mammals – Page 10

Muskrat in our meadow

I spent the last couple of days at my parents’ new place, house-sitting for them as they returned to the old house one final time (hopefully) to complete the paperwork for the sale of the property. I returned home this afternoon, in the rain. When I got home, Dan asked me if I’d seen the muskrat. He took me out to the side of the house where he’d seen it last. It wasn’t in the same spot, but a peek into the two basement window wells turned up the little critter. Dan commented that it had already fallen into one of the wells; this time it was in the other. It was just hunkered down in a corner, looking a little soggy and disgruntled but otherwise fine.

It was small, and appeared to be a youngster. Heaven only knows what it was doing way out at our house. Although there are tiny little ponds here and there, the closest significant water source is a marsh-bordered creek a kilometer (0.6 miles) away. Presumably it was dispersing from its natal territory, looking for a new place to call home. Muskrats have relatively quick breeding cycles, with the female giving birth a month after mating, and the young weaned and independent at just six weeks of age. The female may have two or even three litters in a summer, often giving birth to the subsequent litter before the first one is completely weaned. They can potentially have three litters in three months, each bearing five to ten young. That’s a lot of baby muskrats! It comes as no surprise, then, that they suffer a high mortality in their first year, and the high birth rate has evolved to counteract that.

Dan scooped him up in my butterfly net to get him out of the window well, and deposited him in the grass. Muskrats even when full grown don’t get that big, only about 1 kg (2.2 lb) on average, and 50 cm (19.6 inches) long from nose-tip to tail-tip. About half of that length is tail. Their tail is flattened vertically, like a fish’s, and is used in the same manner while swimming. Although they superficially resemble beavers in their general shape and scaly tail, they’re actually more closely related to field mice, being, essentially, a large field mouse that has adapted to life around water. Beavers and muskrats and field mice all belong to the same order, Rodentia, so it’s not surprising then that they should seem similar.

Once released from the net, the muskrat scurried across the grass to the nearby lilac bush. He could move quickly, and I just got one sort of blurry shot before he was in the shrub. They’re most at home in the water, however, and spend the majority of their life in or near it. They build their burrows into riverbanks or along lake or pond edges, with the entrance to the burrow underwater. In the winter, they create “push-ups”, hollow mounds of vegetation that protrude through the ice, in which they can eat and rest undisturbed. I found a few of these last winter.

They get their name, muskrat, from their resemblence to rats (even though they’re more closely related to mice), and from two musk glands they have near their anus. In the breeding season these swell and exude a yellowish musky substence that the muskrats use to mark locations along frequent travel routes such as their lodge or conspicuous land features. The purpose of the scent marks isn’t clear, but is thought to be a form communication between individuals, perhaps within a family group, or maybe as territorial markers.

Once in the relative safety of the lilac bush, the muskrat hunkered down and wouldn’t budge. Check out his feet in this photo. Those long claws are used for digging in banks when building their burrows, as well as in foraging underwater. Much of their diet is made up of cattails, especially the roots. Many nights at our last house we’d hear the sound of chewing coming from down at the lake edge. There was a muskrat that had a burrow in our shore there, and he’d often make meals of the cattails that lined the banks. We rarely saw him during the day. If cattails are scarce, muskrats will also eat other aquatic vegetation such as bulrushes, horsetails or pondweeds. And if plant matter in general is hard to find, they can and will turn to protein sources such as fish, frogs or even clams. That would explain all of the empty mussel shells we’d see around our shoreline.

Unlike beavers, muskrats only have a moderate amount of webbing on their back feet. Most of their foot power is from hairs that line the toes, creating a paddle-like effect. They use their feet mostly when swimming at the surface, where their tail acts as a rudder. When underwater, their tail provides most of the propulsion, and their feet help with the steering. They have the ability to slow their heart rate and metabolism, and have a high tolerance for carbon dioxide in the blood, the combination of which allows them to stay underwater for up to 15 minutes at a time.

When I got a tad too close with the camera, the muskrat bared his teeth and even lunged at me. He was fierce! While they’ll usually escape to deep water if they have the option, muskrats are very courageous when confronted on land, even if not cornered. They can be very vicious, inflicting deep wounds with those sharp rodent teeth. Despite this, they suffer heavy predation from mink, as well as snapping turtles, pike, coyotes and wolves, fishers, wolverines, lynx – basically any large carnivorous vertebrate.

The sharp cutting teeth are primarily used in chewing vegetation. Muskrats are specially adapted for eating underwater, something that most land-dwellers would be unable to do. Their front teeth project in front of their cheeks, and they can close their heavily muscular cheeks behind their incisors, essentially closing off their mouth and airway while they’re cutting vegetation. Once they’ve cut some food, they can close the front of their mouth and open their cheeks to allow them to chew and swallow it.

After I’d run off a few photos, we backed off and let the little guy be. We kept Raven inside to allow him to wander off without being harassed (also for Raven’s safety – she could get a sharp bite on the nose if she got too close, which undoubtedly she would). When I went back out to check on him after an hour or two, he was gone, and I was unable to relocate him. Hopefully en route to better habitat than our grassy meadow.

A girl’s best friend is her horse

I spent the evening at my sister’s place today, to try to take some portrait photos of her with her horse. I didn’t quite achieve what I was looking for with the batch we got this evening, and I suspect I’ll be making another trip there.

I had planned to do up a post on milkweed this evening, but I got in later than expected, and am rather tired. So, in a tribute to (mostly) Wordless Wednesday, here are a few of my favourites of the 210 exposures, even though they’re not really nature-themed.

L’otter fun

At our Rock Ridge visit last week, I was sitting at our banding station when I heard some unfamiliar yelping coming from the north end of the lake. I couldn’t see anything at first, but as I peered through the trees toward the water I finally spotted some splashing. I thought ducks, initially, although the calls didn’t sound like ducks. It was only as the animals drew closer, moving south along the lake, that I could identify them: river otters!

Anticipating that their movement along the length of the lake would hopefully bring them near enough for a few distant photos, I grabbed up my camera and telephoto lens and was able to run off a few shots as they passed below me. It was difficult to count them as they splashed and dove, as they were rarely at the surface all at the same time, but I guessed there to be six individuals. They seemed to be diving underwater and resurfacing with food, although I couldn’t tell what it was they were eating.

Probably, though, they were catching fish, which make up the bulk of an otter’s diet. Otters are extremely well-adapted to life in the water, being streamlined with webbed toes and a strong tail that provide extra agility when hunting or playing. When I was out in the canoe on our previous visit I noted many smaller fish in the waters of Rock Lake, so there would be plenty to eat. Otters may supplement their diet with other small, aquatic animals such as frogs or crayfish.

Because of their aquatic lifestyle, otters have some unique adaptations. One of them is asymmetrical lungs. An otter’s left lung is nearly 20% larger than its right, and has four lobes compared to two for the right. This probably helps with how long the otter can hold its breath when it dives, increasing lung capacity and surface area for oxygen absorption. They can remain underwater for nearly 4 minutes, diving to depths of up to 20 meters (65 feet).

At this time of year, it’s most likely that they were a family group. In the early spring, after mating, the female sends her mate off for a bit of privacy while she gives birth to and does the initial raising of her litter. At about three months the kits are old enough that the mother begins teaching them to swim and hunt. The father rejoins the group once the young are about six months old, helping with their education. It seems a little early yet for the father to have joined the group, as six months ago means the young would have been born in February. Females may give birth to up to six young, so it may be she just had a large litter.

Otters are extremely social animals, an uncommon trait among mammals that live in our area. Mates spend half of the year together (the part when the young are grown), and family groups usually hunt and play together. Even adults aren’t opposed to a little fun, and may join the youngsters in games of tag or wrestling, or sliding down snowbanks or muddy embankments. They talk to each other constantly, and the entire time I watched them there was an ongoing dialogue of chirps and whistles.

The species is found through much of North America where lakes and streams are abundant, absent only from the drier Great Plains and arid southwest. Despite this, I’d never seen one before, so I was pretty excited by this encounter.

I apologize for the short absence; I was away for a couple of days and we’ve recently been having some technical difficulties with our internet that I hope will sort themselves out. I’ve had this post sitting since yesterday evening, waiting for our connection to come back online long enough to upload the photos and insert them into the post.

A mouse with wings

A couple of evenings ago, Raven was giving her alarmed something-strange bark, rather than her usual I’m-bored play bark, out at the front of the house. Usually when she does this there is actually something worth investigating (even though we don’t always find it), such as a turtle. That evening when I stepped outside, I could hear chittering coming from the rafters of the roof overhang above the front porch. Closer investigation revealed a small group of bats tucked up between the thick support beams and the side of the house.

I believe they’re Little Brown Bats, Myotis lucifugus. Little Browns are a very common species through Ontario as elsewhere, and are the most widespread and common of Canada’s species. They are often found roosting in attics or chimneys of houses, something that most other species don’t do, or do infrequently. Little Browns will give birth and raise their young in communal maternity roosts, which they will use year after year, often returning to the same one where they were born. My parents’ old house had one such roost in their attic, I think. Other night-time roosts may not be used as regularly, and indeed I think our Little Browns only stayed a couple of nights (perhaps they were put off by the flash of my camera).

When I stepped out to see what Raven was barking about, I found this mess all over the front stoop. Bat droppings, they looked a little like mouse droppings only larger, and were concentrated directly below the roost. Although I don’t think it was likely to do any good here, bat guano can be a very useful thing. In some areas, it’s collected from caves and used as a high-quality fertilizer. The bacteria harboured within it can also be used for detoxifying waste, improving detergents, and creating antibiotics.

Bats are the only mammals that can truly fly; other mammals may glide but are incapable of sustained flight. Their wings are thin membranes stretched across long bones that are modified hand bones. They catch their food, flying insects such as moths, beetles and mosquitoes, in flight. Small insects are snagged in their mouth, but larger ones may be caught in a pouch they form by curling forward. their back legs and tail, which also have membrane stretched between them to act as a rudder in the same manner as a bird’s tail.

The scientific name Myotis means “mouse ear”, and indeed their faces do have a mousey look. I really like bats, and since they’re big consumers of mosquitoes, am happy to have them roosting at our house. I hope I didn’t scare them away for long. There’s a bat box above the door, perhaps they’ll return to use it.

Monday Miscellany

I never did get around to posting any photos from our most recent visit to Rock Ridge, with the exception of the unboring beetles. That’s not for lack of any, however. I’ll probably recycle some of last visit’s photos into the post on our next visit (tentatively scheduled for Thursday, weather permitting). However, I’ll also post a couple here. This first one is a posed self-portrait (about the only sort of photo I get of myself, since I’m usually the one holding the camera) looking out over the main lake at Rock Ridge about an hour after sunrise. I’m not aware of a name for the lake, and in fact many of the lakes in the park are nameless, or at least lack any sort of official designation. The same was true of Hemlock Lake over at the first MAPS site (we gave the lake that name). Given that this site is Rock Ridge, perhaps I should start calling it Rock Lake? We’ll have to ponder that on the next visit…

This photo was taken on Big Clear Lake, one of the larger “perimeter lakes” that border the edge of the park. True to its name, the lake is both big and clear. On sunny days it’s easy to see the bottom even ten feet down. The clear waters imply it’s an oligotrophic lake – “oligo” meaning few, and “trophic” referring to the food chain. There’s not a lot of nutrients in this lake, possibly as a result of a granite bottom, and so there isn’t a lot of algae growing in the water column. Lack of algae means lack of plankton, lack of plankton means lack of aquatic insects, and all the way up. That’s not to say that there’s no life in the lake, just that compared to lakes with lots of nutrients this one is relatively depauperate.

I came across this beaver jawbone at the site, nestled in a bed of pine needles. The yellow teeth are characteristic of rodents, and their relative length and the overall size of the bone identifies it as a beaver. Beavers have sharp, strong teeth that grow through their entire lives. They need to be constantly chewing on trees and branches in order to keep them worn down. If they stopped chewing, the teeth would eventually grow into the roof of their mouth and make it impossible for the animal to eat. It’s possible that this bone was the kill of one of the wolf/coyote packs in the park, or it may simply have been a beaver that died of natural causes.

These Olympia Marble caterpillars were found crawling about the tip of a stem of woodland phlox that had gone to seed. The long, thin projection in the foreground, and the one that the little caterpillar is on, are both seed pods. I’m not sure if they were actually eating the seed pods or stem, or if they were there looking for a place to pupate; probably the latter, as the hostplant for the species is given as rockcress, not phlox. I mentioned the adults in another post a few weeks ago, found in similar habitat.

As we were leaving the site we noticed a couple of fish in the short, shallow creek that joins Big Clear Lake with “Rock Lake”. They were close enough, and the water clear enough, to get a passable photo. This one is a Pumpkinseed, identifiable both by the red crescent at the back of the black “ear flap”, and the red and blue striping on the cheek. They look considerably different when out of the water, however, the blue fins don’t really show up and the fish’s body looks green, not brownish red. They’re a common species that I’ve encountered in all of the lakes of the area, or at least those that I’ve looked in.

And a few steps further up the path (okay, so this post ended up being mostly about unposted photos from Rock Ridge), this fishfly flew in front of me and landed on the underside of this branch, where he obligingly stayed put so I could photograph him. I’ve talked about fishflies before, but the ones I’d seen were in the other fishfly genus, Chauliodes. This one is in the genus Nigronia, which have white patches on their wings, and is probably N. serricornis.

We’re starting to pack up the house in preparation for our move, now only a week away. Merlin and Oliver try to help, though I’m not sure they really lend much to the operation. There’s just something about an empty box that a cat can’t resist. We’ll have lots of packing to do, more than the last time we moved – at the time, back in Toronto, half my stuff was already boxed and in storage, which made it a bit quicker. We’re renting a truck and hopefully will be able to do it all in one day, if we’re prepared ahead of time.

And finally, this is a screenshot taken of the front page of the Nature Blog Network toplist. For the first time since I signed up, I’ve made the front page! I’m listed right behind one of my favourite blogs, too. I post this not to gloat, but because I’m proud to see something do so well that I’ve put so much time and effort and devotion into over the last year and a half. Of course, ultimately it’s my readers, all of you folks, that I really have to thank. Without you, I would still just be blogging away to myself. I know that I often fall behind on comments in trying to keep juggling all the balls of my life, but know that I read them all and I really appreciate hearing from everyone! And I do hope to eventually reply to them all (if I get organized, maybe I’ll even start keeping on top of it…).