Frog Spawn

My favourite sign of spring - frog spawn - arrived on 23 February. Hurrah! More kept turning up, mostly during the night it seemed. In one of my day time visits I managed to capture on camera an amorous pair. The others dived promptly before I arrived.

Was the male’s eye injury the result of a bite from a cat or a fox? Both attack the frogs, but do not eat them. See this video.

In the end we had loads of spawn and no frog casualties. Good reports from some neighbouring ponds too. This is extremely satisfying because the local frog population seems to be on the rebound. They seem to have created some immunity against a devastating fungal disease: Chytridiomycosis or “chytrid”. At the same time, the local newt population is having an ascendent over the frogs, but more of that later.

Spawn has a low survival rate, apparently only 1 in 50 survive to adulthood, it has to contend with a lot of adversity. To start with, in our pond some of the spawn, which was laid in a very shallow area, hasn’t survived being frozen several times: the eggs have turned white.

Fortunately, the rest of it seems to be developing well and soon there will be plenty of tadpoles which brings me to the newts - their number one predator.

Newts 

In a good pond environment, frog tadpoles will be food for newts, damsel fly larvae, aquatic beetles, etc. But by far their top predator seems to be the smooth newt. During the breeding season lots of them turn up when pond dipping - to the delight of children.

Newts are very voracious carnivores and in the past they almost wiped out the frogs in our pond. Their reproductive season coincides with the frogs. Their eggs are pale cream, about 2 mm wide, very easy to spot in the aquatic plants. (In our pond we have hornwort, a native oxygenating plant - it is essential for good water quality.)

The female attaches them singly to submerged vegetation with her hind legs. A feat of dexterity. Plenty of eggs around now already. Their larvae look like miniature dragons and are very voracious.

Tadpoles vs newts

There seems to be a fine predator-prey balance between newts and tadpoles. Around here the present situation is that the newts seem to be winning: frogs have vanished from quite a few ponds. I confess that I have tinkered with this balance by rearing some tadpoles aside, then putting them back when they aren’t such an easy prey to the newts. After several seasons, it seems to be working.

The point is, we need plenty of frogs around to control the slugs and the snails and this brings me to ponds in the Drury Road Allotment Site. There are several ponds in the site, but there seemed to be no spawn in any of them last time I checked.

So what I’m suggesting here is that the site pond owners get together with others that have frog spawn to spare from their garden ponds and “seed” them with some tadpoles. It is a long term project, frogs need about 4 years to reach maturity, but well worth a try.

Good luck!

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Maria Fremlin, 19 March 2024.