Agonistic behavior between wild and genetically sterile male Norway rats (rattus norvegicus)

Genetically sterile male Norway rats, Rattus norvegicus, were tested in the laboratory to determine both 1) behavioral characteristics, and 2) the ability of sterile males to compete aggressively and sexually with wild Norway rat males. Sterile males were larger in weight, more frequently dominant, won as many fighting encounters, were as aggressive as wild males, and mounted females more frequently. Behavioral activities were similar for both strains when compared under laboratory conditions with no apparent abnormal behavior exhibited by the sterile males. Use of sterile males in biological control programs is discussed.     

Growth and social behavior of previously undernourished mice

Developing mice were growth-retarded by underfeeding of their mothers during lactation. Control mothers were well nourished throughout. All offspring were fed ad libitum from weaning till their behaviour was tested in adulthood. The undernourished mice had weight deficits at weaning of 49% compared with controls. Nevertheless, they showed partial catch-up growth thereafter, in that their absolute weight deficits decreased between weaning and adulthood. Social behaviour observations were made on pairs of mice of the same treatment group. Previously undernourished mice were slower to start attacking one another, spent more time near or in contact with one another and did less tail-rattling than their controls.