Of shrews and owls

What: On Saturday Nathan and I went for a wander in Centennial Woods. We were exploring the lower stretches of Centennial Brook in Fox Marsh when we heard some crows making a ruckus to our East. We decided to track down the birds and see what the fuss was all about. Turns out the crows were harassing a barred owl that seemed more interested in napping than paying attention to the crows. After about 15 minutes the crows left the owl at peace. It was interesting to watch the owl over then next 45 minutes or so because any time a crow flew nearby it would caw, just to remind the owl they knew it was there. We walked back to my house to get better binoculars and my camera and the owl was still there by the time we got back. I snapped a couple of pictures of the owl perched near the top of an old white pine.

Short-tailed shrew skull found in barred owl pellet

Ecological notes: I've found a few owl pellets recently, (coincidentally?) all at the base of old white pines. The last one I pried apart was on the small end of pellets, but still had one vole and one shrew skull in it. The shrew skull was beautiful - I've always been drawn to the purple on the enamel of the teeth (as in rodents, the color is due to an iron pigment). Rodents have iron pigments on their incisors and softer exposed dentine (our dentine is hidden beneath our enamel) to maintain a sharp chisel edge. Anemic rats have been found to lack the pigmentation on their incisors! Older scientific articles speculated that the coloration could have been used as a signal (making the teeth visible when the animal grins aggressively). I doubt that, as white is equally visible. In shrews, it could signal health (redder teeth means more virility, as red feathers indicate virility in male cardinals, flamingos, etc).

Challenge: Find its eyes (or ears)!

I'd put more money on it being an architectural thing, increasing the strength of the teeth. Shrews are insectivores (in the order Insectivora, along with moles, neither of which are related to rodents; rodents, in fact, are closer to humans than shrews; shrews are closer to elephants than rodents like voles). Their diet consists primarily of arthropods (those six-legged bugs), which have hard shells. If you ate nothing but crab and had to chew through their shells with your teeth you could imagine your teeth would wear down pretty quickly. Reinforced teeth help their teeth last longer, though most shrews don't live past a year. Mira also found a short-tailed shrew (Blarina brevicauda) in Centennial Woods last week, which would be about the 6th this winter that showed no outward sign of any trauma.

Right front of short-tailed shrew

Rear feet of short-tailed shrew

Some observations we made about the shrew:

• They have super short hair that rubs well both forward and back (possibly for entering unknown tunnels in search of prey)
• They have large ear openings, but the external ear itself is super small
• Their eyes are all but absent
• Their whiskers are very prominent up the snout
• The snout seemed to have the same reddish purple color that the teeth have
• Their claws were exceptionally long

Where: Centennial Woods

Other notes: Almost exactly a year ago I spotted a barred owl in the same spot in the same way. I had actually followed the crows to a nearby spot where they were mobbing a red-tailed hawk.

Possum and more feet

Right front

Left rear

What: Brooke alerted me to a roadkill opossum (Didelphis virginiana) on East Ave the other day that I picked up. I like to poke fun at these bizarre critters, since they're one of the most retched creatures we have. They amble in a dopey, almost drunken way, are often drooling, and are frequently the victims of frostbite, which reeks havoc on their ears and tails. I once watched a possum lick my fence for about 15 minutes. I got close enough to touch it, but not close enough to have any idea of what it was licking. They're certainly a different kind of beast.

Frost bite on ear

Fun facts about the Virginia Opossum:

• Possums have a super short life span (a 2 year old possum is ancient)
• They have 50 teeth (dental formula: 5134/4134)
• Possums don't "play" dead but actually become catatonic. It's an involuntary response, the crescendo of which is the expulsion of a foul smelling liquid from their scent glands. I'd assume that this deters any predator from wanting anything to do with eating the animal (it also starts drooling, will urinate and defecate as well as lower its temperature and heart rate). 
• They only have awn hair, which explains the raggedy look of their coat (somewhere between the insulative down hairs and the coloration hairs we collectively call the pelt and individually the guard hairs)
• Only the females have pouches (and they're super small)
• Possums frequently get frostbite here in Vermont. They're at the northern most extent of their range and have naked tails/ears. Like cardinals, they have moved their range north following urban centers of people.
• Males have a scent gland on the chest that gives the fur in that spot a gross yellow color
• They are not winter mammals, and can lose almost half their body weight during the winter
• Sperm is paired and doesn't swim straight if single
• They're essentially immune to snake bites
• They're total scavengers (which might be why I have such an affinity for them) and apparently have a rapacious appetite for calcium so frequently eat road kill skeletons
• They supposedly even will kill rats, but mostly they scavenger for invertebrates and carrion
• They have a very very slow metabolism (unlike shrews) and move much slower than most animals their size

Frost bite on tail

Ecological notes: The frostbite they frequently get doesn't matter all that much, nor is their much selective pressure pushing them to adapt to the winter since they live such short live (rarely living more than one full winter). They are continually pushing their range northward. Young possums can hang by their tails, but adults can't.

Where: East Ave

Other notes: Opossum comes from the Algonquian word "opassum" which translates roughly to "white animal". The word was first used in 1608 by Capt. John Smith. His description of "possums" (the 'o' was dropped in writings as early as 1613), is simple and alludes to the oddball-ness of the creature: "An Opassom hath an head like a Swine, and a taile like a Rat, and is of the bignes of a Cat. Under her belly she hath a bagge, wherein shee lodgeth, carrieth, and sucketh her young."

Other posts with photos of animal feet in them:

• Raccoon
• Red squirrel
• Gray squirrel
• Mink

The Continuing Saga of Squirrels and Walnuts

*** Starting this week my UVM students will be posting occasionally in response to the prompt: Find something in the woods that you've never seen before and figure out what its story is. So look for that!

What: Last week Clay and I found a dead gray squirrel (Sciurus carolinensis) on the sidewalk. It was a pretty good mystery as to how the squirrel had died. I skinned it with my Crow's Path kids and before we did the autopsy we couldn't detect any broken bones from getting hit by a car (plus it was about 10' from the road). The squirrel was a full grown male (just about the most enormous squirrel I've seen), and we thought maybe it could have eaten poison from a nearby house, fallen out of a tree, got hit by a bike or chomped by a cat/dog. We couldn't find any evidence of blunt trauma from getting hit by something, but when we pulled the skin up above the neck we could finally see two chomp marks that hadn't pierced the skin (so no external blood) but were most likely what killed this little critter.

You can notice in the two photos below the difference between the rear (left) and the front feet (right). The difference in color is due to the constant assault of the squirrels on the walnuts (see my previous post on how it stains their face and paws). I love looking up close at squirrels to see all the little differences between individuals, and this little guy, with a lone black chin hair popping out, was no exception. It also had orange staining its whole belly, probably from eating walnuts and then grooming its belly (around its crotch was particularly orange, which was amusing).

Ecological notes: With the kids we noted that the rear foot was flexible in almost all directions and could rotate just about 180 degrees. I was telling the kids that the squirrels will hanging from a tree hanging down with their feet rotated back behind them. I've also noticed that when they leap to a branch they rotate their feet so that they're hanging below their body and the bottoms are facing the direction they're going. As they hit the branch their rotated feet catch their body and grip onto the branch as they then rotate around to face forward and propel them in their next jump. Amazing! Another thing to note is that animals have larger feet where they hold most of their weight. Gray squirrels hold most their weight in their butts, so have larger rear feet. Same with raccoons, possums, beavers, etc. Dogs (think about pitbulls here) have larger front feet to support their broad chests and big torsos.

Where: Burlington