Original: A twelve-year field study, published in 2003, found that the Short-beaked Echidna reaches sexual maturity between five and twelve years of age, and that the frequency of reproduction varies from once every two years to once every six years.
Simplified: A twelve-year field study, published in 2003, found that the Short-beaked Echidna reached sexual maturity between five and 12 years of age, and that the frequency of reproduction varies from once every two years to once every six years.