Trowbridge shrew

I mistook this for a mouse, but on the computer screen at home it was clear that the ears were too small.

There are two species of shrews in the northern Sierra Nevada that sport brown summer coats and bi-colored tails.

The Wandering or Vagrant shrew (Sorex vagrans) prefers open meadows, while Trowbridge's shrew (Sorex trowbridgii) is found in conifer and mixed deciduous forests.

This hollow tree is in an extensive stand of red fir; so I am assuming we are looking at Trowbridge's shrew.

Shrews don't stay put, and they tend to be found in microhabitats overlooked by most camera trappers.

It's a special occasion when I get a photo of one.

The bear comes back

That hollow red fir in Sierra County was an enchanting place, and I wasn't ready to pull the camera after just one month.

A natural shelter like that is such an attraction to wildlife that you never know what's going to stick its head in the door.

The yearling bear visited on four more occasions, giving us a better selection of portraits, but on the second visit it knocked the camera ajar.

We might have missed quite a show if it had remained pointing at the entrance, but by a stroke of good luck it was still upright and aimed at a pile of carpenter ant frass.

Next time you'll see an incidental visitor, after that an unabashed show of sensuality.

Peeping in

The hollow belly of the red fir seems like a safe and snuggly place.  

It's quiet in there and it's dry, even though frass rains down 24/7 from the gallery of wood ants above.  

Bob's observation that "the cavity . . . looks like a bear den" was right on the money. 

Ten hours after we left the scene a bear peeked into the cavity.

In the next week the opening framed a robin several times,

and a chipmunk made a brief visit.

Then a small bear paid a visit,

and toppled the camera.

The camera took pictures of wood ants on thr floor of the den until we came back and reset it.

If I had a time lapse camera with 5 months of battery power, this would be a fine place to monitor a sleeping bear.

[If you like this sort of thing, be sure to check Random Truth's bear-in-the-log pictures.]

Views from within

The whitefooted mouse came and went most of the night, but just before dawn a raccoon made its appearance.



It went all the way to the end and ate the smoked herring. I got twenty butt shots.



Then it turned around, but the camera was too slow for a mugshot.



I believe these guys have a powerful thirst today. That smoked herring is heavily salted.

A Jonah log

At last, I found what I've been looking for -- a Jonah log, a log for camera trapping from within. It's a fallen snag with a cavity about 12 inches wide and 6 feet long. No need for chain sawing. There's a large opening big enough for the camera trap, and a small opening to create a draft over the bait -- in this case, smoked herring. True, it's a bit far from home here in northern Virginia, but good Jonah logs are hard to find.



I hope the county park authorities don't mind some cosmetic adjustments. The cavity was a basin, a nasty microhabitat for disease vectors, and it seriously needed drainage. Plus, I don't need any surprises like finding a camera floating in punk water.



Then I juryrigged a camera mount (not many supplies here at my daughter and son-in-law's).



The walk test was impossible. I couldn't see if the sensor was detecting my hand, so I recruited the redhead. While she looked for the flash in the big opening I imitated a vet giving a rectal exam to a cow.



I am not promising anything from this Jonah log. There are just a few days left before we head home, but until then I'll be checking it daily.

When a snag is not a home

I eyed this black oak with growing interest for two years. Those two knot holes, about 30 feet up, looked like they were made for owls.

Three weeks ago I got around to staking it out with a camera trap. I lashed the telescoping pole to a fir sapling, and raised the camera to the cavities.



Looks can be deceiving. I didn't even get a picture of a squirrel.

It looks as though the upper hole collects water which trickels into the lower cavity where it overflows. Somehow I failed to notice this.

No self respecting squirrel or owl would have anything to do with such a shabby place. Which reminds me, I have to repair the roof this summer.

Magic squirrel mulch

An incense cedar fell across the flume during the last storm. Evidently the tree had been injured when it reached a height of about 40 ft.



The original shoot is the gray stub on the left. It died back from the damage, and eventually became a bird's nest cavity.

Two new shoots replaced it and grew into the two logs you see laying across the flume. These forked shoots were off center, and as they grew they placed an increasing strain on the trunk. This year they strained the trunk to the breaking point. Heavy winds were all it took to snap the trunk.



The trunk was hollow, but squirrels had packed it with cedar bark stuffing. It smelled good, and I started to dig it out like a terrier in a rat hole.

"I wouldn't do that", warned the redhead, "it could have fleas and all kinds of things.

"My God, there's squirrel hair in it! Tail hair!" I exclaimed. "Why this is a multi-generational squirrel nest!"

"Remember when your house had the flea infestation and your parents threw out your bird nest collection?"

"That was different," I answered. "This is self-sanitizing nest material filled with terpenes and secondary compounds. Just smell it. It's wonderful." The redhead backed up a step.

"C'mon!" I pleaded. "It smells just like cedar pencils."



Finding a fallen tree can be a cheap thrill for a biologist, especially one with cabin fever.

As we walked home I hatched a plan.

Three days later I returned to the scene and packed three grocery bags with magic squirrel mulch. It looks great around the camellias. The redhead hasn't noticed yet. When she does, I'm going to tell her, "It's special. You can't buy it at the garden center".

Tidak ada, Tuan

"Tidak ada, Tuan." That's Bahasa Indonesia for "There was nothing, Sir". In context, it meant, "No luck today" or "Not a damn thing".

Those were the words of Jaffa, the empty-handed eel fisherman as he passed our riverside camp in northern Sulawesi. He laughed cheerfully about his bad luck. The joke was on him. (May he still ply the waters with good cheer and better luck.)

It was a "Tidak ada" day when I checked the cam at the snag with possibilities. There were 70 pictures, and nearly all of them were dim images of deer mice putzing about in the bottom of the snag. I didn't laugh at my bad luck, but I was grateful that the camera set worked.



The good news was that there were three fuzzy images of what appeared to be a wood rat and a spotted skunk. They were obviously squeezing past the camera when it fired.

The peanut butter had barely been touched. I need to think about another bait, and a better way to secure the camera in place -- like lag bolts and wire. Next time.

I cranked up the flash power, and adjusted the camera's position. I'll let it run another week.

I do have some of Jaffa's patience, but I haven't reached the point where I see the humor in going home empty handed.

A snag with possibilities

I'm always on the lookout for good snags. The goal is butt-rotted snags (with hollows at their bases), snags with cavities and nest holes higher up the trunk, or snags with broken tops. It's a old mammalogists' habit. You never know what you're going to find inside a good snag.

In my old collecting days there was always that cheap thrill of anticipation when you fired up the bee smoker and blew smoke in the hole. Back off if bees and wasps start to evacuate. Keep puffing if you hear something stirring inside.

When frass and punk wood start to fall get the net over the hole and brace yourself. Whatever is in there, it's going to come out in a hurry and with a bad attitude. It may also want to eat your face.

If you don't have a bee smoker, a human smoker will do in a pinch, theoretically.

We got smoking Jim Murphy to light up and blow smoke in a hole in a sacred thabye (Eugenia) tree in Burma. Jim's a herpetologist, and he became terribly excited when we told him a big snake had gone in the hole. He really liked the idea, so we passed him lit cigarettes and coaxed him to blow faster as the locals stood by and watched in wonderment. The snake never came out, and Jim almost passed out. He didn't need a cigarette the rest of the day. On second thought, I think it's better to use a bee smoker.

Nowadays you might get an idea of what's inside a snag by sticking your digital camera in the hole and snapping a picture. (There are also some high priced video gadgets for sale that do the same thing and even more.) If you decide to try this, bring a chain saw or a piece of strong nylon line. If you drop the camera, you can saw the tree down, but it's easier to fish the camera out if you've tied the line to it.

I've been looking for snags where I can get an inside view of what creatures come and go. Below you can see the inside of a promising snag not far from my house. It has two openings, one on top, and one on the side. I perched on the ladder to take this picture looking down the hole on top. The pale line you see in the photo is a stick marking the hole on the side.



The tree probably snapped off in a wind storm, and the resulting hole on top is shaped like a rounded triangle -- just big enough to accommodate the triangular arrangement of the camera trap's lens, flash, and sensor. I fastened the camera trap with a bungie cord and adjusted its angle with an aluminum rod strapped to the trunk.



The hole on the side of the snag is big enough for a squirrel or small owl. I smeared peanut butter inside the entrance and on the side walls. As I was doing this the camera snapped a couple of pictures. That's good. I'll wait a week to see if any squirrels go for the bait.

Upscale California housing

Does a deer mouse really need this much space?

When I discovered the den last week, there were auspicious signs that the tenant was larger than a mouse or rat. For one thing, there were no spider webs across the entrance. Something big and furry had been swabbing it out. And there was plenty of bunk space upstairs in the apartment. I had high hopes the occupant would be an opossum or a raccoon (which for some strange reason I rarely photograph here), or maybe a spotted skunk.

I staked it out for four days, but the place was so promising that I paid a visit after the second night.

"Well, I'll be . . ." Something had knocked the camera askew.



And not only that . . . it had bitten off the camera trap's "eyebrow" (a PVC ring hot-glued to the case to protect the lens window from rain). Fortunately, none of the three windows was popped or broken.

The anticipation was killing me. Was I about to find an image of a beady ursine eye peering malevolently into the lens?

I opened the camera, flipped the switch to view mode and clicked through the images . . . deer mouse, deer mouse, blank, deer mouse, blank, deer mouse, deer mouse. . . Get the picture? My spirits were rapidly deflating. Then came the last picture.



This was the only visitor who could fill the den, but Ole Stripey was only passing through and had only paused for a sniff. I had to ask myself--was this skunk my camera's abuser? It seemed so out of character. Surely a skunk wouldn't take on the camera with its teeth. I don't think it could have even reached it.

When I got home I found two sharp indentations, 22.6mm apart (as measured with a caliper) in the base of the PVC ring. Now I ask you, can someone tell me the distance between the canines of a striped skunk? A raccoon? (My skull collection is still in a box somewhere in the garage.)

Anyway, two more days yielded more pictures of (yawn) Peromyscus -- both adults and blue-coated juveniles. The cushy upscale den was only a flop house for deer mice, and I am left with an unsolved puzzle.

The snag of fleeting promise

The snag looks promising, wouldnt you agree? As soon as I saw it I thought of small owls or large woodpeckers. So the next day I trundled down the hill with my rucksack filled with sections of a mounting pole, nylon cord, camera, and tool kit. I staked the camera about 6 feet away from the cavity so the sensor would monitor a large area.

It rained that night, but I got one picture. I zoomed in on the LCD, and Whooppeee -- it was a saw-what owl! A new subject to camera trap.



The image was trashed by a drop of water, but I was buoyed by my discovery and moved into action. "Don't bother changing memory sticks", I told myself. "Be patient. In one more day you can savor a whole series of owl shots."

I moved the camera closer to the cavity and messed around for a half hour getting the sensor perfecty aligned. I was feeling the thrill of the camera trapper's chase. Envision the scenario, decide on the optimal angle and distance, double check all the settings, then study the camera's position from all the angles. When I was finished I marched up the hill and felt nice ("like sugar and spice"). The happy prospect of finding a new species does that to you.

The next afternoon I lowered the cam and found . . . WAAHHH! -- 141 pictures! I clicked through a dozen pics of the snag, but the absence of owls didn't worry me. I knew that the nesting screech owls often come and go before the shutter releases--which accounts for empty frames. Then I got home, and found only three images of an animal.



The snag was a high rise for deer mice. Apparently the opening of the nest cavity connected to an "elevator shaft" all the way to the ground. The mice climbed past the nest hole all night long, and triggered the camera on average every minute and 18 seconds.

I consoled myself with the good fortune of getting one picture of a saw-whet owl, and pulled down the camera set. A half hour later I found another promising snag -- a butt-rotted oak with a large den opening at the base. You'll be hearing from me soon.

Recluse in the snag

Three days ago at 6:13 PM a squirrel climbed down the snag and aroused the resident screech owl (who looked pretty scary to me). During the next two nights the owl took 143 pictures of its own comings and goings. Or should I say owls? If there is a pair, I can’t tell them apart.

The cavity is in a black oak and looked unused. So I was prepared for disappointment this afternoon when I went to check the camera. For nearly two weeks I have been using a new toy -- a telescoping fiberglass pole -- to raise the camera up to the level of tree cavities. This tree was second choice.

I expected a bonanza of pictures from my first choice -- a much-pecked flicker-sized cavity about 25 feet up. It had all the signs of occupancy, except the presence of a bird. The edge of the cavity had been chipped away and enlarged recently.

It was a bear of a job getting the camera into position, because when it is 25 feet overhead you can’t really see exactly where the camera's sensor is in relation to the cavity. From one angle they look like they are face to face. Then you move uphill to confirm it, and the camera looks too low. So you make adjustments and check again. And again. The other problem is pole-wobble. Even when anchored with guy lines, the slightest breeze wobbles the pole, which fools the sensor, and the camera goes wild taking pictures of moving vegetation.

After failing with a cavity that had "active nest" written all over it, I settled for one that was 12 feet up.



It looked abandoned, but I got a nice surprise. There were many shots of the little guy checking out the camera and the scenery.



And then there were shots of it clinging to the entrance.



And (whoohoo!) I got three pictures of the owl in flight.



Now to improve the set-up so I can get that picture of mini-raptor with limp deer mouse in talons.

Beautiful snags I have known

I've been attracted to snags ever since I was a kid. Initially my attraction was to the California acorn woodpeckers in the snags. They carried on noisily in their acorn granaries high in a few dead Douglas firs along the San Lorenzo River. That was near the town of Ben Lomond in the Santa Cruz Mountains, where the woodpeckers also stuffed acorns into the power poles. When the neighborhood kids came down the gravel road in the afternoon, Mr. Dickenson slowly leaned out his window and gazed up at the gathering flock of woodpeckers. He was an introverted show-off and woodpecker trainer, who moved in slow motion and rarely acknowledged our presence. We stood in wonderment as he drew back on his Whammo slingshot and released a ball of wonder bread sky high. Immediately the woodpeckers launched themselves upward in pursuit of the soaring bread ball, but only one would snatch it at the arc of its trajectory. The show continued till all were fed.

Eventually I became less animal-centric and started to appreciate snags for themselves--as dead wood, micro-habitat, nesting areas, subjects for post-mortem tree analysis, and of course, places to set camera traps. A U.S. Forest Service entomologist named Torolf ("Torgy") Torgerson summed up the importance of snags with Scandinavian terseness: "…if you want live things, you need dead trees." Broadly defined then, snags are standing dead trees, or living trees with dead wood, cavities, hollow trunks.

The most interesting snags around here are incense cedar. They don’t seem to form cavities readily, but when they die they stand in silent dignity like wooden Indians. There was a burn here many years ago when cedars were much more common on the upper slopes. Some enormous charred stumps and a few old upright veterans still remain. When the snags finally crash, they lie around for many more years. On the north slopes they grow a coat of moss, but eventually they return to the soil. Knots and sapwood are last to go. I can understand the persistence of knots; they are very dense and resinous. But why the sapwood lasts so long is beyond me. It readily decays in ponderosa pines; why not cedar? Even before the heartwood has crumbled away, great boards of sap wood unfurl and fall to the ground. Habitat for creepy-crawlies.



This lovely snag (the same one at the top of the page), has a 7 foot circumference and stands about 50 feet high. The heartwood has already crumbled away leaving a skirt of sapwood.



The knots of former limbs anchor the sapwood skirt to the softer underlying wood, but it's a tenuous connection. The protected surface underneath could shelter bats, but on this tree it's too close to the ground, and a snake could reach them with little effort. But the space is being used -- mice and squirrels have tucked acorns here and there.



So how exactly do beautiful green trees became gnarly gray snags? Fire and root disease kill trees outright, but trees dying of these causes don't become hollow. And root-diseased snags don't remain standing for long. To get cavities you need injury from boring insects, lightning strikes, or mechanical damage and infection by wood-digesting heart-rot fungus. When you see a conk of fungus on a living tree, you know it is infected.



Not all tree species get cavities from heart rot fungus. Only certain ones are cavity prone. In northeastern Oregon for example, most hollow trees are grand fir and western larch. These trees provide nesting sites for cavity nesting birds. Here in the Sierra Nevada there are nearly 2 dozen species of cavity nesting birds, not to mention northern flying squirrels, western gray squirrels, red squirrels, bushy-tailed woodrats, several species of bats, martens, raccoons, and black bears. To an extent they all owe their livelihood to heart-rot fungi. The black bear also benefits from root fungi, which spread decay into the tree base. I guess foresters have a sense a humor, or they wouldn't call this condition butt rot. The biggest black bears benefit from butt rot, which makes splendid dens in big old trees.


References
Bull, E.L., C.G.Roberts, and T.R. Torgerson. 1997. Trees and logs important to wildlife in the interior Columbia River Basin. General Technical Report PNW-GTR-391, Pacific Northwest Research Station, U.S. Department of Agriculture.

Meyer, M.D. D.A. Kelt,and M.P.North. 2005. Nest trees of northern flying squirrels in the Sierra Nevada. Journal of Mammalogy 86(2):275-280.

Raphael, M.G. and M. White. 1984. Use of snags by cavity-nesting birds in the Sierra Nevada. Wildlife Monographs No. 86:1-66.