Another study to show that transplanting young ovaries into old mice extends life quite significantly: "successful ovarian transplants increased the lifespan of the mice by more than 40% ... All the mice in both experiments that had received transplants resumed the normal reproductive behaviour of young mice. They showed interest in male mice, mated and some had pups. Normally, old mice stay in the corner of the cage and don't move much, but the activity of mice that had had ovarian transplants was transformed into that of younger mice and they resumed quick movements. Furthermore, the lifespan of the mice who received young ovaries was much longer than that of the control mice: the mice that had received two ovaries lived for an average of 915 days, and the mice that had received one ovary, for an average of 877 days. The newest of our data show the life span of mice that received transplants of young ovaries was increased by more than 40%. ... The average normal lifespan for this particular breed of mice [is] 548 days. ... it was not known why the ovarian transplant increased the lifespan of the mice, but it might be because the transplants were prompting the continuation of normal hormonal functions."