They are grilled and eaten in some countries, but in Berlin crayfish have been scuttling across streets and pathways in and around Tiergarten park. Originally from North America, red swamp crayfish that grow up to 15 centimetres long have been creating quite a fuss amongst passersby in the capital. "We’ve been receiving telephone calls almost daily from people who report sightings of the migratory animals," Ulrike Kielhorn, an expert at the Nature and Biodiversity Conservation Union (NABU) said last week. The calls have been in regards to a species of American freshwater crayfish known as Louisiana crayfish. The crustaceans have...