Understand frog breeding behaviour

Early spring is a busy time in the pond - it's time for frogs to find a mate.

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Breeding frogs © Ingrid Cawse

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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.

Four fascinating facts about frog breeding:

1. 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.

2. Females are marginally larger (the disparity is more significant in common toads, where females may be twice as big as their partner). Frogs live up to five or six years, and keep growing: a big frog is an old frog.

3. 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.

4. 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.

And did you know?

Frogs may be reddish or have very dark markings. Genes and water chemistry affect coloration, so there’s a regional bias to some forms; individuals can also vary skin tone to an extent to blend in.

Groups of males croak on damp nights – a soft sound like distant motorbikes. Lone males seldom call. Marsh frogs, a non-native species found in the south-east, are far noisier and call by day or night.

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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.