Though not thought to be native the frog is now a very common and widespread amphibian, being found from the most low-lying to the highest places, wherever there are freshwater ponds. The remarkable life cycle of the frog begins in late winter when masses of them congregate in ponds, ditches and the like having overwintered in hibernation. Here nuptials and mating occur en masse, the smaller males sitting 'piggy back' on the females and fertilising the eggs as they are laid. The spring-time metamorphosis of spawn to tadpole to froglet to frog is a spectacle that has instilled wonderment in count less generations of children and forms the centre-piece of many a school nature table. Frog food is mainly small and invertebrate like snails, slugs and insects. Frogs vary considerably in colour from yellow brown to green and even grey and are capable of changing their colour to suit their environment.