Brought to our attention by our beaver friends in Wales but based on a study conducted in Germany
The effect of the Eurasian Beaver on Dragonflies and Damselflies (Odonata)
In order to compare beaver ponds with woodland streams representative of large areas north of the Alps, but yet not influenced by the beaver, we studied the following habitat types:
1. Natural springs (definite woodland springs)2. Streams (natural – semi-natural in woodland, not influenced by the beaver)
3. Beaver ponds (some 10 -15 years old, up to 2000 m², sunny to half-shaded).
4. Beaver ponds abandoned for 1 to 3 years.
Now, being as that I’ve been watching our own beaver ponds for the last 5 years and have seen the density of dragonflies wholly influsenced by the quality and quantity of dams, I’m going to guess the answer to this research question before I get to the end of the story. The year that our dams and lodge were totalled, and mom was dead and dad took off for a while, there was a huge drop in our summer aviators – partly because everything they wanted to eat was washed away. But let’s see what they found anyway? (And by the way, if you’re like me you would appreciate a reminder of the difference between dragonflies and damselflies) when at rest damselfly wings lay parallel to the body, while dragonflies are still perpendicular like airplanes. Now with that out of the way, lets read on:
Conclusion
Despite the relatively short period of time since the return of the beaver, and the rather small number of beaver ponds, the ponds already now make a remarkable contribution to the conservation and spread of rare dragonfly and damselfly species.
Beavers contribute markedly to nature and species conservation in the densely settled countryside of Central Europe. The species should therefore be more greatly integrated into plans to implement conservation measures and renaturisation of water bodies than it has been to date.
Particularly notable are:
– The extraordinary combinations of species (boreal alongside sub-Mediterranean species)– The extremely different habitat requirements of the species
– The increase in typical stream dragonflies and damselflies in spite of damming by the beaver
– The increase in part of highly endangered species
Are you shocked? Me neither! Being that dragonflies eat the kinds of things that hatch in beaver ponds, it should be a surprise to no one that they actually do better with some beavers around to make and maintain the ponds. Still, we are always grateful when someone goes to the trouble of documenting the obvious, because it is apparently very hard for some people to see even with proof.
A dragonfly is a remarkable predator. Once I sat in the sun and a slender blue example decided to sit on my knee, and use that perch as a landing pad for his continued predation. He would wait with little twitches of his tale, discoball eyes on the gnats floating around my garden, spy one that looked a likely target and ZOOM zap out of his perch to snap the gnat up mid-flight and then settle again on my knee perch while he was still swallowing. He would repeat this as long and as often as I watched or waited. I remember once a million years ago rescuing a drowning dragonfly in my canoe off mirror lake in Lassen, and allowing its drenched form to dry in the sun while I paddled about. While the soaking creature dried at close range I was very surprised to learn that even though dragonflies have pretty remarkable wings, when you are in any proximity to them you realize fairly quickly that are also really big carnivorous bugs.
So there are more kinds of dragonflies and damsel flies at beaver ponds? Gee, I guess there must be things that eat these creatures too! Someone should do a study on whether their populations go up near a beaver pond next!
