The Golden-headed Lion Tamarin is the introduced species. They were originally released accidentally (by a private collector) around the start of the 2000s in forest at Niteroi, which is within the historical range of the Golden Lion Tamarin. At the time of the first proper study (in 2009) there were already 107 individuals recorded, in 15 groups.Exactly how are Golden Lion Tamarins invasive within their native range? Surely witch such an endangered species, having them in their original range can only be a good thing?