Bedding soiled by male affects litter size study

https://link.springer.com/chapter/10...4757-9655-1_41

"Exposing females to male soiled bedding resulted in a significant increase in both the number of implantation scars (12.2 ± 0.47 compared to 14.2 ± 0.34) and litter size (11.6 ± 0.49 compared to 13.0 ± 0.50). The number of scars represents the number of embryos implanted and exceed litter size because of intrauterine wastage. The mean weights of the pups did not differ between groups and, thus, increased litter size following male stimulation was accompanied by a higher total weight of the litters. Therefore, exposure to male soiled bedding increased litter size without a reduction in the body weight of the pups."

According to this research changing the bed often may reduce litter size. If the female mice are introduced to the male soiled bedding more their litter size increases.