Winter rains have filled the ponds, causing them to overflow their banks, flood the gravel bar at the southeast end and the low area between the two ponds, and create a single, large pond. It now looks much like it did when I first saw it, causing me to name it in the singular – Little River Pond. It will remain like this until the rains stop and the heat of summer evaporates much of the water. Most of the gravel bar is under water and much of what isn’t, is just barely above the water level. I have to wonder how the tiger beetle and sand wasp larvae can survive in these conditions, but every spring the adults appear again. For now, though, the gravel bar is devoid of life.
Little River Pond showing flooded narrows
Not all life is silent, though. The bald eagles regularly fly overhead, giving their weak, high-pitched chirping whistles in antithesis to their massive strength. An occasional crow or raven gives out its rasping call and the local flock of red crossbills flies from tree to tree looking for seeds to eat and calling “jip, jip” as they go. chestnut-backed chickadees and song sparrows forage in the bushes around the pond, and from the small patch of woodland across the pond a spotted towhee gives a raspy “zreeee.”
Red Crossbill (photographed in 2007 in Edmonton)
On the pond you may hear an occasional “quack quack” from a mallard as the small resident flock forages among the flooded bushes between the two ponds. There are other ducks as well. The ring-necked ducks are usually present, but wary, frequenting the far shore and swimming into the bushes if they feel threatened. The two female buffleheads that are usually present don’t seem to be as wary, and if you are quiet they may swim close by you, diving regularly for whatever they can find on the bottom of the pond.
Earlier in the winter I had noticed a large number of freshly cut branches at the entrance to the beaver lodge. It was obvious that the beaver was stocking up on food for the winter. Beavers will remain active all winter long but will stockpile branches in the fall to minimize how frequently they have to go out foraging for food in the winter. During the summer months they feed on fresh green shoots and roots of plants, but in the winter they have to feed on tree bark, and for this purpose they will sometimes cut down quite large trees.
On one of my visits to the pond I had the opportunity to talk with a local resident, who told me that the beaver had finally felled a large tree at the west end of the pond earlier in the winter. I walked down to the west end and found the tree the beaver had cut down, a large cottonwood with a diameter where the beaver had cut it of about 60 cm (2 feet). Most of the side branches had been cut off and much of the bark on the main trunk was chewed away. Obviously this was the beaver’s source of food for the winter.
Cottonwood trunk stripped of bark
January has been rather average weather-wise, although I suspect that we have had less sun than average. Daytime highs have generally been up around five degrees and the warmest day hit nine. Although we have had a fair bit of rain as usual, and the occasional wind storm that typically comes down the Strait of Georgia, there has not been a major winter storm with a dump of snow this month. At Little River Pond no ice formed other than overnight ice in the shallow, flooded areas, which quickly melted as daytime temperatures rose.
Life in the water slows down in winter, but activity never completely stops. The only evidence of any fish I saw was a single fish jumping on January 1, most probably a sea-run cutthroat trout. This doesn’t mean that the fish aren’t there; they are simply not rising to the surface for insects. The adult cutthroats, which are typically found in sheltered estuaries and tidal lagoons, return to fresh water in late fall and early winter and spawn in late winter to early spring. The young stay in fresh water for two or three years before they migrate to the ocean.
I did a couple of sweeps with my insect net to see what I could find in the water. My net has a very fine weave so it collects even the tiniest arthropods.
The first sweep was shallow, through the vegetation, so that I avoided getting any of the bottom muck. I transferred it to a large plastic jar that I keep just for that purpose and immediately, even through the murky water, I saw life. A tiny predaceous diving beetle, probably less than 3 mm long, rose to the surface for a bubble of air. Then I noticed several damselfly nymphs swimming in the murky water. I decided to bring the jar home to let the silt settle out of the water.
By the time I got home it was obvious that the water was teaming with life. There were at least a dozen damselfly nymph, a number of caddisfly larvae, a couple of daphnia, several cyclops and numerous tiny arthropods that I finally decided must be clam shrimp. The last three were all around a millimeter or less in length, just barely visible to the naked eye.
I did my second sweep almost three weeks later, and this time I went deep into the muck, looking for larger aquatic insects. Sure enough, I dredged up two dragonfly nymphs, which was not in the least surprising as this pond has such a high number and diversity of dragonflies.
I also got a water boatman and a small predaceous diving beetle larva, also known as a water tiger, and this time there were lots of caddisfly of at least three types. It is these larger creatures that are necessary to sustain the fish population.
Water tiger with cyclops at lower left
With temperatures often ranging into the high single digits, I really expected to see at least a few insects and other terrestrial invertebrates. I was not disappointed – on almost every visit I saw at least one or two small flies, most likely midges of some sort. On one occasion I took the time to overturn a few logs, and on my third attempt I found several very active European sowbugs.
That same day I found a larger fly lapping up some juices from bark remaining on the cottonwood tree trunk that the beaver had felled. This is probably an anthomyiid, or root maggot fly, although according to Matthias Buck at the Royal Alberta Museum, there is a possibility it is a muscid. Flies in these two families are often so similar that it is impossible to identify them to family, let alone genus or species without collecting them.
Fly, either anthomyiid or muscid
Now, as the end of the month draws near, the days are getting noticeably longer and soon the first signs of spring will start to appear. But I’m not holding my breath; I know how cruel winter can be, and a serious winter storm is always a possibility in February. My one consolation is that here on the coast such storms are often followed by rain that quickly melts the snow away.
As winter’s winds roar down the strait
the pond lies silently,
broken only by eagle’s screams,
a small cacophony.
But all’s not dead, for in the pond
life stirs ’gainst winter’s hold.
A caddisfly, a diving beetle,
a dragonfly nymph bold.
And on dry land a thorough search
‘neath logs and dead leaf litter
reveals more life that’s active still,
sowbugs and other critters.
But most are dormant, most await
in silent slumber too,
for the first sign of spring’s return,
to begin life anew.
Note: I am posting this blog on World Wetlands Day, a day that is meant to draw people’s attention to the need to protect wetlands everywhere in the world. If you have read this this blog and not read the introduction, which was the previous post, I reccommend that you read it as it will set the scene for this ongoing blog and will also reflect the need to protect wetlands. You can find more information on World Wetlands Day here and you can find the introduction to The Pond blog here.
The young cutthroat trout swam warily through the water. At 8 cm ( just over 3“) long it was still quite small, even by fresh water standards. Cutthroats that stay in smaller fresh water ponds all their lives rarely get over 40 cm (16”) long and two pounds in weight, whereas saltwater populations can weigh up to twenty pounds. The cutthroat was looking for food, any insects would do. But right now it was not having much success. To avoid being taken by a kingfisher or a great blue heron it had kept to the centre of the pond and was hunting in deeper water, but lack of success had driven it in closer to shore. It was now searching amongst the emergent rushes along the shoreline.
It never even saw what hit it. Suddenly from the leaf litter at the bottom of the pond powerful front legs shot out and grabbed it around the middle and heavy spines punctured through its scales, holding it fast. It jerked violently as needle-like mouthparts pierced through its scales to its very core. The pain of the toxic digestive juices was overwhelming but all its struggles were for naught. As digestive enzymes turned organs and muscles to soup, its struggles became weaker and weaker until finally the life slipped from its body.
Giant Water Bug with Cutthroat Trout
The Giant Water Bug feasted for a full day before it was satiated. It was at its penultimate stage and it now had the body reserves it needed to go through the final molt to adulthood. It released the cutthroat which floated to the surface and became food for scavengers. It searched out a place close to shore in amongst the floating vegetation where it could stick its breathing tube out of the water while its old skin split down the middle of the back and the new adult, complete with wings, emerged. Even as the ponds top insect predator, this was a dangerous time for the giant water bug. Its new exoskeleton was soft and offered no protection, and even much smaller insects could attack and kill it at this stage. It would be several hours before its exoskeleton was hard enough to give it proper protection.
Giant Water Bugs are just one of many types of insect predators that are found in fresh water bodies. They are ambush predators, sitting amongst dead leaves and other debris at the bottom of ponds waiting for something to come close enough to grab. They are superbly camouflaged for this purpose. As well as taking other insects and small fish, they have been known to kill frogs, turtles and even snakes. Their bite is considered to be one of the most painful of all insects, and has earned them the name toe-bitter. The largest North American species is Lethocerus americanus, and the biggest of individuals can get up to 65 mm (more than 2 ½”) long. Females of this species, and others in the genus, lay their eggs in a mass on emergent vegetation. Females of other genera lay their eggs on the backs of the males. This affords the eggs better protection from predators while both aerating them and keeping them moist. In the tropics some giant water bugs can get up to 12 cm or more than 4 ½ “ long. There are about 150 species worldwide.
Adult Giant Water Bug
Predaceous diving beetles are another family of ferocious predators found in fresh water bodies. These beetles range in size from about 1 mm to over 44 mm (0.05 to 1.75”) in length. Unlike Giant Water Bugs they are active hunters, often searching the bottoms of ponds for their prey which mostly consists of other insects, tadpoles and small fish for the largest of species. Adult beetles are air breathers and have to regularly come to the surface to get more air. When they dive under the water they carry a reserve layer of air under their wings alowing them to stay submerged longer.
Predaceous Diving Beetle
The larval stage looks quite different from the adults and these are called water tigers. Like the adults the larvae are fearsome predators with needle like jaws. There are about 4,000 species worldwide.
A third group of aquatic predatory insects is the back-swimmers. This is another family of true bugs, and all species are active hunters. Unlike other aquatic insects they spend their lives swimming upside-down, hence the common name. Like the giant water bugs and predaceous diving beetles they swim with their back legs which are modified for that purpose. In the backswimmers those legs are exceptionally long and look very much like oars. These bugs are primarily insect eaters although the largest of species, which can get up to 2 cm (0.8”), will take small tadpoles and fish. They regularly come to the surface of the water for air, which they carry with them as a silvery sheen on the under surface of the abdomen. They are often seen hanging upside down at a 45 degree angle from the under surface of the water, ready to swim quickly downward if danger threatens or they see potential prey. There are about 400 species worldwide.
All three of the above families of insects have one thing in common, as adults they have wings and can leave the water and fly. They use this primarily as a dispersal mechanism. Most flights happen at night when the insects use the moon for navigational purposes. If you use the moon for navigational purposes, as long as you keep the moon in the same relative position in the sky and you do not travel for a long period of time, you will travel in essentially a straight line. Unfortunately when insects try do this in the presence of bright lights they end up flying in an ever diminishing spiral around the light until they come in contact with an immoveable object like a wall or the light itself. I am sure that everyone has seen the results on the wall behind their porch light or below a particularly bright street light are at the very bright lights at many gas stations. Inevitably this ends in the premature death of many insects. It has also earned the giant water bug another colloquial name, the electric light bug.
There are three other groups of aquatic “bugs” I would like to write about, actually two insects and a spider, but before this blog gets way to long, I will quit here and save the others for a second blog.
Death Stalks the Pond
Beneath the pond, amidst debris,
the water bug waits patiently.
She hides amongst the leaves so well
her presence is so hard to tell
The fish swims by unknowingly,
until it’s hit most forcefully.
Spined legs dig deep and hold it tight,
and needled mouthparts start to bite
Death stalks the pond
As on its flesh the bug does feed,
the fish provides what the bug needs,
to grow and molt and finally be,
an adult, its true destiny.
She finds a male, mates and with tact
lays rows of eggs upon his back.
And every egg has life within,
another cycle to begin.
And life goes on
©Terry Thormin July 4, 2012