Mean fertility in three koala populations in Victoria in 1979 varied from 63% on French I, to 13% at Walkerville and 22% on Phillip I. Similar differences between the two island populations have existed for at least 30 y. A method of assigning animals to age classes on the basis of the wear patterns on the premolar was devised and reproduction in 1979 examined on an age-specific basis. The low fertility was associated with a reproductive failure among females older than 3 y. On Phillip I. this is thought to be due to a widespread reproductive tract disease in females, possibly caused by ingestion of phytooestrogens from eucalypt foliage. At Walkerville a combination of reproductive tract disease, poor nutrition and heavy tick burdens is thought to be the cause.
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RW Martin (1981) studied this question.