Female alpacas are usually ready to mate between 12-18 months of age. This is variable of course as some alpacas mature earlier than others, but weight is always a good indicator of whether a young maiden alpaca is ready and usually this is over 40kgs.
Often the behaviour of the young female will tell you when they are mature. If there is mating going on nearby and your young alpaca girl sits down, that is a sure sign she is looking for a mate.
Once the female has been mated she is usually introduced to the male again after a week and at various intervals and if she spits at him and refuses to sit again it is likely she is pregnant.
Ultrasound tests are often done after 60 days to confirm the pregnancy. Gestation is usually between 11 and 12 months depending on the time of year - spring births are usually later than autumn births.
Birthing is usually in the morning and the new baby alpaca (cria) is usually up and running quite quickly as alpacas are predated animals and instinctively know that if they cant keep up with the herd they will end up as another animals breakfast.
The placenta arrives soon after and needs to be taken away as unlike some animals, alpacas don't eat it.
Although it is always good to be on hand, alpacas usually cope on their own and other than a quick check to make sure the cria is ok and a spray of iodine on the umbilicus, mother and baby alpaca are best left to bond. Observe from a distance if the cria is feeding. We usually leave it until the end of the day to weigh them. When you hear the mother making a "nuk, nuk" sound and kissing the cria, then bonding has begun. The booklet Antenatal Birthing and Cria Care for Alpaca Owners by McMillan and Jinks is a wonderful reference book on before, during and after a birth. (pictures of Silva giving birth and with cria)