Thursday, 5 April 2018

Specieswatch: spring ice has made life hard for the common frog

Many common frogs were trapped under ice in early March and some inevitably died

Tue 27 Mar 2018 21.30 BSTLast modified on Tue 27 Mar 2018 22.00 BST

The common frog Rana temporaria is having a difficult spring. The extreme cold at the beginning of March trapped many under ice. A lot continued to breathe through their skin, but after several days some died from lack of oxygen. The survivors then got breeding under way in many ponds, only for another three-day cold snap to halt proceedings. Some ponds still have no spawn, while in others the adults have already left piles of jelly to take their chance.

After years of observation – at least in parts of central England – it appears frogs that breed in shallow ponds that often dry out in the summer are the first to lay their eggs. The tadpoles have the advantage that there are few predators in a seasonal pond, but to survive they may have to develop extremely quickly if the spring and early summer are unduly dry. It seems hardly credible that the adults sense this and breed early, but in many deeper ponds that are never allowed to dry out, particularly in gardens, the frogs habitually mate later. Both breeding strategies seem to work, but which is most successful is hard to tell. Perhaps it varies each year depending on the weather.

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