>GETTING STARTED<

For specific reproductive morphology, visit the appearance section.

GUIDE TO DETERMINING THE SEX OF DEGU ADULTS AND PUPS

Degus are usually fully adult at around 53-55 weeks old22 and at this age are generally fully reproductively competent. The average age of first conception in wild degus is 6 months51 , 52, but this can vary between 45 days to 20 months52! The average weight (of the female) at first conception in the wild is 205 g52, however it is strongly recommended to wait until the female weighs 220 g or above before starting to breed from her in a controlled captive breeding programme.

Until recently, it was thought that female degus were induced ovulators36 , 133 and that prior to breeding, the females need to be placed near to a male so they could see, hear and smell him. This was assumed to be because females would only become fertile in the presence of a male36 , 52. However, there is growing evidence to suggest that female degus do not require presence of a male to begin oestrus, as many captive female-only groups will enter oestrus spontaneously during breeding season. However, before breeding it is recommended the male(s) be housed close to the female enclosure in order for them to gain familiarity and facilitate positive interactions during breeding sessions.

In wild degu colonies, the breeding season on average starts when it begins to get light at 07:00h and dark at 19:00h22 (about 12 hours light:12 hours dark). This usually coincides with the start of winter coat shedding around May-June23. However conception (fertilisation) typically occurs around September-October23, but can occasionally occur again in December-January as a result of the female post-partum oestrus23 , 52 (see below). Breeding times in captivity can be highly variable, especially as pet degus in the northern hemisphere52 are often able to breed throughout the year36 , 51 , 52 due to spontaneous oestrus. For captive colonies in the northern hemisphere, breeding season typically begins around late winter and lasts until mid to late spring when pups are born170. Female degus have a three-week oestrus cycle40 and will often become more active on the day of oestrus40, a good indicator to you that she is receptive. Her body temperature may also rise (up to 4ºC)40, this is due to the higher levels of the hormone oestrogen in her blood stream40. During her season, the female's vulva visibly opens108 , 133 , * , 170, which is caused by the perforation of the vaginal membrane133. It remains open for some weeks, until the end of her season133 , *. This is not caused by male penetration, as it occurs in all oestrus females*.

Interestingly, male degus' testosterone levels rise during the breeding season106 , 107, giving a greater chance of fertilisation during this time. It is also suggested that social stimuli may activate testosterone secretion107. Unfortunately it has also been found that captive males often have reduced testosterone levels compared to wild males in general106. Captive male degus will increase their daily metabolic rate during breeding season independently of social interactions107. Age may also affect testosterone and breeding performance107.

You may notice your degus dustbathe more frequently around breeding season22. This can be a good indicator of when it's a good time to breed your degus. Before breeding degus you should slightly increase the amount of food your male degu gets, as males use more energy during reproduction than females28. Breeding is actually a very relaxing time for both male and female degus, as this is when cortisol (stress) levels are the lowest37. In males, this drop in cortisol allows higher testosterone levels to trigger spermatogenesis37. It is therefore important to make sure your male degu is stress-free in order to insure he is fertile.

The female's vagina closes soon after mating52. This is facilitated by the formation of a mucous/semen 'plug' that sits inside the vagina* , 133, blocking entry to the cervix. This plug acts as a protective barrier for the developing foetus against external bacteria*, and it is also hypothesised that it acts as a 'safeguard' for the male's fertilisation*. Subsequent matings after the plug has formed however, will result in the plug becoming dislodged from the female as the male withdraws his penis*. The vagina has also been observed to open sporadically throughout gestation133.

Blastocysts may be found in the uterus 4-5 days after mating135, implantation of the embryo occurs by the seventh day post fertilisation52 , 135, with an unusual (interstitial135) attachment of the ectoplacental trophoblast to the maternal tissues52. Amniotic cavity and allantois are formed at days 12-13 and 30 post copulation, respectively135. The chorio-allantoic placenta is formed 30-35 days after mating135 (see appearance section for specific placenta details). The amnion is avascular and is formed by cavitation135.

Female degus are pregnant for about 3 months23 , 28 , 31 , 108 (86-93 days36 , 52 , 108 , 133) which is a relatively long time108; the reason is that pups are born with an unusually high degree of development170 , 28 , 108, and may also be due to the unusually slow rate of fetal growth135. It has been suggested that pups born in captivity in Britain are markedly less developed at birth compared to degu pups in the US, as judged by delayed eye opening and poor fur coverage15. However recent evidence has found British pups to be born with a full coat of pup fur and open eyes a few hours after birth, just the same as wild pups170.

>BIRTH<

Females will give birth to around 3-10 23 , 31 , 36 , 52 , 133, with an average of 6 pups per litter23 , 30 , 104 , 36 , 52. The sex ratio is around 100 females to 110 males52 , 133. The number of pups produced per litter can be as low as one single pup or as many as 12170, although these cases are uncommon.

24 hours after giving birth, the mother will be slightly heavier than her usual, unpregnant average weight23 , 170. It's a good idea to weigh the mother at this time to check her weight, and weigh her frequently in the following weeks until she has returned to her normal weight. In this way you can keep a check on any problems she could have before they become serious. The mother's weight increases during pregnancy and remains high during lactation37 (although it will slowly decrease over the first 2 weeks170) as she will eat more, increase her fat stores and increase the mass of organs such as the liver during this time162. Her resting metabolic rate will also increase162. Newborn pups will begin suckling within hours of birth, lying on their back132, guided to their mother's nipples by the mammary hormone released from the nipple tissue105. Antibodies from the mother are passed on to her own pups, both during pregnancy and lactation131, to help immune system development.

Your newborn degu pups need a lot of care in their first weeks of life. You must be very careful not to stress the pups during this time, as early adverse emotional experience can alter the development of the pups' brains13 , 110 , 149. This can cause physiological and cognitive deficits in later life18 , 164, similar to ADHD, depression and anxiety in humans, which are irreversible164, particularly if separated from the mother for any length of time110 , 149. The first three weeks are critical to the degu's normal development18. During this time handling should be minimised to avoid stress18. After this time, research has shown that handling the pups but NOT removing them from their mother does not have severe detrimental effects31. However continual handling at a young age has been shown to alter juvenile behaviour31. Research has shown that lactation and child rearing is also highly stressful to the mother37, so care should be taken not to cause her undue disruption. This stress is related to high production, energy utilisation and body mass37.

You must never remove newborn pups from their mother for any period of time. The pups need to hear their mother's voice as this soothes them and prevents developmental dammage13 , 31, whilst stimulating physical and mental development31. Similar to human babies, pups learn to recognise and respond to their mother's call within the first days of life18. Removing pups from their mother is also a traumatic emotional experience for them18 , 110 which can damage the developing limbic system18 in the brain. Their mother is also essential for providing warmth for the pups as they cannot regulate their own body temperature until they are around eight to twenty days old52 , 108. Interestingly, the pup's fur at birth allows a heat saving of 7.78 calories per degree centigrade per hour52.

Newborn degus have an average weight of 14.6 g15 , 36 , 52 , 104, although this can vary between 8-17 g170, which is around 5-6 % of maternal body mass170. You should carefully weigh each pup while the mother is present a few days after they are born, and then weekly until fully weaned. Pups grow at a rate of 1-3 g per day over the first two weeks170, and between 5-15 g per day between the ages of 2-6 weeks170. Pups will exhibit the largest body mass increase between the ages of 4 and 8 weeks68. There is also a rapid increase in the thermoregulatory ability of pups at room temperature when they are in the weight range of 24-25 g52, a weight which is said to be a key threshold in the pup's development52. Pup weight-age tables can be found here. Degus are born fairly precocious23 , 28 , 170 (i.e. well developed), as they are born with open eyes and ears31, upper and lower fur and pigment, and teeth15 , 31. This is probably a result of a combination of factors, including communal nesting in the wild23. However, the degree of development can be highly variable, depending on individual, environment and conditions51. Newborn pups' sensory systems are so developed that they can respond to familiar and new environmental stimuli from birth18 , 31. Degus are able to walk supporting their full weight within 3-4 hours of birth15 and are also able to right themselves, sit up on their haunches, rear upright and vocalise15. By the first or second day of life, pups are able to functionally groom, including face washing, hind paw scratching and rapid head shaking15. Behaviour patterns including play and dustbathing are shown to develop rapidly during the second week after birth52. Play is almost exclusively family oriented and involves frequent body-nose contact52. Interestingly, male pups, on average, weigh more at birth and grow at a faster rate than female pups170, despite the lack of size differences in adulthood.

Baby degus can be raised by both parents30, however it is very important to separate the male from the mother as soon as she has given birth, for a few days. This is to prevent him mating with her during her short post-partum oestrus23 , 133 where she could become pregnant again during this time. Becoming pregnant again so soon after the first litter would not only be very stressful for the female, but also extremely dangerous for her health, and the health of any pups born in the 'backlitter'. It is strongly advised to let breeding females have no more than one litter per year in order to allow their bodies plenty of time to recover. Although the postpartum oustrus lasts only four days on average, it is recommended that the male be separated from the mother for one week after birth to be absolutely safe. After a week, the male can safely be put back with the female and the pups. The father (and indeed any males present in the group) will participate to a great extent with raising the pups31. Rearing the pups with the mother and father (or other females) relieves some of the stress for the mother and the burden is shared. It has been observed that pups reared with both parents huddle less with the mother14, giving her more 'time off'. During growth, interaction of the pups with their parents is a very important factor as it is the pups' earliest emotionally modulated learning process, or 'filal imprinting'18. Pups have specific ways of responding to cues from their parent which are critical for physical and psychological maturation18. It is interesting to note that disturbance of pup-parent interaction leads to 'hospitalisation syndrome' which results in permanent deficits of vocal behaviour, personality development, intellectual/social capacity and mental disturbance18. It is therefore better to allow pups to develop normally by allowing the positive emotional experience of developing strong emotional bonds to both parents18. However, female degus also nest communally (see below), and allowing the mother to raise the litter with only the other females in the group (breeding or otherwise) fulfills just the same requirements.

Both parents will look after the young by huddling and squatting14 , 132 in order to keep the pups warm. Parents will spend around 80 % of the day close to the pups, either beside them or covering them23. The parents will also interact with the pups by using social behaviours such as body-nosing14, sniffing, licking and carrying32 the pups. Typically, the father will spend less time on average with the pups than the mother14. However, it is interesting to note that as the pups begin weaning and become less dependant on their mother, the amount of mother-young contact decreases, but the amount of father-young contact increases during this time14.

Pregnant females living with other females (pregnant or not) can be kept together. Both male and female degus which are unrelated to the pups do not show aggression toward unfamiliar pups32. Once the pups are born, females living together will spontaneously nest communally23. This involves a female who is not the birth mother looking after (and suckling23 if she is lactating) any number of pups. This is beneficial to the pups as if they are nested with two or more females, pups spend less time alone and are cared for more often than pups housed with the mother alone23. In fact, pups have been shown to spend more time with a lactating female43 (compared with their mother) due to the curiosity of the pups towards the novelty of the lactating female43. You should slightly increase the amount of food you give to all lactating females, as more energy than normal is used in producing milk28. Communal care helps promote survival of the pups and helps the pups maintain their body temperature23. Species (such as the degu) that communally nest are termed 'plural breeders' and is not common among rodents, although the sub-order most commonly demonstrating this are caviomorphs23, to which the degu belongs.

>WEANING and GROWTH<

After birth, pups drink their mother's milk alone which gives them all the nutrients they require108. However, newborns may be seen to chew substrate15, possibly as chewing practice. Similarly, 3 day old pups may gnaw droppings15 but this also helps the pups to colonise their intestines with microflora and 'friendly' bacteria in order to aid digestion. The first solid food is usually ingested when the pups are around 6 days old15 , 104, but cannot be properly digested until the pups are around 15 days old108.

Pups require suckling for at least 3 weeks28 in order to gain strength and immunity. Captive degus will nurse their young for 21-28 days on average (days of weaning)31 , 104, consisting of three stages; early (days 5-8), middle (days 15-21) and late (days 26-40)108. In practice, this can vary between 2-6 weeks51, but it is more beneficial to the pups to allow weaning to occur at 4-6 weeks52 , 132. Mothers will actually continuously lactate for 35-40 days104 , 108, which is a relatively short time108. The mother will convert food eaten almost immediately into milk108. Degu milk is relatively dilute and has a stable solids, lipid, protein, ash and energy content108, however the carbohydrate content will decrease significantly from early to late lactation108. This is most likely to relate to the pups' initial precocial nature and high energy requirement108, and the fact that they do not start eating solids until relatively late post partum108.

During the weaning process, the pups gradually replace their intestinal lactase enzymes (those used for digesting milk) with sucrase enzymes (for digesting hard feed)34. This process is a slow one34, hence it is essential that the pups suckle for at least three weeks in order to allow this change to fully occur. It is also during weaning that pups build up their intestinal bacteria, which is essential for their adult digestion104. This is one of the reasons why degus have such a lengthy weaning period104. You may want to provide weanlings with small quantities of fresh grass, as has been observed in the wild52.

Once lactation is over, cortisol (and so stress) levels decrease greatly in the mother37.

As the weeks go by, you will notice that the sibling pups increase the amount of interaction with each other14. This is a process of strengthening the bonds between siblings and it continually increases postnatally14. However, when the pups are separated from the parents, the interactions may increase14 as the parents are no longer able to keep them in check! Care must be taken not to expose pups to a new environment too early as this can cause changes in the behavioural development of the degu18. New environment exposure and separation from parents and siblings causes a heightened arousal and emotional stress in juvenile degus18.

You may notice that young degus quickly learn to explore and become braver away from their parents after the 4th or 5th day of birth15. Eventually, when the young are first separated from their parents and put into an unfamiliar place, they may become nervous of their environment. Typically, they do not groom or play as normal at first and increase the amount of vocalisation, neck-nosing and forepaw clasping14. However, the degu's brave personality ensures the pups soon familiarise themselves and start exploring.

Degus experience delayed puberty, a feature uncommon amongst rodents68. Although there is wide variation in the age at which degus reach sexual maturity, female degus often mature sooner than males. Female pups will reach puberty around 7 weeks old31, whilst male pups reach puberty around 12 weeks of age31. It is safest to re-house the pups in same sex groups when they are weaned, around four to six weeks old68. The father must also be separated from the mother and all female pups at weaning, no later than 6 weeks. If necessary, the father can be housed with any male pups, while the female pups may remain with the mother.

>CONSIDERATIONS...<

Captive degus can in some cases breed throughout the year36, although it is safest for the female to have a maximum of two litters per year31, and ideally only one. It should also be brought to attention that captive degus have a very poor genetic history and extra special care should be taken to prevent inbreeding and congenital inheritance of problem conditions. Breeding is a process that takes time, care and attention and it is imperative to be sure you are fully committed before breeding degus.

PLEASE NOTE that females with cataracts can suffer a SUDDEN DEATH in late pregnancy if used to breed from36. For congenital reasons you should not breed from any degu with cataracts anyway50 (see health section). Other breeding problems associated with cataracts and diabetes in the degu include fertility problems36, females give birth to fewer pups36 and pup survival to weaning decreases36. JUST DON'T BREED FROM A DIABETIC DEGU!

Older male degus may become infertile, as senile male degus have been found to have a decreased sperm cell production ability39 and lower testosterone levels39. Older males will also become less able to produce healthy spermatozoa if there is no continuous production39. It is therefore a good idea to keep your breeding males in a continuous breeding program to allow maximum fertility. It's also a good idea to check your males are getting enough supplemental vitamin C in order to enhance reproductive function63. If your male is infertile and you already supplement his diet with vitamin C, check the dosage as excess can cause reproductive failure63.

Other considerations when preparing to breed degus include a 'responsible breeding checklist'. Listed below are the key points to consider before you decide to breed:

TIME- Do you have the time to devote to what can be a lengthy and time-consuming process? You should prepare for even the worst-case scenario of having to hand rear pups (which requires feeding times evey 2 hours around the clock for at least 2 weeks).

GENETICS- Do you know the health history of the degus you intend to breed? If you don't know the background of a degu, you can't be sure their parents were healthy or bred responsibly. Captive degus are the unfortunate victims of years of chronic inbreeding, so it is very important to be sure that degus used for breeding are passing on healthy genes and NOT common degu problems such as congenital cataracts and molar teeth problems. More information on this can be found on the breed standard section.

SPACE- You will need enough room and spare cages to breed degus responsibly. Remember that male degus need separating from the females for around 4 days immediately after she has given birth, and again once the pups are weaned. You'll also need room to segregate the male and female pups before they go to their new homes. Also it's advised to house male and female degus separately outside breeding season in order to prevent unexpected and unplanned pregnancies.

HEALTH- The health of your degus, in particular your female degus, should come before everything else. Pregnancy puts an incredible strain on the female's body, so if she's not in peak condition, it's not fair to put her through the extra stress. Remember that female degus should not be allowed to breed until they weigh over 220 g, and should not be bred from once they're over 5 years old when they're considered to be in old age. It's recommended female degus have no more than one litter per year in order to give their bodies plenty of time to recover.

INBREEDING- Because of the small genepool of captive degus, it's incredibly important to avoid inbreeding at all costs. This means you should be absolutely certain that the degus you intend to breed are not directly related, i.e. are not siblings, parent and offspring, grandparent and offspring or grandparent and grandchild. Direct inbreeding significantly increases the risk of infant mortality, congenital abnormalities and deformities, so PLEASE avoid it at all costs.

COST- Breeding degus is NOT a way to make easy money- if this is your only reason for considering doing so please stop! Breeding can be expensive and you need to MAKE SURE to set aside some money to cover unexpected costs, such as emergency vets bills. Things like an out-of-hours emergency c-section can cost well over £100, and not having the money to cover it IS NOT an acceptable reason to allow your degus to suffer.

HOMING PUPS- A very important consideration before you start is how you will find good homes for any pups that are born. Females have an average of 6 pups per litter, but can have almost double this number, which means a lot of good homes are needed. Of course, you should always home your pups in same sex pairs or more, unless the new owners are planning on integrating a single pup to another young degu. It can be quite difficult to find homes for degus, so it's a good idea to breed to a waiting list and find homes for pups before you start. It's also very important to make sure the new owners are responsible and will give the degus a good home, which includes giving them the right information about care to get them started. A good breeder will always be happy to be contacted by their customers for follow-up advice. Remember that it was YOU who brought the pups into the world, so it is YOUR RESPONSIBILITY to ensure they are looked after appropriately- it's only fair!

SEXING PUPS- Another key factor is making sure you're confident about how to sex degus, particularly degu pups. If you have gone to all the effort of outbreeding healthy, happy degus with sound genetics, the last thing you want to do is get the sexing wrong and send new owners off with mixed sex pups by mistake. It's not fair to put new owners through the trauma of having to cope with unexpected babies! Sexing degus, even newborn pups, is easy once you know how- see the sexing guide for advice.