It usually takes both males and females in order to reproduce successfully. However, a team of scientists from the Institute of Animal Physiology and Genetics CAS and the University of Ostrava found out that the entire population of edible frogs in the Oder River basin is made up of males only. Such populations of other four-legged vertebrates are not yet known of anywhere else in the world. They “steal” the eggs from the marsh frogs. At the turn of April and May, the still areas of water come alive with frog choruses and thus, this intriguing reproduction process can be observed again after a year.