Both sexes become sexually mature when they are one to two years old. Oestrus in females lasts one to four days; it typically occurs once or twice a year, though it can occur three or four times a year if the mother loses her litters.  Observations of captive servals suggest that when a female enters oestrus , the rate of urine-marking increases in her as well as the males in her vicinity. Zoologist Jonathan Kingdon described the behaviour of a female serval in oestrus in his 1997 book East African Mammals . He noted that she would roam restlessly, spray urine frequently holding her vibrating tail in a vertical manner, rub her head near the place she has marked, salivate continuously, give out sharp and short "miaow"s that can be heard for quite a distance, and rub her mouth and cheeks against the face of an approaching male. The time when mating takes place varies geographically; births peak in winter in Botswana, and toward the end of the dry season in the Ngorongoro Crater . A trend generally observed across the range is that births precede the breeding season of murid rodents.