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Stag beetles and magpies

Do stag beetles have any predators?
The answer is yes, of course, they are very much part of the food-chain. Magpies, blue jays, woodpeckers, owls, cats, foxes, bats, hedgehogs, badgers, wild boars, grey squirrels, and even frogs and toads seem to think that they are well worth a try.

In England stag beetles have fallen prey to magpies who hang around in gardens, waiting for the beetles to emerge, and then have a real feast. See below an example, 31 males and 12 females.

31 male and 12 female stag beetles

43 stag beetles killed by magpies. Photo by Maria Fremlin.
Colchester, Essex, England. June 21 2006.

Unfortunately photos like this one aren't rare, moreover they always show a very high male-to-female ratio, thus suggesting that magpies tend to do this right at the beginning of the season, catching them just as they emerge, consequently most of these victims probably hadn't had a chance to mate.
This poses many questions:
For how long has it been going on? For how long will it go on?
In other words, is this a sustainable situation for the stag beetle population?
Due not only to the great variability of stag beetle populations but as well to the fact that there is no data for the total number of beetles emerged in gardens where this happens, the above questions are unanswerable.
However it would perhaps help if the emergence sites where kind of camouflaged with some climbing plants, which would perhaps afford some protection for the emerging beetles. Also it would be nice if the person/s who live in such places took notes every year of the total catches, then perhaps a pattern could emerge. Just a thought!

PS: the answer to the last two questions seems to depend on the availablity of the wood. So long there is plenty of it, the females will carry on laying their eggs there. See this study:
Fremlin M., Davidson, J. & Davidson, G. (2012)  Stag Beetle Predation by Magpies in a Colchester Garden. Nature in North-East Essex, 2012, 81-85. [PDF]

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