Frogs (All About)
Frogs belong to the animal group amphibians. These are cold-blooded creatures that cannot control their own body temperature but are affected by environmental temperatures. Another distinguishing characteristic is that they are able to take in oxygen in two separate ways. They have lungs, which they fill with air which they inhale from the atmosphere. However, when they are hibernating at the bottom of ponds in winter, they are able to absorb enough oxygen from the water through their skins to keep them going.Read moreRead less
In February frogs wake from hibernation. Males hibernate at the bottom of ponds and females hibernate in separate quarters at the bottom of wet ditches around fields. These female frogs, upon wakening, hurry to the ponds where the males are encouraging their arrival with loud croaking. The females and males both enter the water where mating takes place. The male climbs on to the back of the female and holds her with his nuptial pad — a very well developed thumb. When she produces her eggs in a cloud into the water, he immediately squirts sperm all over them and fertilisation takes place in the water.
The fertilised eggs swell up and float in a jelly-like mass called frogspawn. The couple then disengages and they go their separate ways. Frogs spend the rest of the year in wet fields and meadows and in gardens feeding on flies which they catch with their long sticky tongues. They never go back to the pond until hibernation time in October when the males return. The eggs are left to fend for themselves.
Meanwhile back in the pond, the black eggs in the transparent jelly become larger until they finally hatch out into tadpoles. These are completely aquatic creatures, with gills on their long tails and they get all their oxygen requirements from the water through these gills. They are carnivorous creatures and indeed if they are short of food will even eat each other as many the owner of a tank of frogspawn will testify. Frogs are protected under European legislation because they are scarce in Europe in general.
However, they are not endangered in Ireland so a general licence has been issued to all Centres of Education in Ireland to collect and study frogspawn in class in tanks, etc., without individually having to apply for a licence to the National Parks and Wildlife Service. Tadpoles slowly develop into small frogs, growing first their legs and then finally losing their tails. If they are kept in a tank the water must be changed regularly as a build-up of enzymes from the tadpoles prevents them from developing into frogs. They can be fed with fish food — daphnia — which is sold for goldfish. When they have all four legs and lose their tails, they will leave their watery environment and hop around grassy meadows catching food for themselves. In turn, they are food for birds such as herons.
Things to do
1. Note the date when first frogspawn is seen, to build up a series of records over the years.
2. Bring in frogspawn to class (or into the school pond) and observe the stages of growth. Release the frogs back to the wild when fully grown.