Nature notes – by Dave Moore, wildlife enthusiast from Hutton Magna
HOW many readers collected frog or toad spawn as a youngster? Thousands of classrooms had an aquarium with “Taddies,” and their development was observed with great interest. Nowadays, finding a breeding pond is difficult as many have disappeared. Bearing this in mind, the practice should not be encouraged today.
When frogs and toads get to their ponds, the business of breeding really commences, although frogs arriving early sometimes have quite a long wait and all they seem to do is sit around on the pond bottom.
This has been described as the “pre-spawning period” and it can last several weeks as their numbers build up. Any females arriving are quickly grabbed by males who then become passengers and have to go everywhere the female decides to swim. The females that have arrived early, or have hibernated in the pond, run the risk of being grabbed by more than one male and held in a tight embrace for several weeks. This quite often results in wounding or even death by drowning of the unfortunate female on the receiving end of such passion and ardour. To my knowledge nobody knows what triggers the frogs to start spawning, but after dark they all move into shallow water, a few centimetres deep as a rule, all together in one part of the pond. The males have subdued croaks, this is the noisiest time of the year for all amphibians, but the common frog is not an impressive performer compared with other species; what they lack in voice they do make up for in determination. Lots of fighting takes place with rival males trying to force off others already paired up with females.
Frogs egg laying is mainly done in the depths of the night and the spawn is ejected in a single mass in a matter of seconds. Fertilisation is external and the male has to be quick off the mark shedding his sperm precisely as the eggs are laid.
The spawn quickly swells in the water, and after only a few minutes the eggs are no longer accessible to sperms, and will therefore not be fertilised. The male releases the now skinny looking female, who then swims away from the colony to hide in a quiet corner of the pond. If frog breeding sounds a frenzied affair, that of the common toad is more so.
No “pre-spawning” period here, but a mass “splash down” into the pond, a rapid burst of spawning takes place which goes on night and day without a break unless the weather turns cold, whereas frogs usually spawn in the early hours, also toads prefer deeper water than frogs – up to a foot deep although they embrace the same as frogs. The eggs are laid as long strings rather than squat clumps.
This leads to their behaviour being different too, because a string of eggs cannot be shot out all at one go. What happens is that he feels with his toes when the eggs start to emerge, and sheds his sperm over them until the female stops for a rest. The whole business takes several hours, with bursts of spawning interrupted by 15 minute breaks. During this time the pair are anchored by the spawn string which is usually wound around water plants some two to three yards long.
The migration of toads to their breeding ponds, usually takes place during the latter part of March and the beginning of April locally. The Stang is a main breeding area. The first time I came across a breeding pond there, I discovered it by the noise from the humming males.
At a fair distance it sounded like a large flight of second war planes passing. The particular pond contained hundreds for the amount of noise being made. There are still plenty of toads breeding there, but not in the same numbers.
I’m sure many readers will have come across toad flattened on roads and country lanes. Next time pick a few that are alive and release them in your garden, they just love consuming slugs. I don’t have a slug problem in my garden.