Having batrachians in your garden could quickly lead to complaints from your neighbours, as they tend to make quite a racket ! Their presence in a town garden is particularly unadvised !!
As frogs, toads, tritons and salamanders are protected species, it is strictly forbidden to collect their eggs or to capture adults in the wild. It is also illegal to introduce exotic species, sold in pet shops, into your garden.
In any case, adult frogs tend to return to their place of birth to reproduce and lay eggs. If you wish to have frogs in the garden, you just have to wait until they come themselves. They require a particular biotope, such as the presence of a second source of water to migrate to, and a pond with plenty of sunlight, rich in insects. If you have these installations, they will come themselves. In winter, they bury themselves beneath the mud to hibernate, so you require a pond at least 60 cms. deep with a good layer of mud at the bottom. This is suficient for their hibernation, except if the winter is extremely cold.
You may also find that tritons, salamanders and toads come to colonize your pond. Again, don’t install them yourself, as they will not stay.
Cats love to hunt batracians, so install the necessary protection around the pond, otherwise straying cats wil have a feast !