The island is most famous for its Campbell teal, which was thought to have been extinct for more than 100 years until a small group was rediscovered there in 1975. Dent Island is free from predators, especially the rats whose introduction on Campbell Island led to the extinction of the teal there. However, the suitable habitat for the teal on Dent Island is much more limited than its 26-hectare (64-acre) area would suggest, because a large area of the island is bare rock.
The Campbell teal conservation programme started in 1984 when four birds were transferred from Dent Island to the Pukaha / Mount Bruce National Wildlife Centre.[3][4][5][6] In 1997, a census carried out on Dent Island showed that its Campbell teal population had declined to dangerous levels with only three birds being found.
However, the conservation and breeding has been very successful, and in recent years many teals have been reintroduced onto Campbell Island itself, where there is now a population of over a hundred. Rats were eventually eradicated from Campbell Island in 2001.