Wildlife in the Strath by Ray Collier

Frogs have various shades and patterns of green, yellow or brown and an easy way to identify any of the adults or well grown young is the dark patch behind the eye. They move in short, sometimes long leaps unlike the toad that crawls. Frogs have a smooth, moist skin whereas the skin of the toad is rough, normally dry out of the water and warty.
The single croaks of the toad contrasts with the churnng croaks of the frog. Frogs are much more widespread in the strath as they are more catholic in their taste of breeding sites. Toads tend to breed in deeper water such as Loch Farr and the Little Mills loch on the Esker Trails. Toads always leave the water after the breeding season and hibernate in roughly the same area.
Frogs can stay in the water over winter as, unlike the toad, they can absorb oxygen through the skin. Frogs will leave the water if it gets very cold and freezes and then they will find holes in the ground scattered around their breeding site. The eggs of the frog are laid in batches that eventually float, unlike the toad’s eggs that are laid in narrow strips that are wound around submerged aquatic plants. The main problem that frogs have is that they have the tendency to deposit their clumps of spawn in any area of water and if there is rain as the frogs lay they will even lay in water filled tractor or cart tracks which in many cases soon dry up and eggs and/or tadpoles die.
You can estimate the populations of adult frogs as each female lays one batch, albeit of 1,000 to 3,000 eggs. Mortality of~ tadpoles is very high from fish, birds and mammals and adult frogs have more predators than toads as they lack the poisonous secretion of the toad’s skin. Once the frogs eggs have been laid, normally low in the water, the jelly coating swells and the clumps float to the surface, often in huge batches where several females have laid together.
The new tadpoles have external gills but these are absorbed and the hind limbs form at seven weeks and once the fore limbs are formed the tail is absorbed and then the froglet leaves the water to face yet more predators.
If you want to have frogs in your garden pond it is best not to have any fish as they will eat the eggs or tadpoles. There is nothing wrong in transferring spawn into your garden pond if the frogs breeding site is threatened. We are lucky in the Highlands that we still have many water bodies such as lochs and lochans that support large numbers of frogs. In southern Britain there is such a shortage of natural sites that in many large areas the only frog colonies are in garden ponds.