Chumbe's Successful Rat Eradication Program

Rat infestation is a common problem on islands worldwide. On Chumbe, Rattus rattus was a serious pest, probably introduced when the lighthouse was established on the island around the turn of the century. Part of the breeding colony of Roseate Terns Sterna dougalli was decimated by rats in 1994, and the birds did not come back to breed on Chumbe probably for this reason. Any bottom-breeding bird species on the island are threatened by rats. In addition, rats are a serious health hazard, damage buildings, electrical cables, diving gear and food-stuff and are a menace to rangers and visitors alike, thus frustrating prospects for Eco-tourism.

Measures to control or even eliminate the pest had been considered since 1994, in consultation with experts from New Zealand, Germany, Netherlands, Britain and Ireland. One very interesting option considered was the biological control of the pest by introducing a rat-specific pathogen, the monocell Sarcocystis singaporensis from Thailand. This could not be pursued further, as Tanzania lacks the legal framework for introducing exotic species for pest control. A SES-consultant visited the island in early 1996 and proposed a more conventional control strategy with rodenticide.

Finally, in April/May 1997, an Irish scientist funded by the Agency for Personal Services Overseas (APSO), Dublin, has succeeded in eradicating rats on Chumbe, by using a second generation rodenticide donated by the British firm ZENECA (former ICI). The rat campaign has been conducted with close monitoring of any possible effects on non-target species. Monitoring of any reappearance of rodents continued until August 1997, including measures to prevent re-infestation. A scientific publication on the methods used and results of the campaign is being prepared. It is probable that the expertise gained during this campaign can be deployed in other rat infested islands in the region.

The rat eradication campaign on Chumbe was conducted in close co-operation with the Plant Protection Division of the Ministry of Agriculture, Livestock and Natural Resources, the EDG-Zanzibar Project and CHICOP.