Video cameras have recorded groups of up to nine mice eating the chicks alive. As a result of their success, the mice have become 'super-sized'. They are about 50% larger than a regular domestic mouse.
Many of the seabirds on Gough are small and nest in burrows. The chicks are smaller and have no escape route, so for an opportunistic mouse these chicks constitute relatively easy prey. The mice have done so well that they've grown bigger and are now attacking all seabirds, even endangered Tristan albatross chicks, which are far bigger than other, smaller sea-going birds.
Watch the documentary 'Tristan da Cunha – the Monster Mice of Gough Island' here.
Recently, a plan has been hatched to completely eradicate the mice. The operation is due to start in 2020. A ship will carry two helicopters and a load of poisonous, cereal pellets. These will then be spread across the island by the helicopters. They contain an anticoagulant which should kill the mice within 24 hours. They hope.
The Gough Island Giant Mice is an example of how quickly a species can adapt and become an example of island gigantism.