Abstract
Timed matings of mice are often carried out to obtain offspring of a precise age when required for a study. Timed matings involve housing male and female mice together for a limited time period, typically overnight. A limitation of this practice is that many mouse pairs fail to mate during the brief co-housing period. The authors co-housed each breeding pair in the same cage but separated by a transparent partition for 3 d before carrying out timed matings. This co-housing strategy resulted in increased copulation during the timed mating period and also significantly increased the average number of pups produced per breeding pair. The authors suggest that co-housing likely permits male urine-borne pheromones to induce female estrus and also enables the expression of male and female mating behaviors.