Attenuation and reacquisition of foraging behavior in a patchy environment.

The present experiment examined the attenuation and reacquisition of foraging behavior of pigeons on a restricted diet. Using the procedure of Roberts (1988), thirty-two feeders were arranged in four circular patches of eight feeders each. The feeders were baited so that each patch contained a different density of food. Pigeons learned to forage among the patches. During this initial acquisition phase, visits to the patches by the pigeons differed as a function of the food density of the patches. After this initial foraging training phase, each pigeon received one of two response elimination procedures. For half of the subjects, food was not present during the response elimination phase. For the remaining subjects, food was placed exclusively outside the patches during this phase. Foraging behavior decreased quickly and somewhat similarly for both conditions. During a final phase in which the retraining of the original foraging behavior occurred, the group given food outside the patches during response elimination provided evidence of superior foraging with respect to sensitivity to the different patch food densities. The results are discussed with regard to previously published response elimination effects.

Ureteroarterial fistula.

Among the many complications of total pelvic exenteration is a fistulous communication between the iliac artery and ureter. We reported 1 such case complicated by near exsanguination and shock. Repair of the fistula was accomplished by closure of the iliac rent and cutaneous ureterostomy.