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Moving Water Habitats
Many odonates inhabit moving waters. Moving water habitats include rivers,
streams, and seeps. Since some odes prefer rapid water, and others slow
moving waters, we have separated the two.
Rivers are larger than streams and can be defined as any body of water flowing
in one direction, usually emptying into a lake or ocean. When a rushing river reaches
a flat expanse, it undergoes a dramatic change. The waters spread out and
slow down, depositing their load of silt and creating a soft, muddy bottom.
In many cases the river becomes a series of meanders and oxbows.
In the sluggish part of a river, the water if warmer, richer in nutrients, and more
conducive to plant growth than it is upstream. Thus a large growth of water
lilies and other vegetation may shelter an abundance of insect life, reptiles and
There are rivers that are fast moving and those that are slow moving. Some
may be both at different stages. For this website we felt it necessary to
differentiate between the two. Some species of odes prefer fast moving waters,
while others prefer slow moving waters. If that's weren't enough, some odes
prefer sandy bottoms while others muddy or gravelly.
As in fast moving streams, organic materials do not accumulate so easily in fast
moving rivers, therefore the food source on fast moving rivers is usually limited.
Plant life is scarce and usually limited to the outer banks. Most aquatic organisms
are swept downstream by strong currents and turbulence. The fast currents within
the river produces riffles and rapid waters which are attractive to some very habitat
specific odes such as Riverine Clubtail (Stylurus amincola), Cobra Clubtail (Gomphus
vastus), Stygian Shadowdragon (Neurocordulia yamaskanensis).
Slow Moving River
When a rushing river reaches a flat expanse, it undergoes a change. The waters
spread out and slow down, depositing their load of silt and creating a soft muddy
or sandy bottom. In many cases the river becomes a series of meanders,
oxbows and horseshoe shaped bends. In the sluggish part of the river the waters
are much warmer and richer in nutrients, thus more conducive to plant growth than
it is upstream. When more plant life is present it produces a greater food
source for many insects and amphibians. A good variety of odonates are therefore
found inhabiting slow moving rivers, some species of the Clubtail family prefer
sandy bottoms such as the Elusive Clubtail (Stylurus notatus), Arrow Clubtail (Stylurus
spiniceps), Skillet Clubtail (Gomphus ventricosus), Common Sanddragon (Progomphus
obscurus), while others such as Prince Baskettail (Epicordulia princeps), Illinois
River Cruiser (Macromia illinoiensis), prefer muddy bottoms. And there are
those who prefer gravel bottom rivers such as the Phygmy Snaketail (Ophiogomphus
The biggest source of food in a stream is not the plants, but waste material
from outside the stream, especially where a stream runs through a forest, dead leaves
and rotting wood fall into the water and form a community of things, beginning with
bacteria, fungi and other living organisms that breakdown the dead materials.
These organisms form the slime around rocks and leaves in streams, and are the main
food source for aquatic larvae, allowing many insects to live beneath stones
In most swift streams, shallow riffles alternate
with deeper pools; where the gradient drops sharply, waterfalls and white-water rapids
appear. Because of the current and turbulence in swift streams, organic materials
do not accumulate easily. Thus the primary food supplies occur in a different
type of habitat within the stream, its riffle
regions. Riffles (regions where there are shoals and shallow rocky areas for
organisms to adhere to). Riffles appear as ripples visible on the waters surface. Few aquatic
plants other than algae and mosses appear on swift streams. Generally there is not
an overabundance of odonates either, but the ones that are attracted to them are
some of our less common ones, such as Snaketails.
Most fast streams mature and eventually turn into slow moving
streams. In a mature slow moving stream there is a progressive downstream
movement of meanders, leaving shallow or deep pools, backwaters and oxbow ponds. Water
in slow moving streams is generally warmer than that of faster streams,
allowing a growth of microorganisms, Since food supply is abundant, these
streams are dominated by aquatic insects and invertebratres. Many odonates
in their larval forms find this the ideal home. Some of the odonate diversity
found in bogs and fens may also be found in slow moving streams. Racket-tailed
Emerald (Dorocurdulia libera), Ski-tailed Emerald (Somatochlora elongata), Dot-tailed
Whiteface (Leucorrhinia intacta), Ashy Clubtail (Gomphus lividus), and a few damselflies
notably the Spreadwings (Lestidae), Broadwings (Calopterygidae) families. Plant
life in slow streams may include duckweed, ferns, mosses, cardinal flowers along
with algae mats.
Seeps are natural water sources where freshwater from below the ground flows
to the surface to form small streams. These habitats often consist of a thin
film of water that barely flows over rock surfaces, sometimes with a covering of
leaves and moss. Seeps can be found in forests, old pastures or fields, but
are often located along hillsides or at the base of mountains where groundwater
can be observed leading from crevices of rocks. Seeps usually remain wet all
year, but in extreme droughts may dry up. Seeps create valuable habitat for
a variety of rare plants and animals. Seeps are home to some of our most threatened
species of odonates such as the Spiketails (Cordul and Petaltails.