Peter, it does sound as though your Frog succumbed to red-leg disease, although it is supposed to be more prevalent in late summer and autumn than in winter. However, around ten years the thriving population of frogs in my garden pond was decimated by what appeared to be this disease and I found no less than 19 of them dead in February/March, soon after they emerged from hibernation. All showed the signs you describe, namely, inflamed looking patches of red or pink, especially on the legs, and split skin. Since then I have had very few frogs in the pond and none this year. As you have only found one it could be that this was an animal weakened by long months of hibernation and thus particularly vulnerable to this type of bacterial infection. There are several good websites that can provide more detailed information - Graham
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The weblog below is for naturalists to use to report interesting sightings, ask questions, report on field meetings and generally post pictures and any information or questions generally relevant in some way to the wildlife and geology of Essex. You will need to register and be logged-on to post to the forum, and you need to upload pictures first, for use in posts. Find out more