucson, AZ 85721-0088, USA e-mail: bengston@email.arizona.edu Insect. Soc. (2013) 60:93–96 DOI 10.1007/s00040-012-0272-4 Insectes Sociaux 123