Frogs

Frogs and toads have come under a number of threats in recent years. Many of their usual breeding places are disappearing, as ponds become filled in or polluted because of housing development or intensive agriculture. Large numbers are dying on the roads, especially toads on the way to their breeding sites. Over-collecting of spawn may be another factor on the decline of frog and toad populations.

Breeding
Frog spawn is laid in clumps in shallow water, while toad spawn forms long strands winding around aquatic vegetation in deeper water. It takes about three weeks for tadpoles to emerge, and a further 12 weeks before they become mature froglets (6 - 8 weeks for toadlets).

Keeping Frog and Toad Spawn in Captivity
Spawn should only be collected from garden ponds that are really overcrowded with it - and it is important to take only a very small amount. One clump of spawn might produce 200 tadpoles, and in a confined space most would die of starvation or an oxygen shortage. Tadpoles kept in overcrowded conditions eventually begin to eat one another. Spawn should NEVER be taken from the wild.

The spawn or tadpoles should be put into a small aquarium tank filled with rain or pond water. Tap water should be avoided if possible, as it can kill tadpoles. If it has to be used, it should be allowed to stand for several days beforehand. The water should be changed whenever it becomes cloudy or dirty.

Tadpoles will eat canned spinach (washed to remove the brine), bits of boiled lettuce, or food pellets sold in pet shops for rabbits or hamsters. For 100 tadpoles about 5 large pellets should be given every 3-4 days. As soon as the hind legs begin to appear, the tadpoles must be given small pieces of red meat - but be sure to remove any pieces of uneaten food before it begins to rot. The best time to release the froglets is when the hind legs are large, but before the front legs start to appear. If kept any longer, the froglets might escape from the container or drown. Newly metamorphosed frogs are fragile, and drown very easily.

Froglets should be released in shallow water at the site from which the spawn was taken. If they are to be introduced to a new site, it must be one that does not dry out in summer, and does not have strong currents or fast moving water. It should have shallow areas for spawning, and some plant life, and it should not contain a high density of predators such as fish, newts, ducks or moorhens - although common newts will usually leave toad tadpoles alone. If the proposed site is part of a nature reserve, it is essential to consult the conservation body responsible for its management before introducing tadpoles (or any animals or plants), otherwise the delicate ecological balance may be upset.

Hibernation
Frogs hibernate at the bottom of ponds, under old logs, in stone walls or in compost heaps. Toads hibernate on land under stones or logs, or in a hole in the ground. They rarely hibernate in water. In a severe winter frogs may die if the pond remains frozen for a long time: toxic gases such as methane builds up from decaying vegetation, and cannot escape because of the ice. To prevent this, melt the ice from time to time by standing a saucepan of hot water on it.

Interesting Facts
Garden ponds are becoming an increasingly important refuge for frogs forced out of their old habitats. It has been estimated that nearly 50% of frogs in Britain live in garden ponds. This can be good news for the gardener, as they eat a number of insect pests.

Frog colonies tend to be fairly small, so they can exist quite easily in gardens, but toads in field ponds frequently form colonies of over a thousand. Frogs and toads usually return to the same pond every year. If the pond is small it may become overcrowded, in which case spawn can be transferred to a neighbours pond or to a suitable site in the wild, preferably where spawn is already present (see keeping frog and toad spawn above).

For further in formation about frogs and toads contact Nottinghamshire Wildlife Trust or Dr. Sheila Wright, Natural History Museum, Wollaton Hall, Nottingham.