But more than anything else, the species owes its spread to a strange phenomenon discovered in 1930 by the biologist Lancelot Hogben. Heavens knows what led him to do it, but Hogben found that if you injected an African clawed frog with the urine of a pregnant woman, within hours it would lay eggs. Before chemical pregnancy test kits became available in the 1960s, African clawed frogs were kept in labs and hospitals worldwide for confirming pregnancies. Many escaped, or were released, including the founders of a population that became established in South Wales.