Ultrasound technology and hormone assays have provided a better understanding of folliculogenesis and ovulation in South American camelids in the last two decades. Females exhibit waves of ovarian follicular growth and are induced ovulators and therefore do not exhibit oestrous cycles in the manner of spontaneously ovulating species such as sheep and cattle. There is much variation in inter-wave interval among camelid species (alpaca/llama 10-22 days, vicuna 4-11 days), within species and within individual animals as the range of each phase of follicular growth is wide. Ovulation occurs 24-30 h after mating and luteolysis occurs approximately 10 days later if conception fails to occur. (C) 2010 Elsevier B.V. All rights reserved.