Brutal Peruvian slave traders, known as blackbirders, took a terrible toll on the islands of the Northern Group in 1862 and 1863. At first the traders may have genuinely operated as labour recruiters, but they quickly turned to subterfuge and outright kidnapping to round up their human cargo. The Cook Islands was not the only island group visited by the traders, but Penrhyn Atoll was their first port of call and it has been estimated that three-quarters of the population was taken to Callao, Peru.[9] Rakahanga and Pukapuka also suffered tremendous losses.[10]