About Me

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Native Californian, biologist, wildlife conservation consultant, retired Smithsonian scientist, father of two daughters, grandfather of 4 small primates. INTJ. Believes nature is infinitely more interesting than shopping malls. Born 100 years too late.

Wednesday, February 28, 2007

Camera trap pioneers: O.P.Pearson

Game trails have always interested naturalists, because they tell us where wild animals move and how they use their habitat. Trails come in all sizes, are usually "engineered" for energetic economy, and are most pronounced where activity is concentrated--near feeding areas, water, or mineral licks. Climb a tree or hide near a game trail, and sooner or later you will see who uses it.

In the 1950s, Dr. Oliver Pearson of the University of California embarked on a traffic survey of mouse runways on his property in Orinda, California. Professor Pearson was a distinguished and particularly inventive scientist who studied mammals and birds. His interests ranged from taxonomy to physiological ecology and predation. He was also a pioneer in the use of camera traps.

Pearson wanted to know what goes on in the microcosm of mouse runways. To a mouse, a patch of weeds or a grassy field is like a jungle, and species like meadow mice bushwhack and maintain their own runways with their teeth. In a clear runway they can zip along at a brisk clip and tend to their daily business. Harvest mice enjoy the labors of their larger neighbors.

Pearson's property harbored populations of meadow voles and harvest mice only 50 feet from the house, and the epicenter of his study was a 20 x 20' weed patch with a brush pile in the middle. Could a professor of mammalogy ask for anything more?

He used two 16mm movie cameras in tandem with weather stations to survey the traffic. The camera shutter was electrically activated whenever a mouse or even a large insect passed the camera lens. He used two trigger mechanisms with equal success, a treadle and a photoelectric cell.

The cameras were synchronized with electronic flash units. Nowadays we can snoop on sensitive species using infra-red cameras. To avoid frightening the mice, Pearson masked the flash with 18 layers of red cellophane, and noted that "a muffled clunk made by the mechanism seemed not to alarm the mice unduly."

Powered with alternating current, the cameras ran day and night, but there was a problem with differential exposure. Daytime pictures were overexposed, because the shutter was slower than 1/30th of a second and the f-stop was adjusted for night. Again the solution was red cellophane, this time over the camera's lens. The camera units were sheltered in glass-fronted housings. Overhanging eaves and a blackened light bulb counteracted the effects of rain and dew.

Pearson positioned a camera unit on one side of a mouse runway. On the other side, and framed within the camera's view, were the instruments of a miniature weather station: a dial thermometer, a hygrometer, a ruler, and an electric clock with a sweep second hand. Thus, whenever a creature took its own portrait it also recorded its body length, the time, and a weather report. Since he live-trapped the mice and gave them distinctive "haircuts" he could identify many of them individually.

Not long after he deployed the equipment, the neighbor's Siamese cat discovered that the camera housings were superb perches for mousing. He solved the problem by fencing the weed patch. Then a slender salamander electrocuted itself while short-circuiting the treadle. Delusional song sparrows were another problem. They wasted a lot of film shadow boxing their own reflections on the weather station window. Curiously, one bird side-stepped an oncoming meadow mouse, a gesture of road etiquette rarely seen on California highways.

In nineteen months of operation (111 recorder weeks) the camera traps generated 8,495 photographs. In other words, weed-patch wildlife made an average of 11 passages per day. The professor noted that, "A patient, non-selective predator waiting for a single catch at runways such as these could expect, theoretically, a reward each 2.2 hours." The cameras mined enough information for three scholarly articles.

Pearson's first paper on the traffic survey contains the information of most interest to camera trappers. I'll go out on a limb here, and state my belief that the results also apply to larger mammals, especially other herbivores like deer.

His "pleasant surprise" was that 26 species of animals, from weasels to snakes and mole crickets--made use of the runways. He never saw three of these species within at least a mile of the study area, proving that camera traps often disclose nature's little secrets. Ironically, he never photographed three other species he commonly saw within 100 feet of the recorders! The take home message here is that placement of camera traps is critical.

Though two species of mice used the runways, Pearson's camera traps revealed that meadow mice were the "public works custodians". When meadow mice stopped using a runway, weeds and seedlings quickly filled them in. Another curious finding was that mice apparently used runways selectively even though nearby runways seemed equally suitable.

Pearson's camera trap studies of rodent ecology are still among the most elegant and detailed studies of their kind. The work also seemed to stimulate Pearson's interest in predator-prey relations, for he went on to study predation of mice in Tilden Park not far from the UC campus. During the next twenty years a smattering of biologists, including your's truly used homemade camera traps for wildlife studies and surveys. Then in the 1980s camera traps became commercially available, and wildlife biologists developed camera-trap-fever.

Often we don't discover common interests till it's too late. This camera trap codger wishes he had mustered the courage earlier in his career to ask Pearson about his camera trapping days. Many times I saw the professor at meetings of the American Society of Mammalogists, but stood speechless and in awe. I guess we are a lot like meadow mice, politely passing each other through the runway of life. Mice and men are alike that way.

Acknowledgement: My appreciation to the Allen Press for permission to reproduce the plate from Pearson's 1959 paper, and to Kathleen Berge of the California Academy of Sciences for scanning it.

Osterberg, D.M. 1962. Activity of small mammals as recorded by a photographic device. Journal of Mammalogy, 43:219-229.

Pearson, O.P. 1959. A traffic survey of Microtus-Reithrodontomys runways. Journal of Mammalogy., 40:169-180.

Pearson, O.P. 1960. Habits of Microtus californicus revealed by automatic photograph records. Ecological Monographs, 30:231-249.

Pearson, O.P. 1960. Habits of harvest mice revealed by automatic photographic recorders. Journal of Mammalogy, 41(1):58-74.

Sunday, February 25, 2007

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.

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.

Friday, February 23, 2007

Escape, recapture, deportation.

It seemed obvious now that the mouse just didn't feel comfortable about squeezing into the Victor mouse trap. I suggested we try the harmless Howard gopher trap, developed by Howdy Howard at UC Davis for studies of pocket gopher ecology. I had a couple in the garage.

It was a triumphant moment the next morning when Richard called to announce that the mouse was in the trap. The squatter was an adult female deer mouse.

One manifestation of Richard's emergence as a field biologist was his wish to mark the mouse. This was in response to my warning about the homing abilities of mice. He wanted to mark its fur with a spot of fingernail polish.

I bagged the mouse without a hitch, gently pinned her, and held her by the nape while Richard dabbed a little nail polish between the silky ears. Then he passed me a half-gallon plastic jar, and I made the second transfer.

However my half turn to the jar's lid was a costly error. A moment later the lid came off and the jar dropped to the workbench. Miss Mousie made her break. She dashed across the bench, went over the edge like a trooper, and disappeared into the cabinets on the far end of the shop. An embarrassing moment.

"Now look what you've done", said Richard like Oliver Hardy.

"I think she might be in the family way, too," I said.

Richard responded, "Oh no, I hope not."

She stayed away the next night, but two nights later she was again in the trap awaiting deportation down the road.

Thursday, February 22, 2007

Building a better mousetrap

Last week neighbor Richard asked to borrow a camera trap. An illegal immigrant had taken up residence in his shop. It's droppings were on the work bench, and scattered here and there were bits of insulation. The little squatter was obviously building a first class nest. Though a man of uncommon generosity and hospitality, Richard draws the line at mice in the shop and gophers in the garden. He planned to trap the "wee sleekit mousie" and release it outdoors, but first he wanted to photograph it with my camera trap.

In view of the embarrassing number of times Richard has helped me repair things around the house, I was pleased for a change to be able to offer a lending hand. Truth be told, many biologists are a bit challenged when it comes to practical skills. When somebody like my neighbor -- who can fix and make anything -- wants to tap into your impractical skills and useless knowledge, well it’s a tremendous boost to the ego.

I took the camera trap and sunflower seeds to his shop that afternoon.
"Tonight I just want to get his picture," he said popping a peanut into his mouth.
"Okay, we'll pre-bait the area with peanuts", said I. "We'll leave the sunflower seeds in the trap--they love sunflower seeds--and when we set the trap tomorrow he'll be more than ready for them."
Like a couple of doddering Hollywood directors we arranged the props on the work bench into a mouse-friendly studio.

Richard called me on the phone the next morning--the mouse (a deer mouse) made a brief cameo appearance.

As planned, Richard set the trap that afternoon. The next morning the seeds were gone, but the trap was still open. The mouse had entered the trap several times and eaten the sunflower seeds with impunity.

And that wasn't all. It had jumped in and out of a 5-gallon plastic bucket to get the peanuts at the bottom!

"Now that's quite a feat, I remarked.
Richard took his measuring tape to the bucket, "14 inches high".
"Let's say the mouse is 4 inches long," I mused.
Richard followed through, "He's jumping three and half times his length."

Then he turned to the Victor live trap.
"I don't like this trap. It's too short!"
"This is a Victor live trap, Richard. Victor's been making mousetraps for over 100 years. They're experts in an ancient craft!"
"It's too short", he insisted. "I'm going to cut off the back and hot glue an extension. Then I'm going to move the fulcrum back. That way he has to go further in. This trap's too short!"

And that's exactly what he did.

I emailed him the next morning: "What's the score on the mouse trapping? Any pics last night? Do you need sunflower seed? Batteries? Lemme know."

Richard: "Well, he came back last evening but wouldn't go into the trap with the revisions. The batteries went dead in the camera and I didn't get many pictures."

Chris: "You're hooked! Hah hah! I'll give you a couple of rechargeables in exchange for the dead ones. (We forgot to change them). We should try a different trap too. You need to design the Chaddock Smart-Mouse trap. See you soon."

As a mouse hunter and camera trapper I found Richard's determination highly amusing. He normally reserved this kind of enthusiasm for his various mechanical engineering projects around the house. He was getting hooked. Maybe not hopelessly hooked, like me. But hooked nonetheless.

"You won’t believe it!" I told my wife.
"Believe what?"
"Richard is totally into trapping the mouse, and is designing new mousetraps. He even wants me to make him a camera trap!"
She paused thoughtfully, and said, "His poor wife."

(To be continued)

Sunday, February 18, 2007

The end of the experiment (for now)

To bring you up to speed -- in the two previous wood rat blogs I recounted several of my embarrassing experiments on the climbing ability of a local wood rat. Because I had misinterpreted the photos and made incorrect assumptions, I was blissfully pursuing an experimental path of self-deception. Then I realized I had underestimated the rodent's gymnastic skills. To wit, it had been shimmying up a 3/4" pipe and negotiating the overhang of the bait station. So I used a "squirrel baffle" to prevent the trickster from reaching the bait station by the "impossible route". That experiment demonstrated to my own satisfaction that the rodent had shimmied up the 3/4" post rather than climb down the 2" PVC pipe, as I had been mislead to believe. That's where we left off.

I still harbored a belief that the wood rat could "chimney stem" down the inside of the PVC pipe. As mentioned, he had never descended the pipe, either inside or out, to reach the bait station. But I thought he could do it. He might need to build confidence using the tube horizontally before trying to go down it vertically. With the squirrel baffle on the post, the gently inclined PVC pipe was the easiest route to the bait station. (I didn’t think he was desperate enough to try jumping the 28-inch span). I hoped of course to get that one shot of the rat entering or exiting the pipe.

It rained that night, and when I checked the camera the next morning, two pictures showed the rat stepping off the pipe. It seemed to use the PVC as it would a branch.

Another picture however looked like the rat was peering into the tube.

I looked inside the tube. It was still coated with dust. If the rat had passed through, it would have been swabbed clean.

So I fastened the tube to the overhead branch -- the vertical access route. I was leary he might shimmy down the outside of the tube, so I jury-rigged a baffle from a plastic milk container. There was another potential flaw in the set-up. In an attempt to surmount the milk container he might drop to the top of the squirrel baffle below. From there he could climb up to the bait station. To prevent that scenario I suspended the bait station at the end of the tube, and removed the vertical post.

The peanut butter was untouched the next morning. The baffle had worked. I turned off the camera thinking the experiment was over. But when I came to collect the camera the next day the peanut butter was gone! Wonder rat had circumvented the baffle on the second night, and there were no documenting pictures. The inside of the tube was still dusty. If only I had a camera trap that shot video!

I consulted with neighbor Richard, who advised me to replace my shabby plastic baffle with a two-pound coffee can.

The new baffle did the trick. The next morning the peanut butter was untouched. I had enough. The question of chimney-stemming would have to remain unanswered until some later date. I just can’t believe that this wood rat can’t pass through a 2-inch pipe, but for some reason he wouldn’t have any part of it.

Reflecting on all of this I thought about the advantages of a camera trap that uses video.

That night I was sitting at the kitchen counter as my wife was cooking dinner,

"You know, sweetie, if I had a video-camera trap I could get some fantastic footage. It would be pretty neat seeing that rat in action, wouldn’t it?"

"Yeah, that would be nice", she admitted. "But it would be nice to see the leaking roof get fixed too."

Obviously she wasn't buying it. I guess my timing was off.

Friday, February 16, 2007

The incredible rightness of stinking

Three nights before the puma heeded the call of the canned rabbit, a gray fox visited the mossy rock. The initial temptation was probably the distressed voice in the tree, but fox found something on the rock far more alluring -- a brown smudge of goo -- commercial beaver scent. It's made from the beaver's castor glands and their contents. Four weeks earlier I had dabbed the moss with a half-teaspoon of the stuff.

Beavers scent-mark their mud mounds with castoreum. It's strange sweet smell is due to large amounts of phenolic compounds. Like other animal musks, it is also used as a fixative for perfumes. A manufacturer of tincture of castoreum advises men to use it when they want "to regain sexual vitality" or "to face the social context with the wild energy of the trapper". Sounds versatile.

Back to the fox…it arrived at 8:32 PM , and its tryst with the goo lasted five minutes. The camera photographed the episode about every 18 seconds.

When fox wasn't sliding its neck over the scent it sniffed with the rapt concentration dogs devote to stinky things ("Don’t bug me right now. Can't you see I'm busy?").

But something out there in the dark was distracting fox from the intimate ritual.

Fox's parting act was to leave a deposit…a fecal deposit. "I've been here. I 've absorbed the smell. Now I leave my smell." He had been eating manzanita berries (rather dry and mealy at this time of year).

I don’t believe the critical experiment has yet been performed on what advantage members of the dog family gain from anointing themselves with smelly things. One theory is that the foreign scent makes the animal smell interesting to its peers.

Whatever the function, when fox left it probably felt the incredible rightness of stinking.

Tuesday, February 13, 2007

Wet cat on a rainy night

I've had a camera trained on this mossy rock since December 6. Though I've used scent and sound lures to attract game, it’s not a very active place. I was going to pull it today, but I got a surprise when I checked the pictures.

This photo was taken 4 days ago (Feb 9) during the long overdue winter showers. Unfortunately, the wetting agent I used on the camera lens window didn’t prevent water drops, and I guess it's time to get serious about placing a couple of external flashes for better lighting. I mean, this could happen again. If the mossy rock is on the cat's beat, I can expect the next visit in 7 weeks (see "The owl and the pussy cats", December 2006).

What is it looking for? It's looking for the "canned rabbit". That’s a digital player that sounds like a distressed rabbit in a tin can. I hung it on an overhead limb on January 27. It plays for 5 seconds about every half-minute all-night-long.

My wife was with me the last time I checked the canned rabbit's batteries. When I switched it on for the test run she asked, "What in the world are you doing?".

"I gotta test it, don't I."

"Well, you don’t have to test it when I'm here." She insisted that we depart immediately before the place was crawling with mountain lions or bears.

That was February 3rd. Six days later big kitty heard the canned rabbit up in a live oak and posed on the mossy rock.

Sunday, February 11, 2007

Woodrat tricks codger (continued)

Wood rat couldn’t cut the mustard when it came to climbing down a vertical quarter-inch cord. But could he walk across the same cord if it were horizontal? I pulled a quarter-inch cord taut like a tight rope, and repaired the vertical cord that he had almost chewed through. The next morning the vertical cord was dangling and the bait cup was gone. The pictures tell the rest of the story.

He had fed intermittently for a half hour, and cut the bait free in less than a half minute. I revised my thinking. Making the first cut beneath the food wasn’t so dumb after all. If he cut the rope above the bait it could drop into a thicket below, and that would mean a lot more work. Better to cut it free and haul it home in one set of actions.

There was no sign of the cap that held the peanut butter. He must have cached it in his nest for bedtime snacking. I repaired the set up, and the next night was a repeat performance.

Now that wood rat was a habitual visitor, I expected he would go to any length to reach the reward. So I replaced the 1/4" cord with a 1/8th" nylon cord. I figured a really good climber would hang-crawl along the string to reach the feeding station.

Wood rat would have no part of it. On the next two nights he visited the access route as many as 8 times a night, but would stop where the 1/4" line was knotted to the 1/8" line. There he would look longingly in the direction of the bait. It seemed that wood rat wouldn't walk the line if it was less than a quarter-inch thick.

So far, so good. But now I wondered . . . was wood rat capable of "chimney stemming", — that’s what rock climbers do when they brace themselves and "inchworm" between two parallel walls. I wired a 26" length of 2" PVC pipe, the chimney, between an overhead branch and the platform. The only way he could reach peanut-butter-land, I thought, was to go down the tube. I set one camera trap to monitor the tube entrance, and another to monitor the bait station below.

He visited the bait station for two nights, and I assumed that he was chimney stemming.

But a little knowledge can be dangerous. The picture of the hind-foot hooked over the twig showed that he can't rotate his ankles and cling like a squirrel. Therefore, I thought he was testing it in this picture. He couldn't possibly go down the outside of the tube head-first. He had to be going down inside the tube.

A simple test could prove it. I stuffed an old sock--yes it was clean--into the entrance of the tube, predicting that he would either pull it out and proceed down the tube as usual, or have to forego dining at the bait station.

When I looked at the pictures the next morning, I realized the rodent had tricked me.

He didn't remove the sock, but there he was on the platform eating the peanut butter. Damn! My design was flawed. I had allowed him two options--go up the post or come down the tube. Not good experimental design. My early assumption that he couldn't climb the 3/4" aluminum post had been wrong. Now I was wondering if he ever came down the tube at all--inside or outside.

So I removed the tube to see if he could climb the post.

Surprise! The next morning's pictures showed the rat on the platform.

He could have gotten there only by jumping, levitating, or shimmying up the post. There were no climbing action shots, but there was this picture of him on the verge of descending with a mouthful of peanut butter. I had the feeling I was finally getting closer to the truth.

If you think you can bear any more of this, stay tuned for the final episode.

Thursday, February 8, 2007

Wood rat accepts the challenge

Okay class, today we're going to see how the scientific method can be used to explore an important and unanswered question: how well do dusky-footed wood rats climb?

The irrepressible mammalogist Jack Cranford reported that radio-collared wood rats spent 40% of their time above ground foraging in shrubs and trees, and the late E. H. Vestal described a worried wood rat leaping three and a half feet—a rather squirrel-like achievement. So, it's fair to ask: is Neotoma fuscipes a confident and acrobatic climber? Or a cautious climber? It was time to subject wood rat to some climbing trials and put the camera traps to good use.

Where to begin? Go to the literature! Linsdale and Tevis, in their book "The dusky-footed wood rat" reported a rat climbing a poison oak vine. Poison oak vines come in various thicknesses, but cutting them for experiments can have uncomfortable consequences. So my first question was: can wood rat climb a 3/4" manila rope?

I tied the rope to an overhead branch of oak, and moored the other end to a log on the ground. Only by climbing down or shimmying up could woodrat reach the peanut butter feeding station in the middle of the rope. I hoped for a picture of him clinging to the line like a mountaineer.

Wood rat accepted the rope-climbing challenge, and cleaned up the peanut butter the first night. In fact, he made several visits. I assumed that he descended the rope from the overhead branch. It seemed easier than surmounting the feeding platform. Whatever he did, he did it quickly, because there wasn't a single picture of him coming or going.

Time to "raise the bar". The next night I replaced the vertical rope with a 1/4" cotton clothesline. I also replaced the plywood platform with a bait cup strung on the cord.

No longer could he sit and dine.
He would have to feed while on the line.
Ahah! Two nights passed with nary an image.
Was the 1/4" line beyond his limits?

Or was woodrat digesting in the stomach of a fox or bobcat? It was too easy to discover his limitations, and I wondered whether I had somehow exposed him to danger. I mean, like...gee whiz...maybe he attracted a predator while scurrying about trying to reach the peanut butter.

Okay, let's make it easier for the guy. On night 4, I used the 3/4" rope to make a bridge. All he had to do was walk across the rope to the clothesline where the peanut butter was waiting.

And that's exactly what he did. The next morning's photos showed woodrat alive and well, and eating peanut butter like there was no tomorrow. I could only conclude that he was no match for his crazy ninja Malaysian relatives (see the previous blog, mates). Climbing the vertical clothesline (1/4") was beyond his ability. He seemed a little resentful tugging at the cap and chewing the line, but he wasn't clever enough to cut the cord above the bait. The unfinished meal was still there. I felt a little disappointed and smug at the same time. But all that was to change. Wood rat had some tricks up his sleeve. (Stay tuned for the next episode).


Cranford, J.A. 1977. Home range and habitat utilization by Neotoma fuscipes as determined by radiotelemetry. Journal of Mammalogy 58(2):165-172.

Linsdale, J.M. and L.P.Tevis. 1951. The dusky-footed wood rat. University of California Press, Berkeley.

Vestal, E.H. 1938. Biotic relations of the wood rat in the Berkeley Hills. Journal of Mammalogy 19:1-36.

Tuesday, February 6, 2007

Ninja rats of the Bumbun

A studly wood rat with an addiction to peanut butter lives about 50 yards from the house. For the past week I’ve put him through a series of climbing trials. But before I post that blog I want to share a deep secret—my fascination with the climbing ability of rats. It started the night of October 21, 1991 in peninsular Malaysia’s national park—Taman Negara.

We had decided to sleep 30 feet above the jungle in the "Bumbun" ("Boomboom" is close enough)—a wildlife observation blind. The elevated cabin was big enough to sleep 12 people, and rested solidly on massive posts. It looked like a titan gazing over a clearing in the jungle, where the park staff had created a salt lick to attract wildlife.

That morning at park headquarters we bought fried chicken and cheese sandwiches for the overnight outing. As the young lady of the kitchen staff handed us the bags she advised us to hang them from the strings on the Bumbun’s rafters.
"Huh?" I responded.
"Sometimes a rat will eat your lunch", she explained.
"Rat like fried chicken very much. Hang bag on string, they can’t get it. No problem", she giggled, "okay?".

When we climbed into the bumbun that afternoon we didn’t need a shower. A torrential downpour had taken care of that, so we changed into dry clothes, and prepared for a night of wildlife observation. The park had provided engaging reading material—a log for tourists to record their natural history observations.

Most of the entries were tales of red-eyed wayfarers defending their food bags against a determined army of rats. The rodents came in various sizes, but we learned they all had uncanny abilities to invade the bags of food. There was enough material there for a Ph. D. thesis and a Stephen King novel. I knew that peninsular Malaysia boasted of having at least 20 species of rats, and the log’s colorful descriptions assured us we would see at least a few of them up close and personal.

We ate our modest meal, carefully wrapped the remains for tomorrow’s breakfast, and hung our bags from the rafters. Then it was dark. I tape recorded night sounds, and periodically we saw movement at the salt lick, but the beam of our flashlights proved we were imagining things. When my wife and I climbed into our bunks, we promised to wake each other up should the rats make an appearance.

At 2:00 AM, asleep and enfolded in the moist warmth of the tropical night, I felt something on my foot. With one tremendous power-kick I tried to launch the little bugger into outer space.
"Do you know what you just did?" came my wife’s voice in the darkness.
"I got him, didn’t I?"
"No, you almost kicked me in the face. The rats are here, but I couldn’t wake you up."

And there they were in the beam of the flashlight—not the scrofulous imposters described in the log, but nimble fellows, gliding along the rafters with their russet coats, white bellies, and blueberry eyes. There were two species. One had a tail as long as the head and body. The other had a noticeably longer tail. But they were no ordinary rats. These rafter-runners were pumped up like ninjas. The smell of the cheese sandwiches and fried chicken was driving them crazy. Their speedy peregrinations seemed to be a race to see who would be first to triangulate the food by scent.

What we failed to notice was that one of them had already gotten into the food bag, which was vibrating with its frenzied feeding. I climbed down from the bunk and gave the bag a flat-handed smack. Waaaaah! Such reflexes and coordination! The nibbler literally shot up the string like a yo-yo. That's not something many rats can do. These guys were built for climbing.

The ninja rats were rash and reckless, and though we defended our lunch bag, it was impossible to fend off "Yo-yo" and his kin. It was their turf, and we were outnumbered. By 5:00 AM we were tired of the game, and the rats were full of chicken, cheese, and bread. It was time for bed, they had earned their keep, and I knew something I didn't know before--some rats are damn good climbers.

Monday, February 5, 2007

Hunting pumas with kindness

Dr. Rob Horwich of Gays Mills WI just responded to the previous mountain lion blog:

"I recently heard about that lion attack and another where a mother defended her 7-year-old against a cougar for an hour. I think California should institute the old cougar hunts with dogs (but in this case the "hunts" should be non-lethal). I think that would probably give the mountain lions some fear of humans. In Belize the mountain lions are described as "upstart", but they are smaller in Belize, and I am unaware of any attacks there. By the way, I recently heard about a huge pack of 53 squirrels bringing down a cougar, so once again nature establishes a balance."

Horwich’s "benign hunting" idea has merit. Use aversive conditioning to change the puma’s minds from ‘people are prey’ to ‘people are scary’. If the idea conjures images from Stanley Kubrick’s screenplay of Anthony Burgess’s "A Clock Work Orange", allow me to reassure you. We’re suggesting a kinder and gentler aversion therapy than that.

Here’s my take on it. First, consider an area where wildlife biologists deem people to be at high risk of attack by pumas. The hypothetical area has a known population of pumas, a low population of deer, and is frequently used by hikers, mountain bikers, and joggers, who occasionally report sightings of prowling pumas. Maybe harmless puma-human encounters have already taken place. In other words, the clock is ticking.

Responsible wildlife authorities would be scientifically prepared for the undertaking. They would have baseline information on puma-human encounters, and an index of puma abundance based on indirect census methods, such as counts of sign and camera trap records. Next, the wildlife biologists would stage mock hunts. Winter might be the best time. That’s when puma mothers teach their cubs to hunt. The hunters themselves would be professional wildlife biologists, and they would track the lions with hounds until treed. Have you ever seen a picture of a treed puma? Their body language tells it all. If you will excuse my anthropomorphism, they wear a look of terrible humiliation. After a few unpleasant encounters the sight and sound of people and dogs will give pumas what we Californians call "bad vibrations".

If the method works, pumas would avoid rather than stalk people. In any event, the field surveys would give quantitative measures of success or failure. In other words, if the cats avoid the area and puma sightings decline, we could consider the method successful.

Having worked for the government for many years, I know that bureaucrats usually do not cotton to really good hare-brained ideas. So I would anticipate two kinds of responses. The "argument of personal responsibility" would maintain that the hiker who is informed and cautious about pumas is a safer hiker.

Good bureaucrats also use more than one excuse. The coup de grace to the well-intentioned but misguided suggestion is the "argument of fiscal limitation". "Your suggestions, while interesting and of possible utility under specific circumstances, are not feasible for economic reasons." This is usually followed by a litany of statistics about the department’s enormous scope of responsibility, low staffing levels, and equally important competing needs. Your hair-brained idea is dead meat.

So, let "benign puma hunts" increase departmental revenues. It could be tastefully done. There would be no shortage of well-heeled Silicon Valley naturalists who would pay big-time to tree a puma and shoot it (with a camera). Hey, aren’t Apple’s latest operating systems named after the big cats? What are we waiting for? Thar's gold in them thar hills!

Friday, February 2, 2007

When a mountain lion attacks

My heartfelt sympathies to the Hamms, who fought off a mountain lion attack last week. The couple’s chilling description of the ordeal and their determined defense has inspired a great deal of interest and compassion, not to mention lame rhetoric and political commentary. Fortunately, Mr. Hamm is on the mend, after a turn for the worse due to infection. The Hamms have always enjoyed hiking in wild places, and I hope they won’t give it up after this experience. But if they do, so be it. You can’t really blame them.

California’s wildlife advocates invoke changing demography to explain the increased frequency of mountain lion attacks. It stands to reason. The state’s landscape looked a lot different in 1849 when a very sick wagon train captain named J. Goldsborough Bruff (1804 - 1889) decided to call it quits. He dropped out somewhere in Lassen County, wintered in a shanty, and kept a diary. His account gives perspective on what it was like when wildlife outnumbered people. Bruff ran out of food, but the native Yahi offered no succor. Nasty encounters with a steady stream of unsavory fortune seekers had already taught them to keep a low profile. He resorted to scavenging the carcasses of abandoned oxen and big game killed by wolves, grizzly bears, and mountain lions. The predators didn’t leave much meat, but he lavished praise on the choice broth he concocted from the boiled bones. No doubt wild game outnumbered people one hundred and fifty years ago. There was even enough carrion around to support a population of condors. Bruff knew—he shot one.

Long gone are the wolves and ‘grizz’, but the California Department of Fish & Game estimates we share our state now with as many as 6000 mountain lions. And the census takers tell us the golden state has 35 million people. (It’s easier to count people.) The place is changing in other ways. Most of the quaint towns of the coast range, foothills, and Sierra Nevada have given way to burgeoning suburban communities. San Francisco’s bay area baby boomers have migrated to the foothills and beyond into the Sierra Nevada, so a lot of people now live much closer to nature. Mountain lions and other predators must see or encounter a lot more people than in the past.

There’s a clear and present danger when large predators encounter people more often than their normal prey, and this might have been the case with the lion that mauled Mr. Hamm. Cal Fish & Game officials killed a pair of mountain lions near the site of the mauling, and identified the female as Hamm’s attacker. Mountain lions are solitary, which means the female was with her offspring or was having a fling. Either way, two cats get half as much to eat when they make a kill. To eat normally they have to kill more often.

When something like this happens, I get a lot of free advice from family and friends. Normally they view my camera-trapping sorties into the woods as harmless eccentricity. In the wake of near tragedy they behave like officials of the Occupational Health and Safety Administration (OSHA). I can’t defend my outings with the old arguments about probability—"I’m telling you the odds are better of getting hit by lightening than killed by a puma."

But I don’t really want to tempt fate, so I have to consider the expert advice. Don’t go into the woods alone. Carry a big stick. Don’t run when you see a puma. Make your self look big. Etc. Neighbor Richard advises me to take a sidearm, preferably a double action .38 caliber. Professor Wolfgang Schleidt, my grad school mentor in ethology tells me to carry a black umbrella. (Indeed a 19th century German explorer crossed Africa unscathed by flashing open his umbrella at all threatening beasts). And why not don a crash helmet and neck brace? Pumas invariably attack the head and neck.

I am trying to heed the advice of family and friends. My daughter bought me an air horn, and my cautious wife advised me to take the walkie-talkie on my outings—not that anyone could ever find me should I send an SOS.

So a few days ago it was again time to check the trap line.

"Sweetie, how about a hike down in the canyon this afternoon? Two is safer than one, right?"

"You walk too fast. And with my luck the puma would attack me, the slow weak one. Take the walkie-talkie and the air horn Lauren gave you".

I arm myself with a big stick, the walkie-talkie and the air horn. I leave the other walkie talkie in the kitchen. With my knapsack on my back, I head down into the barranca—"valderee, valderah, valderee, valderah ha ha ha ha ha….",

Safely at destination, I drop my knapsack, and pull out the walkie-talkie to report to home base.

"Okay sweetie (puff puff), I’m here at set 21. . . the mossy rock--where I got the puma pictures. . . Do you read me?"

The walkie-talkie goes "Blurp", and there is silence.

"Okay sweetie", I repeat, "I’m here. . . are you there?"

Another blurp, another silence.

Back at the house, I query my beloved whether she heard me calling, and she answers, "No, I was in the computer room.

"Well, what if a puma had attacked me."

"If the puma attacks call when I’m in the kitchen."

My wife is a practical woman.