NO big surprise here, but still interesting. The difference between 4
and 29 species is huge, but maybe just an effect of having running and
still water with more sunshine???
*Beavers great for dragonflies and damselflies!
//News / 27th October 201/2
The effect of the Eurasian Beaver on Dragonflies and Damselflies (Odonat*a)
by Sara Schloemer, Lutz Dalbeck and Andreé Hamm. Institute of crop
Science and Resource Conservation (INRES)*.
As a result of a reintroduction project in 1981 the Eurasian Beaver
returned to the Hürtgenwald, a large woodland area in the Eifel mountain
range in the extreme west of Germany. The study looked at the effects of
the large-scale changes to dragonfly and damselfly communities in the
narrow, originally wooded, mountain valleys of the northern Eifel are*a.
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
3. Beaver ponds (some 10 -15 years old, up to 2000 m², sunny to
4. Beaver ponds abandoned for 1 to 3 years.
All areas were searched for dragonflies and damselflies, their larvae
and exuvia throughout the season in 2011 and 2012.
In addition chemical and physical parameters such as pH-value,
temperature, and water speed were measured at all sample sites, and
makrozoobenthos collected, in order to gather information on the water
quality in both the presence and absence of the be*aver.
With a total of 29 species, the number of species in beaver ponds is
markedly higher than in ponds without beavers (4 species). Even in
abandoned beaver ponds the number of species is higher than in the
streams (7 species).
If species typical of the streams are considered, these also profited
from the influence of the beaver. This is due on the one hand to the
dams, which are clearly very suitable habitat and on the other to the
increased exposure to sunlight, even on stretches of running water,
caused by the beaver's acti*vities.
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
- 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
List of Dragonflies and Damselflies associated with beaver modifi*ed
habitat (the usual habitat these species are found within is shown
Still waters, small, sunn/y and bare
Still waters with well developed/vegetation
Standing waters, w/ell-vegetated
Standing and slow-/flowing water/s
Preferring small a/nd shaded pon/ds
Acidic heath/y lakes and /bogs
Still and s/lowflowing waters
mainly runn/els in boggy areas
Small streams, preferring scant/ily vegetated sites
Streams, in forests, o/pen moors and heath/s
All kinds of slow-flowin/g and standing water/s
Pioneer /of newly create/d ponds
Mostly acidic waters, bogs, mo/orland and heathy lak/es
Acidic, oligotrophic lakes, tarns and bogs, also r/ichly vegetated habitat/s
Less acidic, mesotrophic bogs, forest lakes, /marshy ditches and/ oxbows
Ree/dy canals, marshes, /oxbows
Run/ning waters, avo/iding shade
Running water, cl/assic habitat for/est streams
Running and standing water, favours the p/resence of aquat/ic vegetation
Running /and especially st/anding waters
Small or tempo/rary ponds
Running and still water
Any standing water, numerous /at recent sha/llow or acidic sites
/Heath and bog/ lakes with peatmoss
Standing or slow flowing wa/ter with bordering t/rees and bushes
Small streams,/bogs and heathy la/kes with peatmoss
Well-vegetated standing and running waters
California Dragonflies www.sonic.net/dragonfly
Southwest Dragonflies www.southwestdragonflies.net/
Bigsnest Wildlife Pond www.bigsnestpond.net/
Kathy and Dave Biggs bigsnest@...
308 Bloomfield Rd. Sebastopol, CA 95472
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