October 2009 – Seabrooke Leckie

Happy Hallowe’en!

Happy Hallowe’en, everyone! I’m recycling a jack-o-lantern photo from a couple of years ago, as we didn’t do one this year. It’s a Great Horned Owl (or supposed to be), with a mouse, which I’d carved for an owl-related event at the bird research station in Toronto.

We had no trick-or-treaters this evening. I didn’t really expect any, but I bought a small bag of chocolates just in case. We’re the very last house on a dead-end street that is sparsely populated to begin with, and I think there’s only one home with kids along its length, which is up near the crossroad. Rural homes, at least where I’ve lived, tend to get considerably fewer kids coming around, simply because the density of children in the area is lower. Most years my dad would drive us from house to house, and the three of us would pile out of the car and go up and ring the doorbell. For some houses it was the only time of the year we had any interaction with the residents, but you got to know most of them. This is the house that gives out cans of pop, that one has FULL SIZED chocolate bars, that one has homemade fudge, that one’s the dentsit’s and he gives you a toothbrush with your sugar-free gum, and that one gives you apples, yuk, don’t bother with there. The thing about our little rural community is that you could trust the apples and homemade fudge.

The upside to trick-or-treating in the rural areas is that you got to pop back in the car between houses, so you didn’t really get cold as you would if you had to walk through the neighbourhood. Also, because each house only got a few cars of kids, you could expect to receive generous amounts of handouts at each stop, particularly if you arrived later in the evening after the homeowners had given up on getting anyone but still had a big bowl of candy left. I recall one year my parents took us in to town to trick-or-treat, probably because we had a notion that with so many more houses in town, your haul would be doubled, but it ended up that we came home with about the same amount of loot, just cold and tired after having done twice the work.

My mom was very good behind the pedal of a sewing machine, and for several years made our costumes herself. If and when I have kids, I hope to do that also – they’re just so much more personal than one bought from a store. Raven’s the only youngster I’ve got right now. I briefly toyed with the idea of dressing her up and taking her around from house to house, not for the candy but just to meet people, which she’d looove. Instead, I pulled out a few pieces of old clothing and dressed her up as a Parisian artist. If I’d been thinking ahead, I would’ve done so during daylight hours when the light was better for photos…

Red in tooth, not claws

A couple of weeks ago, as Dan stepped outside one evening to bring Raven in from her tie-out (which we’ve started having to put her on, as she disappears off into the darkness at night and ignores our calls otherwise), he discovered this creature laying on the step. It was tiny – that’s my thumb included in the photo, partially for scale, and partially to prop the poor thing up while I took a couple of photos. It was dead, of course; we presume Raven caught it and killed it, but if she had it would be the first thing she’s killed, to our knowledge. Even the chipmunk she managed to catch some time ago she just pinned under her paws, apparently confused about what to do next. Perhaps it was already dead and she just picked it up and brought it back, liking the way it smelled. Perhaps she caught it, but in doing so she literally scared it to death – small animals can sometimes become so stressed out when captured that the stress itself will kill them (I’ve had it happen once or twice over the years of bird banding and it’s distressing; fortunately, in the some 20,000+ birds I’ve handled, a couple of times is an exceptionally rare occurrence, and virtually all are just fine).

Wherever it came from, and however it died, the poor creature was now on our doorstep. Dan brought it in and presented it to me because he knew I’d be interested in it for the blog (he always gives me the sweetest, most thoughtful gifts). Taking a closer look at it, I identified it as a shrew, probably a Masked Shrew, Sorex cinereus, the most common shrew of four possibilities in our area, as well as through the rest of its range across Canada and the northern US (hence its other common name, Common Shrew). Contrary to its name, it doesn’t have a well-defined mask; the websites I visited didn’t give a reason for this label.

Shrew, mouse or vole, how can you tell them apart? Shrews belong to the taxonomic order Insectivora, while mice and voles are in the order Rodentia. Members of Rodentia, the rodents, have long, sharp upper and lower incisors that grow their entire life. Shrews, however, do not; they are born with a single set of teeth (they actually replace their baby teeth before they’re even born) which wear down over the course of their life. Shrews also have five toes on their feet, while rodents only have four.

But probably as you’re watching something scamper across your yard you’re not able to get a really good look at its incisors or its toes. That’s okay. At least here in North America, you can tell the shrews from the mice by their elongated nose and somewhat big-headed appearance. Voles are larger, chunky rodents, looking a bit like a cross between a mouse and a guinea pig. The ears are often nearly hidden in a shrew’s fur. Some shrews will have shortened tails, but the Masked has a longer tail more like that of a mouse.

I spent a great deal of time flipping back and forth on the ID of this critter while I was taking the photos. There didn’t seem to be a defining marking in the coloration that would identify it as either a Masked or Pygmy. The Masked Shrew didn’t really show a mask, and the Pygmy Shrew wasn’t significantly smaller than the Masked, on average. I gather the Masked is sometimes more brownish and the Pygmy more grayish, but it’s a subtle distinction, and hard to decide on when you’ve only got the one shrew. Finally, I found a site that indicated you could tell them apart by their teeth – the side teeth immediately behind the incisors, called the unicuspids (similar to our canines), are all the same size in Masked, but the back ones are smaller than the front ones in Pigmy. I’d say these look to be about the same size.

Shrews in the genus Sorex (as well as others in the subfamily Soricinae) have red-pigmented teeth. Members of the subfamily are actually known as “red-toothed shrews”. The colour comes from iron deposited in the enamel of the tooth, which serves as a strengthening tool, hardening the enamel against the constant wear of day-to-day life, which is why it’s mostly found concentrated at the tips, where wear is greatest. I don’t know why only some shrews have it and others don’t, though.

The shrew’s face is covered in long, bristly whiskers. In most animals, long whiskers are associated with sensory functions, either of the surrounding habitat, or playing a role in food acquisition in insectivores. Think of birds, for instance, where species that hunt and chase insect prey, such as flycatchers, have lots of bristly whiskers, while those that eat seeds or tend to just pluck relatively stationary insects from foliage, such as most warblers, do not. The Masked Shrew eats primarily invertebrates such as insects, worms and snails, but is opportunistic and will take small vertebrates such as salamanders if given a chance, or seeds if living food is hard to find. Shrews have small eyes compared to mice, which feed mostly on seeds and berries and therefore require good eyesight to locate their food. Shrews rely on their sense of smell and touch. Their long, prehensile nose probably also plays a role in this.

Shrews are active year-round, and their trails can often be seen in shallow snow in the winter, where they plow a channel-like path compared to the leaping footprints of a mouse. Usually their trails dive down into the openings of melted snow around the base of trees and rocks, rather than tunnel up (or down) through the snow. Ontario Wanderer posted some good examples early last year (one of the front-page results that came up when I googled “masked shrew Ontario”).

Tay Meadows Tidbit – Canid skeleton

A couple of days ago I took Raven over to the 100-acre woods for a walk. I didn’t want to be out too long, and I debated between doing the forest loop, or walking back into the fields and returning via the back end of our 30 acres (an old railway bed, now an ATV trail, runs along the back of the properties providing a convenient off-road connection). I finally decided on the latter, mostly because I hadn’t been back there in a while, more than because I thought I’d see anything interesting. And for most of the walk, this held true; I didn’t see much aside from a few small flocks of birds, and since I hadn’t brought my telephoto lens, by the time we were reaching the railbed I still hadn’t taken any photos.

Right at the edge of the property there there’s a clearing with some exposed rock and some interesting boulders. I thought I’d maybe go check them out, just on a whim. I crested the crown of the rock, and on the other side spotted something white. Suspecting a skull, I went down to investigate. I was correct, it was a skull, but the skull was accompanied by nearly a complete skeleton. How cool!

I took a few photos, but mostly left it undisturbed. I briefly toyed with bringing it all back and trying to assemble it like a jigsaw puzzle, but I had nothing to carry it in, and what would I do with an assembled skeleton, anyway? I’m not the sort to display something like that in my living room, or even in my study. It was quite small, the whole pile probably only about 15 inches (38 cm) across, and I just figured it was something common, like a raccoon. The skeleton’s proximity to the highway, just a couple hundred meters/yards away, made me suspect that the animal had been hit but not killed on the road, and staggered here where it collapsed and eventually died. Probably it was picked over by scavengers and decomposed by carrion beetles and other invertebrates, allowing the bones to remain mostly together. The only thing I didn’t see there was the lower jawbone. Somebody may have picked it up and taken it away.

This evening, as I was starting this post, I decided to key it out just to be sure about the identity. I’ve kept most of my textbooks and lab manuals from my university courses (at least, those courses that I found interesting), including A Manual of Mammalogy that has more information than you’d ever think you’d need to know about how to identify mammal families by their skulls, as well as other useful lab and field techniques. It would have helped me considerably to have the lower jaw in the photo, since part of keying out skulls is using their dentition formula (number of upper/lower incisors, canines, premolars and molars, which differ in pattern/formula by family), but I made do. I reached the end of the key with the result that the skull didn’t belong to a raccoon at all, or even an opossum, my other suspect, but in fact was a member of the Canidae – the dog family.

Well, that surprised me a bit. It would have to either be a Red Fox (Vulpes vulpes) or a domestic dog, as it’s much too small to be a coyote (or a wolf, which I wouldn’t expect around here anyway). This key to North Dakotan mammals suggests Red Fox skulls to be 12.5 to 15.5 cm (5-6 inches) in length; the skull would fit at the small end of that range. Though most dogs have a high, sloping forehead, some long-nosed breeds might not show this as distinctly. I’m not sure if there’s a feature visible on all domestic dog skulls that can be used to tell them apart from wild canids, but I suspect there probably isn’t, so it’s likely impossible to rule out a small dog. However, since dogs are generally (though not always) kept in their owners’ yards, a fox is probably more likely to become roadkill.

I may go back and collect the skeleton after all. I’m still not sure what I’d do with it, but a Red Fox is a pretty cool find, not something you stumble across every day. It would also allow me to confirm (or correct) this ID, since I keyed it out just using the photos I’d taken, which obscured some features. It’s interesting to examine skeletons; since they’re on the insides of our bodies, they’re not something you get to see often.

For instance, I hadn’t noticed that the vertebrae have two lateral holes to the central main one (this may, perhaps, have been something learned in mammalogy class but since forgotten). The latter is, of course, where the main spinal cord runs, but the smaller holes allow passage of a main artery and vein and some smaller nerve bundles. The projections of bone to either side provide points of attachment for various muscles.

In the second photo, of the skull, you can see a long, thin arch running along the cheek. This is basically the fox’s cheekbone. In the front, it forms, in part, a portion of the eye socket (the remainder would have been cartilage that would have decomposed). In the back half, the lower jaw bone slots up inside, and the giant masseter muscle, which clamps the jaw shut, runs through the inside of the arch and attaches to a spot higher up on the skull. It’s this long length of the jaw muscle that gives it so much power.

Your own muscles do something similar. Put your fingers on your cheeks and clench your jaw a couple of times. You can feel the muscles contracting. Now move your fingers to your cheekbones. Nothing, right? Finally, put your fingers on your temple and clench your jaw again. There’s the muscle again. Neat, huh?

Sunday Snapshots – October on the Grand Trunk

No, not the Canadian railway, nor the Asian road route, nor the Ankh-Morpork telegraph system (which I recently finished reading about). This particular grand trunk is growing in our front yard and belongs to a large, old maple tree. The trunk is covered in deeply ridged bark, which is in turn covered with colourful lichens, which in turn hosts many interesting critters.

I was out raking leaves yesterday, since the weather was quite mild; a relatively balmy 16 C (61 F). I set aside the rake before the sore spots on my thumbs got a chance to turn into blisters, but reluctant to go in just yet, I played ball with Raven for a little bit. In between tosses, while she was hunting for the ball in the long grass of the meadow, I examined the trunk of the tree. It initially caught my interest when I noticed some of the tiny little Bark Mycena that I had first observed on the maples of my parents’ old house, when my blog was still just a month-old fledgling.

I grabbed my camera and documented all the organisms I found on the trunk, between the ground and eye-level, yesterday afternoon. For the purposes of relating scale, all of these photos are taken at the same magnification and are the original out-of-the-camera image; I have not cropped any of them (although I did lighten a few since it was overcast and some of the photos were a little dark). Most people know how big an average pillbug (or maybe a sowbug; I forgot to check for tails) is – the size of the frame for the photos below is the same as for this one, to give you an idea of relative size. The only exceptions to this are the final three, which were too big to fit into the frame when fully zoomed-in.

bagworm moth case — Bagworm moth case; probably the adult has died and it's full of eggs

Saddled Leafhopper, not technically on the trunk, but very close. Note the greenish leafhopper in the upper left.

tussock moth caterpillar — Tussock moth caterpillar, very worn; maybe Banded or Yellow-based

The next three are at a different scale from the above, as they were too large to fit into the frame comfortably (or at all). They were also on the next tree over, so not strictly the same group, but I couldn’t resist including them as well.

Polyphemus Moth caterpillar - similar to the Luna Moth cat but separated by the V-shaped mark on its rear end

Tay Meadows Tidbit – Woolly aphid

Moths aren’t the only things attracted to lights at night, and I tend to get a lot of non-lepidopteran insects in the trap, though moths make up the majority of the catch. The other night I found half a dozen of these guys on the egg trays. I’ve seen them, or things like them, before, but most of the time I’m preoccupied with the moths and don’t bother with photos of most of the rest of the stuff (once I’m proficient with moth ID, then I’ll start worrying about the other stuff in the trap). There weren’t too many moths in the trap this week, though, so I could take a few moments to check out these critters.

They were quite small, perhaps only 5 mm (<1/4″). The most noticeable thing about it was the fuzzy bit poofing out from its back end, under its wings. It looked like a bit of blue cotton batten that had gotten stuck to its abdomen. Its body was a lovely shade of indigo gray. It had long wings that projected some length beyond the end of its body. At first glance it looks a bit like a fly. The proportions of the wings give it away as an adult aphid, though; flies’ wings are never that long.

Specifically, it’s a woolly aphid, perhaps Woolly Alder Aphid, Paraprociphilus tessellatus. They have two forms, a wingless and a winged adult, both of which are covered in fuzzy hair-like projections that give them their name. Individuals of the wingless form cluster together in a mass on the branch or twigs of their host trees, looking a bit like a fungus gone wild. I’ve never seen a group of woolly aphids like this, and their weirdness had sort of placed them in that group of “organisms that other people see”. So I was surprised when I looked this one up, and submitted it to BugGuide.net for ID, to discover that it was a woolly aphid adult. It makes sense, though, with a woolly abdomen like that.

In both forms of adults, the “wool” is not actually hair at all, but wax it secretes into long projections. There are a number of species of woolly aphid, of varying colour, though they seem mostly to be pale. The fuzz is thought to serve a couple of functions. First, it acts as both camouflage and defense against predators. Second, it may have thermo-insulative properties, both protecting against sun in summer and against cold in cooler months.

In the case of the Woolly Alder Aphid, they overwinter as eggs in crevices in the bark of maple trees, although one website suggests the woolly clusters might also be able to survive the winter tucked out of sight somewhere. The individuals that hatch out in the spring are all females. They find themselves a new maple leaf and attach themselves to the midvein, where they slurp nutrients from the sap. These females reproduce parthenogenically; that is, without the aid of males. The live young they produce are also females, essentially clones of their mother. Around mid-summer, something in the way they produce their offspring changes, and the now-sizable colony begins producing winged females. These winged adults fly away from the maple tree in search of an alder, where they spend the rest of their summer, once again reproducing asexually, without males. Just before winter, the colony again begins producing winged adults, but this time of both sexes. The males and females get together on maple trees where they mate and the female lays eggs that begin the new generation the following spring. It would be these pre-winter adults that I attracted to my trap. I don’t know if you can tell apart males and females.

Aphids can produce up to 12 generations in a single season. Apparently, if every individual descending from a single overwintered female survived for the entire summer, by the end of the year her progeny would weigh the equivalent of 600 million people. Good thing they don’t live all that long. When the winged adults are produced, just before they take off for their next destination they cluster on the leaf or twig with their parent colony. If disturbed while doing this, they will take to the air, looking a bit like you just brushed a dry dandelion head and sent all the seeds drifting off. Their appearance as drifting bits of fluff while on the wing has lead to the colloquial name of “fairy flies”.