Just how do frogs mate? And when do females release their spawn? We explain...
What is spawn?
Spawn means release of eggs
When does spawning take place?
Frogspawn has always been one of the earliest and most eagerly anticipated signs of spring, but with a trend for milder winters you may spot it earlier than ever. Late January and early February records are certainly not uncommon.
“Usually, spawning begins in the south-west, then advances across the country in a north-westerly direction, moving around frost pockets,” says John Buckley of the Amphibian and Reptile Conservation Trust. “Day length and air temperature fire the starting gun. Keep an eye on your thermometer for when it hits 5°C.”
Frogs can breed in colder conditions than toads, which mate from March onwards when the temperature reaches 7°C; also unlike toads, frogs hibernate in or near their breeding ponds, so there is no need to migrate there first. There are obvious advantages to starting the breeding season early, but frogs can only spawn once each year – any spawn lost to freezing weather is not replaced.
How do frogs mate?
In most species of frog the male frog fertilises the egg outside as the female lays them.
To do this males need to attract the females to them, and do so by croaking. If successful the male grips his mate tightly in a hold called amplexus, using a soft swelling on the inner finger of each front foot, known as the nuptial pad, to cling on. The male uses his rear legs to kick rivals away, instead of gripping the female. Spawning mostly occurs at night and is rapid, lasting seconds.
How long does it take for frogspawn to hatch?
Freshly laid spawn is all-dark, rather like caviar, but soon takes on water, developing into the familiar clear jelly with black centres. If healthy, spawn takes 8–10 days to hatch.
However during cold snaps, frosting may kill spawn at or just below the water surface, turning it white. The risk is greater in shallow water, so make part of your pond 15cm deep to reduce the chance of this happening.
Main image: Breeding frogs © Ingrid Cawse