How common is a common dragonfly?

Female Broad-bodied Chaser

My Oxford colleague Liz Mitchell has just sent me this nice photograph of a recently emerged female Broad-bodied Chaser which emerged from her 1 year old garden pond a few days ago.

The picture prompted a few thoughts about this supposedly common dragonfly.

The Broad-bodied Chaser is usually described as common and widespread: so it’s  easy to think you’d find it in pretty much every pond you looked at, at least inside it’s range. But the evidence suggests it may not be quite as common as this picture implies.

The distribution of the Broad-bodied Chaser: each dot shows the presence of the animal in a 10 x 10 km square of the national grid

In the best conditions – pollution-free, high quality ponds – it should be found in about 1 in 10 ponds. This is how often we found it in the National Pond Survey – our study of what lives in ponds when they’re in good condition. So even where ponds are in good condition, it’s not really all that frequent.

But sadly out in the real world, most ponds are not in good condition: in fact 80% are in poor condition.

And in the ‘typical’ (degraded) ponds of the British countryside, Broad-bodied Chasers turn up in only 3% of ponds – that is, 1 in every 30 ponds.

With a range covering half of Great Britain, where there are roughly 250,000 ponds, this means that this animal probably is found in maybe 7,500 ponds – say 10,000 to be generous.

So this suggests it’s nothing like as widespread as a simple glance at the map might lead one to expect. (Just by way of contrast the Southern Hawker dragonfly is found in about a quarter of all ponds – so perhaps 65-70,000 ponds altogether).

So is the Broad-bodied Chaser under any kind of threat? Well – at the moment, probably not. It’s a good disperser, it colonises new ponds – like Liz’s – and it’s spreading north.

But is it as common as it should be? Equally certainly – no. If ponds were in better shape generally we might expect to see it in 25,000-30,000 ponds.

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One Response to “How common is a common dragonfly?”

  1. Dean Fenton Says:

    Hi,

    we have a largish pond in a field on our Herefordshire smallholding. We created it 5 years ago and for four years Broad-Bodied chasers were present and bred in the pond. This year I have only seen 4 Spotted chasers there (three or four have been present). Would these displace the B-B chasers after the latter emerge?

    I did not see 4 Spotted last year, so do not know whether they bred at the pond, but I think not.

    Dean Fenton

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