Eco-Diary: Day 13 — I love turtles!

Here's how the creek looked on September 12:

You can't see it but there's a snapping turtle in this photo. Find it?

Here's another one, with the turtle's head exposed:

Here's a hint, in case  you need some help spotting it:

I would never have seen this turtle myself if it hadn't been swimming by just as I was settling down to do my observations. Of course, by the time I had my camera ready, it had stopped swimming and camouflaged itself almost completely in the weeds growing along the bottom of the creek. In fact, it was so still that after a few minutes of watching, I just assumed it had continued on swimming. I got on with my observations and thought that the little riffles in the stream were being caused by a stick lodged in some rocks.  It wasn't until I realized that the stick was sometimes there and sometimes not that I realized that it wasn't a stick at all, but the turtle's head poking out for a breath.

I did a little more turtle watching, but in the end, a turtle that looks like a stick poking out of the water at its most active eventually stops being enthralling. So I shifted my attention to the water bugs that were skimming along the surface in the quiet, shady part of the creek just next to the bridge. 

There were actually really hard to photograph because they hardly stopped moving; they were in perpetual motion, presumably hunting for smaller bugs. I'm not sure what species they are. According to The Water Striders of Ontario (published in 1970), there are 11 species in the province — which is fewer than I would have expected, but still too many for me to be able to identify which species my water striders belong to. Not surprisingly, most naturalists don't bother distinguishing between water strider species (when they even bother to mention them at all).

You probably learned in elementary school that water striders take advantage of surface tension to glide across the surface of the water without breaking it. The University of Toronto happens to have a faculty member who is an expert in water striders. In 2009 his research team identified the gene that is responsible for the striders' modified leg lengths and that, ultimately, enables them to walk on water (read the full text).

I've never thought much more about water striders until now, but they would be a great way of exploring the concept of surface tension with a science class. (And for even more physics fun, you could compare and contrast their use of surface tension against human-scale water-walking devices that use hydrofoil technology.)

One more thing: in addition to having exceptionally long legs that help distribute their weight, water striders are also covered with a dense coat of water-repellent hair called microsetae:

These microsetae create a cushion of air against their bodies, and also apparently help striders detect vibrations in the water, making it easier to find their prey

I also noticed this caterpillar tent for the first time today. I'm pretty sure it wasn't there before:

I had assumed it was the work of tent caterpillars, but according to local naturalist Drew Monkman's book Nature's Year in the Kawarthas, this is the work of the fall webworm. Tent caterpillars are only active in the spring, while the fall webworm, a member of the tiger moth family, spins its large, loose webs in the fall. The web houses colonies of small, beige, hairy caterpillars and remains on the tree throughout the winter. The caterpillars overwinter in the pupal (caterpillar) form. They leave the nest in spring only when they are ready to spin a cocoon and metamorphose into small white moths.

And as if that wasn't enough excitement for one day, just as I was about to leave, another snapping turtle came along. This one was much larger, and for a minute I thought there was going to be a turtle face-off, but the two seemed to pass each other by without much fuss. 

You can just see it through the shadows dappling the water's edge in this photo — more evidence of the snapping turtle's remarkable camouflage, which I'd never given much thought to before: