The Natterjack is the much rarer relative of the Common toad and is usually only seen at its key hotspots. It is slightly smaller than its cousin and greenish-brown in colour, with a very distinctive yellowish stripe running all the way down its back. Present in both the male and female, this is easily the best way of identifying the species. Like the Common toad, its skin is warty and rough. The eyes are greenish-yellow, rather than copper-coloured, and it has shorter legs, giving it a slightly stockier appearance. Female Natterjacks are generally larger than their mates, but perhaps the biggest difference between these two species is their sound: whereas Common toads croak quietly, male Natterjacks churr loudly in a chorus that can be heard several hundred yards away, using the large sac on their throat to amplify the sound. Unlike the very widespread Common toad, the Natterjack is found at fewer than 100 sites scattered around the country, and almost all along the coast: this species prefers the drier soils of heathland as well as salt marsh and sand dunes. Strongholds for the species include Formby Dunes, on Merseyside, and parts of Cumbria, Lincolnshire and North Norfolk. The Natterjack has now also been reintroduced to other sites in southern Britain, in an effort to extend its UK range.