HOARDING BEHAVIOR IN OBESE AND CONTROL RATS - EVIDENCE INDICATING COST DIFFERENCES

Hoarding behavior of rats can be described by the equation: y = ax + b , where y is the amount of food hoarded, x the rat's body weight, a th e negative slope of the regression line, and b, the ordinate at zero a bscissa. We repeatedly evaluated the parameters of this equation in si x obese Zucker rats and six controls, from 8 to 32 weeks of age. The m ean slope of the regression lines remained close to -11 in both groups of rats, until 24 weeks of age. From then on, the slopes of the obese rats decreased dramatically to c. -3, and remained as such for the re st of the experiment, while that of controls remained constant. At thi s age (24 weeks), controls weighed 453 +/- 14g and obese rats 729 +/- 18 g. We suggest that the decreased slope of hoarding in obese rats wa s due to an increased cost of the hoarding behavior. (C) 1998 Academic Press.