Skull mystery

White-tailed Deer skull, antlers removed

On occasion when hiking our 30 acres, which has minimal forest cover, I like to walk back along the narrow strip of mature forest that borders our western fenceline. For most of its length it’s only half a dozen meters/yards wide, although there are a handful of spots where it reaches out into the meadows. I wander through, looking for anything different going on there than I might see in the field a short distance away. I stick to our side of the fence even though it’s an old split-rail that would be easy to hop, primarily because we aren’t sure who owns that land and I feel uncomfortable trespassing unless I know the owners never visit the property. But there’s one spot where our section narrows and has become choked with the invasive prickly ash. If you’ve never had the opportunity to try crossing a prickly ash thicket, it’s rather like trying to push your way through a rose hedge. Yeah.

So I hop the fence there and just skirt around the small patch of prickly ash, and hop back and carry on my merry way. Today as I was doing my brief bit of trespassing I happened across this fragment of bone. Picking it up, I noticed it had the round knobs at the back which are the bit of the skull that articulates with the spine. But this clearly wasn’t a complete skull – the front half was missing. Sheared clean off, in fact. I puzzled over it, took a few photos, and left it where it was. What had it belonged to? What had sheared it away? Could a predator slice bone that cleanly?

White-tailed Deer skull, antlers removed

It was only after I returned home that I had the thought that this might be a deer skull that a hunter cut. It was about the right size for the upper half of a deer skull, and comparing it to images on the web, it seemed to have a similar rear profile. I knew that deer antler trophies are sometimes mounted still attached to the poll of the skull. Further investigation (including this instructional video on how to prepare your own such mount, start to finish from a fresh deer head… not for the squeamish) revealed that the skull is cut with a hacksaw in a wedge behind and in front of the antlers, which pretty much confirmed for me what this bone seemed to indicate. Rather than just sever the poll, though, it appears our local hunter cut the back of the skull off first, and then removed the antlers second.

Although we’ve never met the folks who own that property, we’ve heard them out on their ATVs on rare occasion, and a couple of weeks ago I heard gunshots from that direction. This skull is much too old to have been this year’s, weathered and green with algae as it is, but it’s undoubtedly the remains of one of their kills. I’ve been through that area several times since last year’s hunting season, and as the fragment was lying out in the middle of a rocky bit, it’s unlikely I’d simply missed it before. Which presents another mystery: how’d this old bit of bone get there? It seems much too old for anything to have interest in chewing on it for the marrow. I have no answer to that question; it will have to remain a mystery.

White-tailed Deer skull, antlers removed

The sawed-off portion does present an interesting cross-section of the bone, however, something not typically seen when examining skulls or other bones. We’ve been taught that mammal bones are solid while bird bones are hollow, but neither of these are strictly true. Bird bones are actually filled with many struts that brace the two walls and give the bones strength. Mammal bones are filled with tiny holes and channels that give it a very porous look. In addition to making the bone lighter to carry around, these holes serve an important function: they are the channels that carry blood vessels through the bone network so they can access the marrow inside (the part of the bone which produces new blood cells).

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Visitor for Thanksgiving

White-tailed Deer

I hope everyone had a great holiday weekend! We had an enjoyable, relaxed Thanksgiving, a small event with basically just the immediate family. Although most years we’ve had our get-together at my parents’ place, this year I offered to host it, as I was the most central location and it would mean my youngest sister, who had an ill cat requiring regular care, wouldn’t have to be gone for as long. It also only seemed fair for us daughters to start taking over the hosting duties, my mom having done it for the last 30 years. Thirty years from now, I hope my children start taking over hosting, too…

The other, slightly more selfish, reason for offering to host is it meant I didn’t have to drive anywhere. This worked out pretty well, despite having to spend some time tidying the house prior to the arrival of the guests. Prior to dinner, my younger sister stepped outside to grab something from her car. Half a second later she was inside again. There was a deer out in the yard! Surprisingly, it hadn’t bolted when she’d bustled out the door, and so we all got up and went to the windows to watch it for a little while.

White-tailed Deer

I’m fairly certain that this is the same young buck that Raven and I startled in the back fields a week or two ago. We had been following the trail, both of us distracted, watching the path or the grass or something. As we came around a corner, there was a deer, not fifteen feet away. I just caught the briefest glimpse of him before he bolted, enough to note the thin, prong-less antlers. Raven, though likewise startled initially, gave chase before I could grab her or halt her with a command. She followed him off into the forest, where I gather the deer lost her, or she gave up the chase. She was back a moment later, apparently satisfied and ready to carry on down the trail.

White-tailed Deer

Clearly she was channeling her inner wolf. Grown male deer usually range in weight from about 130 to 300 lbs (60-130 kg), though larger individuals have been recorded. Given the lankiness of this youngster, and his apparent age, I would guess him to be on the lower end of that scale, maybe 150 lbs. Raven, at just 45 lbs (21 kg), is less than a third his size. However, this isn’t the imbalance it might seem at first. Historically, the only canid to prey on deer was the wolf; the rest lacked the size and strength to bring down these large mammals. More recently, northern coyotes, including those in Ontario, have begun to fill in this niche. Coyotes used to be only a western species, but started to spread east through Manitoba and Minnesota, and around the Great Lakes. Those that expanded south of the lakes retained their coyote characteristics, but those that spread through the north met and hybridized with wolves, thus acquiring some of their traits. (See this post at my mom’s blog for more about the research examining the two populations.) Larger bodies and bigger, stronger skulls and jaws, meant that they could exploit the abundant food source found in deer. These coy-wolves can be 30-45 lbs (14-21 kg), with the males growing larger than the females. I doubt Raven would’ve had any idea what to do with the deer if she’d caught up to it, however; it was probably just instinct, and perhaps some of the border collie in her, that made her chase a fleeing animal.

White-tailed Deer

The deer grazed for a bit beside the driveway, then wandered around the cars and over to the little apple orchard the landlord planted many years ago. There’s only a few trees inside the fenced-off enclosure; they look like they haven’t been pruned in a few years, but they’re still producing nice-looking apples. Where the branches overhang the path the apples are in easy reach. He snagged one and pulled it off.

Deer are opportunistic feeders. They are ruminants, like cows and other ungulates, and have a four-chambered stomach that allows them to eat a variety of foods and forage. The young buck was grazing on the grass by the driveway before moving over to the apple trees. Their diet varies according to season. In the fall, particularly in bumper crop years, acorns can make up a large part of their diet. In the winter, when snow cover is thick, they will often feed on bark. They have the ability to digest some foods, such as certain mushrooms, that would make us sick. Even though we think of them as vegetarians, a deer will eat baby birds from a nest if it finds one. When I was working in British Columbia as a bird bander, I even had a deer eat a captured adult bird out of one of my nets, leaving just an empty hole gummy with saliva (after that discovery, the deer were not welcome in the banding area).

White-tailed Deer

Yum, apple!

We’d be just coming into the fall rut about now, but it’s unlikely that this youngster will be participating. Though males are sexually mature at a year old, they must compete against mature males with full racks of antlers for the privilege to mate with available females. Even when there are many females in the population, usually only a handful of males will get to father the fawns. Sexual maturation of females varies and is dependent on population levels. In healthy populations, a female will usually breed in her second or possibly third autumn. Where populations are severely depressed, females may reach sexual maturity and mate in their first autumn, though this is unusual.

White-tailed Deer

Juicy apple!

I had to laugh at the following statement on Wikipedia: “Though human encounters are rare there are only an average of four cases of human casualties each year in the highly populated areas such as Minnesota, North and South Dakota, and Wisconsin. Usually, white-tailed deer will not approach a human unless it smells a bucks urine on the person.” Only four? I was astounded that there were even four! I don’t typically think of deer as aggressive animals. However, the second sentence is perhaps a clue to the circumstances – hunters carrying deer urine for the purpose of attracting bucks during rutting season might be injured in a case of mistaken identity. Hey, when your brain’s flooded with hormones, how clearly are you thinking?

White-tailed Deer

Delicious!

Recent news: Doe with antler

Deer in the news

We get two local papers here, the Frontenac News and the Frontenac Gazette. An interesting thing about rural and small communities that you don’t really get in larger cities is these community papers. Of course, the larger cities have their own papers, too, they’re just serving more people so they lose that intimacy, that sense of community. Instead of hearing about local birthday parties or shop owners, or the front page photo being about the Superhero Spirit Day at the local high school, you’re hearing about various crimes and politics and the financial market. It’s much more interesting to read the little community papers.

Even so, I don’t always read them all, so when I was crumpling up a sheet from the News to get the fire started a couple mornings ago an article I hadn’t seen caught my eye, mostly because of the photo, which was of a deer. The headline read, “Local hunters fell unusual catch”. The full article is in the image above, but the gist of it was these hunters had killed a deer that had a single antler, which was in velvet. The deer, it turned out, was a female, a doe. A story about a female deer sporting an antler, won’t see that in the Toronto papers.

The story notes that the hunters called the Ministry of Natural Resources “with two understandable queries: 1. Is this a safe animal to eat? and 2. Would the MNR be interested in it?”

Those weren’t the questions that I was expecting. The two that had sprung immediately to my mind were: 1. Why does this occur? and 2. How common is it? The latter question had been answered in the article (although the hunters hadn’t known that upon killing the doe, I don’t think) based, I gather, on the MNR’s website. But the first question is not touched upon in the story. Really, that’s the most interesting part about it all, in my opinion.

So to finish off the story, why does this occur? And how common is it? Sources disagree on the answer to the latter question, with Wikipedia saying 1 in 10,000 will have one or both antlers, an article from Penn State U suggests 1 in 1,000, the Minnesota Department of Natural Resources suggests that it can vary from one population to the next, usually between 1 in 1,000 to 6,000. The same page also mentions one study in Pennsylvania found the occurrence to be 1 doe in 3,500 antlered deer (so, 3,499 males and one female), and another in Alberta counted 8 antlered does in 517 does total (about 1 in 64, thought to be the result of unusual genetics in the area, or perhaps just a sampling bias).

The explanation of why this happens lies in the physiology of the antler itself. It all begins with testosterone, the hormone produced primarily by the male testes, but which is also found in females (usually at about 1/20th the concentration it is in males). Deer have bony “buttons”, called pedicels, on the frontal bones of their skull. In the spring, a surge of testosterone triggered by increasing daylight levels prompts the pedicels to start developing bony growths. Initially they are soft, covered in blood vessels, nerves and fuzzy skin, referred to as velvet. In late summer a second surge of testosterone causes the bone to harden, the blood vessels to die back, and the velvet to slough off. The male deer rub their antlers against trees and branches to “polish” them, and remove the velvet, and then they use these hardened growths to spar with each other during the rutting season in fall. Early in winter, in the weeks surrounding Christmastime, the testosterone levels start to subside, and a layer forms between the antler and pedicel. Eventually the layer loosens enough that the antler is rubbed off and dropped. In the spring the cycle begins again.

In the case of these unusual does, some trigger such as a hormonal imbalance caused by first pregnancy, tumours, or degeneration or malformation of the reproductive organs or adrenal glands, releases that surge of testosterone that prompts the pedicels to start forming the soft velvet antlers. However, the doe never receives that second surge that results in the velvet sloughing off, or the subsiding of the hormone from this high level that causes the antler to fall off, so she ends up carrying a permanent velvet antler(s). Many such does are reproductively functional and can and do bear young, though others may have malformed reproductive organs. Some of these “does” may actually be hermaphrodites with the female organs dominant, or gyandromorphs (one half of the animal has XY chromosomes, the other XX – that is, one half is male, the other female, sometimes split nice and evenly down the middle like this Rose-breasted Grosbeak). “Does” with polished antlers, where the velvet has fallen off, are more likely hermaphrodites with the male parts emphasized, cryptorchids (males with undescended testicles, “crypto” is Greek for hidden, and “orchid” Greek for testicle), or pseudohermaphrodites that externally resemble females but internally are male.

So there you go, the rest of the story that was left out of the article (I figure they must have just run out of room on the page…).

Other things in the woods

Creek

I probably ran off a good 150 photos while out with Dan and Raven at the park the other day. I would likely have taken more but for the fact that we were running out of time (constrained by the number of hours of daylight) and I eventually had to exercise some restraint in not stooping down to photograph something every 20 meters. Also in that we didn’t find the bog; if we had, that would’ve been another 50 photos just in itself. I’m beginning to run out of disk space on my computer, and it’s not a particularly small hard drive. That’s what a 10.1 megapixel camera does for you. I should start printing some of my photos up and selling them as posters, to take advantage of those 10.1 megapixels (since there isn’t much other need for them). I wonder if they’d actually sell.

I take lots of them with the intention of sharing their subject matter here on the blog. Of course, often they get buried as I turn to more interesting or more timely subjects and I never come back to them. But other photos are just simply landscape images that I found really eyecatching or said something to me. Many of these sit dormant, buried in the hard drive somewhere. Some I share here. The above (obviously) falls into the latter category. So many of the water bodies we encountered were reflecting the sky in the most gorgeous, rich, deep sapphire blues. I really couldn’t capture it with the camera, at least not the way my eye saw it and not without any fancy filters or equipment. But I thought this one came close.

Ribbon Snake

We came across this snake on the path. It’s an Eastern Ribbon Snake, Thamnophis sauritus, and can be separated from the similar-looking garter snake by the presence of an additional yellow line along the side (that is, the garter snake has a yellow dorsal line and a yellow belly, while the ribbon snake has a yellow dorsal line, a yellow side line, and a yellow belly). It’s also a slimmer, more delicate-looking snake. I actually nearly stepped on it, only noticed it as it rapidly slithered out of my way into the leaves at the side of the trail. I called to Dan to point it out, and he managed to snag it for a photo. It was fierce, and actually struck out a couple times toward the camera (seemed to pay no attention to Dan, interestingly). It also stunk like a sonuvagun. Most snakes produce a very smelly musk from glands in their vent (the combined reproduction and elimination orifice that reptiles, amphibians and birds all have) that serves to discourage predators. Sure discouraged us, more than the open mouth. Dan put it down quickly once the photo was taken.

Garter snake

Not much further along was this Common Garter Snake, Thamnophis sirtalis. I was rather surprised to encounter one snake on the trail, much less two, given the lateness of the season. However, the weather was nice, nearly 15 C (60 F) and they probably came out for some last filling up before hibernating for the winter. They were sunbathing on the warm leaves when we came across them, and while the ribbon snake scurried off, the garter snake didn’t move at all. Garter and ribbon snakes are closely related, members of the same genus. They’re among the most common snakes, found in suburban gardens and yards as well as the untamed wilds of rural areas.

Pileated Woodpecker excavations

Aside from the two snakes, and a handful of chickadees, Brown Creepers, and a couple other birds, not very many animals were observed. However, they were in evidence from the signs they left behind. This birch stump was at the side of the trail, and looked like it had been freshly worked on within the last couple days. It’s the handiwork (billiwork?) of a Pileated Woodpecker looking for ants or grubs. The size of the excavation, plus the neatness of the edges, identify the species responsible, since other woodpeckers will make smaller excavations without much mess, and larger animals, such as raccoons, will make messier holes. I thought it was neat how the shards of wood cascaded down from the excavation like a waterfall spreading out into a pool at the base of the stump.

Deer browse scraping

Another animal that had left some signs of its presence behind was White-tailed Deer, Odocoileus virginianus. We found a few spots with droppings, but also quite a number of these scrapings in the ground. The leaves had been cleared away from the area as the deer looked for things to eat, and the primary reason I knew it was deer and not something else was the presence of the cleft-hoof tracks in the dirt. Deer are known to eat acorns and beechnuts as part of their fall and winter diet, and since the predominant trees in the area were maple, oak and beech, these were abundant in this forest. I suspect they were clearing the leaves in search of acorns, now that most plants have lost their green vegetation.

Brown bear digging and scat?

And finally, on our way back, as we crossed through a grove of pine trees, we came across a large area of ground that had been dug up as the animal searched for food. In a couple spots, in the middle of the excavation, were some piles of loose gray scat. It’s amazing how much you can tell from scat. It’s often very species-specific in its particular characteristics. In the photo above Dan is poking at it with a stick to examine its consistency and contents, both important in determining from what animal the scat came from. There aren’t too many species that will actually dig up the earth like this, as opposed to just scrape at the surface like the deer did. Two of the possible critters, skunk and raccoon, have tight, compact scat. The other suspect tends to have looser dung, as this was, and a varied diet. This looked like it was full of crushed mussel shells (though we didn’t look too too closely to know definitively). After examining the evidence, we thought this was probably the work of a Black Bear, Ursus americanus. Bears are omnivores, eating a wide variety of foods, from berries, to grubs in the soil, to mussels at the lake shore.

So many things to see! One more post tomorrow from that hike, and then on to other things.