Zausinger, P., Schneider, B. M., Bauer, A. et al. 2022. Short communication: Do the tameness of the dams and the sex of the offspring have an influence on the “gentling” effect in laboratory rats? Journal of Veterinary Behavior 52-53, 45-49.

“Gentling” (soft touching, “taming”) has long-term effects on the behavior of laboratory rats (Rattus norvegicus). Our own studies showed that the use of a “gentling” program in the fourth and fifth week of life resulted in a significant reduction in fear behavior towards humans up to the age of 6 months. However, our investigations have so far only considered female animals. In the current study, we therefore wanted to determine whether there also is a long-lasting “gentling” effect in male rats. In addition, we intended to investigate whether there is an impact depending on the level of tameness of the mothers. We mated 14 female rats, which we selected from our previous experiments based on their behavior, with one male rat. Five females became pregnant and had litters (2 “tame” dams had 13 pups and 3 “not tame” dams had 18 pups). The 31 pups (16 female and 15 male rats) were divided into a “gentling” group (n = 16) and a “not gentled” group (n = 15). The previously developed “gentling” program was applied to the “gentling” group. That means the pups were gently touched, hand-fed and talked to during their fourth and fifth week of life (10 minutes per cage twice daily over a period of 14 days). The “not gentled” group did not receive any treatment. To evaluate the “gentling” effect on tameness, behavior tests according to our previous study were performed at the ages of 6, 8, 10, 14 and 16 weeks and 6 months. The experiments were blinded regarding parentage and treatment. The behavior tests revealed that the “gentled” rats were “tamer” than the “not gentled” rats. With Westfall correction for multiple testing, the estimated significant differences lasted up to the 30th week of life and therefore exceeded the results of our previous study. The “gentled” pups of the “tame” dams rendered better results than the “gentled” pups of the “not tame” dams. The female rats improved with increasing age and test experience, but the male rats did not. The results show that this “gentling” program reduces the fear of humans even in male laboratory rats and that the tame nature of the mothers affects the “gentling” effect in the offspring.