In Tuva, the breeding season of Campbell's dwarf hamster begins in April, and in Mongolia, it begins in at the end of April or the beginning of May.[28][29] However, in all distribution ranges, it ends in late September or early October.[30] In captivity, Campbell's dwarf hamsters breed throughout the year, with no fixed breeding season, but a large number are born in the summer months. In the wild, three to four litters are produced each year, with an average of eight offspring per litter.[24][25][30] In captivity, females can have between one and 18 litters per year, with one to nine offspring per litter.[18] In captivity, the gestation period for Campbell's dwarf hamster is between 18 and 20 days, and the shortest gestation period recorded for a captive female was 13 days.[24][30] The male hamster is likely to assist the female during birth. The male may pull the offspring from the birth canal, clean them, or collect food for the mother and offspring.[31]
When the offspring are born, they are hairless and have a body mass of approximately 1.5 g (0.053 oz). Incisors and claws are already formed, but the digits, eyes, and pinnae are closed and cannot be used. The rate at which the young develop differs depending on the distribution range. However, the differences are usually no longer than a day. In Tuva, the pinnae open on the first day of birth and are completely open after three days of development. However, in Mongolia, the same process occurs between two and four days of development. Fur first grows on the crown, back, and abdomen. The young are usually have a full coat of fur after seven days of development.[30] Offspring born in captivity have a shorter development time than those born in the wild. Specifically, the growth and development of the head and body, tail, hind feet, and pinnae can be up to a day sooner than those found in the wild. After 28 days of development in captivity, the young are already around half the mass of their parents.[15]
In captivity, females become sexually mature at two months of age. The ovarian follicle forms about 16 days prior to the birth of the offspring. After mating, female hamsters typically have larger uteri, ovaries, and adrenal glands compared to females which live alone, with other females or those that have not mated. The females and males may fight each other when getting to know their partner.[8] Also, these females have a shorter gestation period, around four to five days.[7]
Hybrids Edit
In captivity, only Campbell's dwarf hamsters and Djungarian hamsters are able to interbreed and produce live offspring or hybrids. Although hybrids make suitable pets, the breeding of hybrids and cloning can cause health problems, due to inherited diseases. Because genetic information can be very similar, genetic health problems or vulnerabilities can easily be inherited by the offspring. The widespread breeding and distribution of hybrids could threaten the existence of both pure species and subspecies of the ecosystem. This could ultimately lead to the extinction of the subspecies. Each litter becomes smaller as more generations are produced and the young commonly begin to inherit many congenital problems.[23][32]