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.

Monday, December 31, 2007

Carcass visitors

I hauled this road-killed fawn, a female, into the ravine the week before Christmas. It rained the next two days.

A gray fox found it on the third day, and opened the gut. It fed on abdominal muscle and then the haunch.

On day 5, the winter solstice, this buck paused to sniff at 12:45 AM, leaving this one image.

I'll post the other visitors, and the gray fox, during the next few days.

Happy New Year, folks.

Friday, December 28, 2007

On escaping zoo tigers

I would like to weigh in with a few remarks about the recent tragedy at the San Francisco Zoo where on Christmas Eve a Siberian tiger escaped, killing a young man and wounding two others.

So far there are no witnesses to the escape, but Police Chief Heather Fong did not exclude the possibility of intentional or inadvertent human activities and called for a criminal investigation.

Such a notion is reinforced when a television zoo celebrity like Jack Hanna states that the tiger's leap from the moated enclosure would be "virtually impossible". Apparently he was under the impression that the moat was in compliance with AZA standards.

If working with wildlife teaches you anything, it teaches you not to underestimate the abilities of animals.

The depth of the tiger moat at the outer wall is now said to be 12.5 feet, which is less than 16 feet with a two-foot overhang -- the height recommended by the Association of Zoos and Aquariums (AZA). The width of the moat, as shown in a diagram in the SF Chronicle on Dec 27 -- is 15 to 25 feet, but SF Zoo Director Mollinedo reports that it is 33 ft.

This brings me to 2 observations which are common knowledge among zoo biologists.

First, the leaping or escape abilities of tigers or any other species obey the principle of the bell-shaped curve. A barrier may stop most animals--the ones with average abilities, but an exceptionally athletic or clever animal may be able to breach it.

Second, when an animal is strongly motivated to escape, it may perform feats perceived as "virtually impossible". Years or lifetimes may pass before rare circumstances compel a previously complacent animal to attempt escape. Designing an escape proof enclosure must take these realities into account.

Dave Rentz, a childhood habitue of the SF zoo recently posted a good example of the motivational factor at work. In 1959, Carey Baldwin, then the zoo's director tempted the resident tiger with a chunk of meat at the end of a pole. It motivated the cat to take the tremendous leap, which it accomplished on the first attempt. Fortunately, it ricocheted back into the enclosure. That was enough to decide the director to curtail the tiger's access to the outdoor enclosure.

That was nearly 50 years ago, and since then the zoo and the tiger exhibit have changed a lot.

It is possible that Tatiana simply decided to make her break at the time the three young men were outside the enclosure, and then the cat went into predation mode.

It is also possible that one or more of the young men crossed over the public guard rail and taunted the cat, thus giving it motive to breach the barrier and "pursue the prey". I have a feeling that the survivors of the attack may know some things that haven't yet come to light.

Zoo workers must protect the public from the animals and the animals from the public. In reality they are called upon to check the escape tendencies of their charges far less often than they are called to protect people from the consequences of their own ignorance or stupidity.

In any event, the zoo is ultimately held accountable when an animal escapes. More often than not, animal escape policies kick into practice and disaster if not embarrassment is averted. But now and then an animal escape takes a tragic turn, as did this one, and the zoo director's worse nightmare comes true. It remains to be seen whether the AZA accreditation team that routinely reviews the practices and conditions of member zoos, actually failed to note this deficiency and/or enforce its recommendation.

All of this reminds me of a similar tragedy that Dr Theodore Reed, former Director of the National Zoo in Washington DC related to me before his retirement. Nearly 50 years ago, a small child in the care of an inattentive grandparent squeezed through the public barrier and walked up to the lion cage. The cat reached through the bars and killed the child instantly. It took this tragedy for the US Congress to finally respond to the zoo's standing request to fund major renovation and safety upgrades.

Wednesday, December 26, 2007

The call of smelly crab

Not back to the normal codgerly routine yet, but thought this frame was worth posting. Though I got 43 pictures in two nights, none captured foxiness as well as I would have liked.

What the picture shows is that gray fox is powerfully attracted to smelly old crab shells. It came to the lure the first night. If I had baited the site with only a mouse or a chicken neck, I probably would have waited several days for the fox to show.

By the way, here you can see the volcanc capstone that is so prevalent in this area. The gray fox is quite at home here, and next to striped skunks is my most frequent camera trap visitor.

Saturday, December 22, 2007

Me, the old fool

There's no fool like an old fool. That's me.

As far as protecting my cameras from bears, I did well this year. That is, until December when I let my guard down.

I thought the bears were sleeping by mid-November. I had consulted the literature and that's the schedule in Washington State. Here in northern California I assumed it would be a little later.

I hadn't seen any bear scat in the woods for a few weeks, and since we've had some freezing weather, I left the bear guards at home. I put 6 cameras out this month, and the camera set you see above seemed to hold most promise. At least the setting was more picturesque.

On December 17th or 20th a bear smelled the gopher I had hung behind the leaning fir next to the log. The camera must have flashed, and the bear went for the camera. This is when the spikes on the bear guard give the bear an attitude adjustment. But there was no bear guard.

The bear opened the case, pulled the camera out and at the same time tore out the internal wiring to the controller. The case was held to the tree with a double loop of bungie cord, so the lid snapped shut and protected the batteries and controller from the weather.

The bear carried the camera to the log and left it face down on the moss. There's a tooth mark in the LCD.

Then the rain came.

The only good thing about a bear-trashed camera is looking at the pictures and witnessing the crime being committed. But not one of the 40 pictures turned out. They were all black images.

I am still drying the camera near the woodburning stove, and spent yesterday morning putting bear guards on the other cameras.

This would never happen to the redhead. She doesn't take chances.

I'm afraid I fit the definition of an "old fool" to a T.

Friday, December 21, 2007

Solstice patch visitors

I couldn't take Terrierman's winter's solstice advice today, because I don't have a dog.

Yet something magical happened. Dogs joined me in my morning camera trap beat. I didn't know I had company until I switched on the camera and viewed the images. I don't know whose dogs they are; I've never seen them before.

But there they were, a few minutes ahead of me on the trail, pissing on my scent patch.

Thursday, December 20, 2007

Stalwart pariah dogs -- Part 1

"It is on record that in the station of Gumsoor not a single dog escaped, and nearly every resident of India who has ever camped out in the jungle where leopards are, or has lived in 'the hills' has had some tragic experience of this mania of the leopard for dogs." Belgravia, 1883

Back in my Nepal days, there was a small patch of scrub jungle in the dusty town of Narayanghat. It was on the west side of town not far from the Tikoli Reserve Forest. Like a lot of Nepal's terai it looked rough and scraggly. In fact, it mirrored much of what had happened to that exotic belt of jungle when foreign aid and DDT opened the area in the 1950s. With the threat of malaria gone, the local Tharu people, who were resistent to the disease found they had new neighbors from the hills, and the land started to change. Men and boys had long since lopped and cut down the trees, women had gathered the sticks for firewood, and goats and cattle had stripped the forbs and grass. The remaining thicket was a thorny wasteland.

In the early 1980s the local jemandar or headman decided to make use of the land and hired villagers to slash the thicket. In the center of the thicket they found an opening littered with bones. The Smithsonian Nepal Tiger Ecology Project was going full tilt at the time, and word of the find reached the American and Nepali graduate students working on the project.

The bones were of pariah or pie dogs, and there were many. The villagers had found a leopard's lair beside a dusty road in a busy little town. The number of bones was testimony to the leopard's many successful forays into the village, and the thicket had been the perfect hideout.

It seems no one had seen or heard the cat, and if anyone heard the cries of dying dogs it probably didn't register, because dog noise is the night song of the Nepalese village. Rarely does anyone notice a missing pie dog -- they are more or less communal property. Dogs come and go, and in Narayanghat they were a sustainable resource. If the smell of carrion drifted from those scraps of dog meat in the leopard's lair, they blended well with the town's organic ambience.

The leopard's fondness for dogs is well known in rural Asia, and baiting leopards with a village pie dog was an acceptable practice of colonial sportsmen like J.A. Duke, who nearly 80 years ago was moved to pen his experience with one. Indian civilian's like Duke, a policeman and a hunter, were frequently sought to shoot maneaters, rogues, crop raiders, and other forms of nuisance wildlife.

In this case, the villagers had appealed for relief from a leopard that had been killing livestock.

It worked like this. If the hunter couldn't find and stake out a fresh kill, he had his shikaries peg a live bait animal to a short tether in a small opening in the jungle. Then he hid in a machan or tree stand within close shooting range.

Success depended on procuring a suitable bait animal. Suitability meant that the creature would make enough noise to lure the quarry within shooting range, that it was readily available, and that it could be had for free or at minimal expense.

Duke didn't have the heart to use a tail-wagging half-grown pup. So next he tried a goat. It assumed a "statuesque attitude beside the peg to which it was tied and remained absolutely silent". So much for that one. Another goat attempted suicide by hanging on the rope and "never opened its mouth". Then a pie dog was found, but it's muteness also earned it dismissal.

In Duke's words, "...I was getting a bit fed up and pessimistic. . . .However, I said another dog must be produced."

Finally the shikaris found a stalwart pie dog that showed promise, but it revealed its suitability only after they whacked it a few times with a cane. "The dog was naturally furious and expressed his feelings in fierce growls, and, thank goodness, two or three loud barks." The dog was tethered to the peg and Duke took up his shooting position.

"Not long afterwards the silence was rent by a series of howls, growls, and barks from the dog...," which Duke saw dancing about on its chain facing off the invisible foe lurking in the shadows. With the next uproar the leopard revealed itself in the torchlight. It was circling and swatting at the defiant dog, "but it was obviously deterred from going right in and killing with his teeth by the dog's galant and terrific defence".

Duke shot the leopard, which dashed off and died, while the dog watched its disappearance into the brush with vociferous bravado. As he climbed down from the tree, the dog "...managed to detach the chain and bolted off into the jungle, naturally in the opposite direction to that of the leopard."

Duke noted, "I am glad to record he rolled up in his village alright and complete with chain. He had lost a good deal of skin from his face and chest, but so far as I know is alive and well to this day."



Duke, J.A. 1929. A stalwart pariah dog. Journal of the Bombay Natural History Society, XXXIII(2):428-430.

Monday, December 17, 2007

Pygmy Owl interlude

The other day "Atowhee" at Towheeblog had a pygmy owl interlude in Medford, Oregon, and added the species to his life list.

He writes, "My Christmas Count team was led by Dick Ashford but he and I were both new to this particular territory. His supremely good pygmy owl imitation netted us our only owl for the day: a mid-afternoon Western Pygmy Owl who ignored hundreds of scolding Robins to find the other calling owl. He came within a dozen feet of us. And stared us down as we slinked out of his territory." (Be sure to check out Atowhee's excellent Oregon and California birding blog.)

I've never heard a pygmy owl, but had a brief acquaintance with one back in the late 1950s. That was in the Santa Cruz Mountains in the days before computer games, cell phones, and "lame boy toys", when kids used to play in the woods.

For some unknown reason, my friend Marvin and I had decided to scale a sandstone cliff above the swimming hole in the San Lorenzo River. It wasn't particularly dangerous if you stayed on a narrow ledge. Half way across we wanted to celebrate our accomplishment and sat down on the ledge hoping some neighborhood kids would show up and see us there. It didn't happen.

I was getting bored and for some unknown reason felt compelled to throw a rock at a broken snag below. When the rock hit the trunk a small owl shot out and swooped up into a small Douglas fir at the edge of the cliff about 40 yards away.

We decided to get a closer look and made our way across the cliff to the Douglas fir. The owl was perched low and near the trunk. It seemed tame, and I decided to climb up on the opposite side of the trunk. It flew up a couple branches, but it didn't fly away.

At this point I asked Marvin to go home and get a length of green fishing line, a coat hanger, and a large paper grocery bag. He was back in a half hour, and we made a noose. The green fishing line had proven itself excellent lizard noosing material. I had to abandon my idea to use the straightened coat hanger as an extension to the noosing stick, because it was too hard to bend it around the stick.

I tied the noose to the stick, climbed a few yards up into the tree on the opposite side of the owl, and slowly raised the stick up to the birdl. It flew up a couple branches to a higher perch. On the next try I was able to lower the noose over its head, but the noose was too small. The owl shook it off and again flew to a higher branch.

I lowered the stick and opened the noose, then climbed higher, peeked around the trunk and tried again. Once more the same thing happened.

I realized the slip knot was too big, and no matter how slowly I had raised the stick the noose became smaller. This time I tightened the slip knot slightly and opened the noose as wide as possible. I knew it was my last chance and climbed very slowly. We were now almost halfway up the tree, maybe 40 feet up.

I raised the stick and watched the noose get smaller, but this time it seemed ample. The owl was as calm as before, but as I lowered it over its head it suddenly took off.

For a split second I thought it was gone, but then I saw it dangling from the noose. It had flown through the loop and was caught by one foot. I reeled in the catch. Back on the ground, we loosened the knot and dropped the owl in the paper bag.

Triumphant, we crossed the river and headed home. That Sunday my family drove back to San Francisco.

The pygmy owl was quite tame, sat on a perch in my room, and took meat from my fingers.

When I got home from school the following Tuesday, the window to my room was open and the owl was gone. My parents were tolerant of pets, but someone opened the window and the owl "flew the coop".

Years later I found out why. For some unknown reason, my grandfather didn't approve of captive owls.

Sunday, December 16, 2007

The cat's ear

The camera trapper's occasional rewards are usually a meager number of decent pictures, and by that I mean well-framed images of the animal in a visually pleasing setting. The best wildlife pictures are taken by people who control the shutter themselves. Camera trappers want dazzling pictures too, but by playing out a kind of frontier fantasy they choose to do it the hard way. Because the odds are against them, they're often happy with less. Like this bobcat's ear.

Until this picture, only 3 carnivores had passed the cameras at Point Reyes National Seashore. That's a small percentage of almost 2000 photos taken during 215 camera trap nights (# of cameras x number of nights).

The best carnivore photo -- of a long-tailed weasel was a thrilling surprise. A raccoon's rear end, and a partial view of a striped skunk weren't worth keeping.

Any picture of a bobcat though is a welcome event, even if it's just an ear. This cat stood still long enough for the camera to take 4 pictures of ears and whiskers.

The camera set on this trail was the most productive of the ten sites. I didn't get any mountain beaver photos here, but there were numerous pictures of brush rabbits and a large woodrat, not to mention a few pictures of shrews and a red salamander.

The image speaks to me. "If you want a better picture, dummy, move the camera back."

That would be hard to do because the trails are narrow in that tangled thicket. If I try for bobcats at Pt. Reyes in 2008, I'll find some trails that are in the open.

Friday, December 14, 2007

California's possum diaspora

The Virginia opossum was one of my last camera trap visitors at Point Reyes National Seashore. As reported in my last possum post, this curious possum was also attracted to the electronic flash and gazed inscrutably at modern technology.

The Virginia opossum is one of California's recent mammalian immigrants, but the history of its colonization raises many questions.

What we know is that California's ancestral possums came from MacDonald County, Missouri and Jackson County, Tennessee, and probably other places as well, though no one knows for sure.

Those pioneer possums were tough. It would have been a grueling cage-rattling trip on the transcontinental railroad, but they could have toughed it out during the warm months. Sea travel would have taken more time, and seems less likely, but their sprawling "sea-legs" would have served them well.

At the turn of the last century the Golden State had much to offer its citizens in the way of wildlife, including grizzly bears, but her settlers from the South missed their possums. Possums may not be challenging quarry for the hunter, but memories of baked possum and sweet taters summoned mouthwatering cravings.

Early Californians kept penned possums for food, but they didn't keep them for long. I suspect the possum farmers soon grew tired of their chores, and decided it would be a lot easier to harvest wild possums. Maybe that's why one W.D. Watkins set five Missouri animals free about 3 miles south of San Jose. That was back in 1900. We don't know if they survived, but if they did, rest assured they went forth and procreated. In 1910 several more possums are said to have escaped from a San Jose jeweler and possum fancier. His seven possums came from Tennesee. Apparently possum owners in Los Angeles also had a hard time keeping their stock penned.

By 1913 one hundred opossums had been captured in the greater San Jose area (Santa Clara County), and by 1915 they had apparently made their way over the coast range into the San Lorenzo Valley in Santa Cruz county. This route would have led venturesome possums to the coast, and to easy routes north and south.

An attempt to introduce possums to mountainous Shasta county failed around 1932, but possums from San Jose spread into the San Joaquin Valley, circumnavigated San Francisco Bay, and thence colonized the northern coast range, the Sacramento Valley, and the northern foothills of the Sierra Nevada.

You are looking at a descendent of those hardy pioneer possums. The foggy windswept coastal scrub of Point Reyes is a far cry from the bottomlands of the south, but like the rest of us here, Br'er possum is quite at home.


Gardner, A.L. and M.E. Sunquist. 2003. Opossum, Didelphis virginiana. Pp 3-29 in Wild mammals of North America (G.A. Feldhamer, B.C. Thompson, and J.A. Chapman, eds.). The Johns Hopkins University Press, Baltimore.

Grinnell, J., J. Dixon, and J. Linsdale. 1937. Fur-bearing Mammals of California. University of California Press, Berkeley.

Ingles, L.G. 1954. mammals of California and its coastal waters. Stanford University Press, Stanford, California.

Lidicker, W.Z., Jr. 1991. Introduced mammals in California. Pp 263-271 in Biogeography of Mediterranean Invasions. (R.F. Groves and F. di Castri, eds.) Cambridge University Press, Cambridge, UK


Wednesday, December 12, 2007

Last songs of summer

[female Convex shield-backed katydid, Magalia, California]

The wee minstrels of summer are checking out. The tree crickets have been gone for several weeks now, and I haven't heard any field crickets lately, though I suspect a few are clinging to life under woodpiles and in basements.

The convex shield-backed katydid (Neduba convexa) lasts into December. In the summer, their quiet wheezing song rides the night balm of the foothills. Now the nights are too cold for singing, and only a few stragglers remain.

I heard one male singing feebly on December 9th in the low rays of the afternoon sun. I believe his calls were unheard, and expect this last generation of Neduba will be gone by winter's solstice.

I kept several Nedubas in my office last year to see how long they could live if given warmth, food and water. One female died on December 29th, nearly 5 months after she was caught, and a male caught in November lasted until January 26th.

They continue to sing and court almost to the end, but become lethargic and absent-minded a few days before dying, often in their food dish of ground oatmeal. In the woods it's much the same. They sit in a comatose state until the warmth of mid afternoon arrives. Then they sing and wait. This goes on until it gets too cold. Finally they freeze or run out of gas.

I am tempted to say that in the end these lone minstrels would choose sex over food, but ever since I saw them dead in their food dishes, I just don't know.

Monday, December 10, 2007

Wolfgang's trestle table

When I grew up doing-it-yourself was a virtue. A lot of Americans seemed to think that way -- a lot more than nowadays.

My problem has always been chosing the wrong projects and not finishing them. The wrong do-it-yourself project is building a dulcimer or a spinning wheel instead of fixing a toilet that won't stop. Bending wood with pipe clamps on the living room floor never went over well with the redhead, and neither did unfinished Xmas presents stored in the basement years after the giving.

There were just too many fun distractions, but I am happy to report that those days are now history. I did eventually finish the chest of drawers and other Xmas gifts that awaited completion.

At this time of year, when winter storms flush the coastal creeks and heap logs, drift wood, and redwood burls on the Pacific beaches, I think about beach combing, finding wood with character, and building a sturdy trestle table.

Wolfgang Schleidt had just such a table at his farm house. Zoology grad students gathered around it for evening seminars. Over coffee and Gugelhupf we discussed issues in animal behavior, and there we met Nobel prize laureate Konrad Lorenz in person.

Wolf returned to Vienna, Austria in 1985 and now, retired, lives in an old farmhouse in the countryside.

I wrote him last week:

"I always loved your old trestle coffee table in Maryland. Must look for some drift wood one of these days to make a trestle dining room table. The redhead is not keen on the idea, but I think I can change her mind. The waves on the coast are huge, and a lot of good stuff is going to wash up."

Wolf responded:

"Just for the record: that old trestle coffee table was not made from drift wood, but from the floor support of our old corn house: very well seasoned maple beams, and one piece of oak, that never had seen an iron nail. Therefore, I was able to persuade our lumber mill to run them through their planer, and get them all to the same thickness.

The trick part was to glue them together, without any clamps!

It was in the Fall of 1965, shortly after we had moved into Beall Farm, and all I had were the basic hand tools (Craftsman handsaw, chisels, wrench set, etc. which I still use these days) and a Black & Decker electric drill. So, I got myself an eight inches long ½” wood drill and VERY carefully drilled into each beam two horizontal holes. They had to be VERY carefully lined up for two ½” threaded rods with a washer and a nut on either end, which were used as “permanent” internal clamps. Because I did not want the nuts to stick out, I chiseled out a space around the four holes on the outer beams where the nuts were to be placed, deep enough to cover the hole and nut with a wooden peg.

The only furniture we had at that time were a few old chairs and folding picnic table, left behind by the Bealls,
and our bed and four oak stools we had brought up from North Carolina. I used these four stools for support during assembly in our living room: I set them up, two and two each, with an old board across, placed my beams on top, carefully lined up, applied about a pint of Elmer’s glue to the sides to be fused (as thin and even as I was able to do), pushed the threaded rods through and tightened the nut as tight as possible.

Next morning, when I inspected the fruits of my labor, I found underneath the table top four beautiful lines of pearls on our plush wall to wall carpeting. It was Elmer’s Glue fused to the pile."

Wolf and I seem to have a lot in common.

Friday, December 7, 2007

High tailing hypotheses

Here we are again at Point Reyes National Seashore looking at a brush rabbit high tailing it down the bunny trail. Yes, I am milking the camera trap results for all they are worth.

I always thought that the words "high tailing" originally came from the tobacco stained lips of a gun bearing American somewhere east of the Mississippi. There has never been any question in my mind that the white-tailed deer was the inspiration for this woodsy Americanism.

Apparently not everyone agrees. A competing theory attributes the term to cowboy talk, and the fact that horses also gallop with their tails up. It doesn't matter. A lot of mammals beat a hasty retreat with high tails.

What I want to dwell on here is the eye-catching flight of mammals that leap and bound while ostentatiously flashing white tails and rumps. The high-tailed pogostick gait is called pronking, which comes from the Africaans verb pronken -- to show off, strut or prance. Spronking and stotting mean the same thing, though their origins are vague.

This business of leaping and flashing the fanny became a controversy some years ago when a free-thinking graduate student named Nick Smythe proposed that it evolved in many mammals as "pursuit invitation signals". The conventional wisdom held that tail flagging and the like were alarm signals that aided visibility and cohesion among the fleeing groups. Smythe couldn't reconcile that idea with another observation. When animals like antilopes pronk, they broadcast their whereabouts to predators.

It's probably fair to say that the pursuit invitation idea came to Smythe while in the desert on a horse with no name. (We were office chums so he won't mind me saying that).

He was in Argentina, a student of caviomorph rodents, watching Patagonian cavies, which have been described as rodents trying to be antelopes. When he approached the fleet footed rodents at an oblique angle they would flee and stott at a critical distance of 30-40 meters. Then they would sit and watch him. "If I rode my horse directly at the animals they would gallop straight away. If I rode in such a way as to be in clear sight, but to remain well outside the flight distance. . . .they would freeze and let me pass."

Smythe reasoned that cursorial species like jackrabbits, antelopes, and Patagonian cavies play a game of catch-me-if-you-can with their predators. The predator often decides to give chase, lured by flagging white tails and rumps. His key assumption is that "a healthy prey animal once aware of the predator, stands a good chance of escaping if the predator initiates its attack from outside the flight distance." Unsuccessful chases waste time and energy, but by provoking the chase the quarry brings the threat of predation to closure, and enjoys a net saving of time and energy needed for foraging and other activities.

The publication of the idea apparently caused a stir, but it took 7 years before the other views started to circulate.

The first to object were David Hirth and Dale McCullough, then at the University of Michigan. Years of watching white-tails had given them a different impression, so they examined their data on tail-flagging and another alarm behavior called snorting. For much of the year, white-tails live in closely related female groups or relatively unrelated male groups. Male and female groups tailflagged more or less equally, but female groups snorted significantly more than male groups. Tailflagging, they concluded, is a normal response to predators when the threat is low, "and should be considered a low-cost form of altruism." Female groups snort significantly more often than male groups, which means it probably benefits relatives and is maintained by kin selection.

They felt that the presumption of predator gullibility was a major flaw. Are there no "prudent predators"? If there are no gains to be won by chasing tail-flaggers, wouldn't a crafty canid learn to pursue only non-flaggers? And if so, isn't that an example of a pursuit deterrent signal? And what about plains-dwelling ungulates whose rump patches are permanently switched 'on'? Are these species inviting pursuit all the time? Or do such patches have a different (species recognition) function?

Smythe wrote a rebuttal, but the debate wasn't over.

Bruce Coblentz's critique was titled, "On the improbability of pursuit invitation signals". Coblentz drew on new predator-prey findings from Africa to show that stotting Thomson gazelles gain no advantage when pursued by hunting dogs and spotted hyenas. As for Smythe's assumption about the prey's net energy savings, Coblentz pointed to new findings on the critical energy balance of white-tailed deer in winter, when the costs of strenuous exercise alone can be fatal. Under those conditions, eliciting a predator chase would mean death even if you escaped. It was pretty convincing evidence, but he conceded that the rival group cohesion hypothesis also needed better substantiation.

Next, ornithologist Keith Bildstein jumped into the fray. Like Hirth and McCullough, he also impersonated a predator, this time with white-tails in Virginia. He also used golf balls to mark the distance covered by fleeing deer. Bildstein drew attention to the fact that tail flagging is indeed directed to the predator, and that deer are more likely to flag when at greater distances (75m) from the predator. He did not concur that tail flagging was exclusively a cohesion signal, but didn't agree that it was an invitation to pursue. His take was that it most likely serves as a pursuit deterrent or predator detection signal.

At about this time came Tony Pitcher's antiambush hypothesis -- "that stotting evolved as a secondary defense to reduce the effectiveness of ambush attack by socially hunting predators". That's right, high-jumping helps the antelope see who's lurking in the bushes. Somehow the debate had missed this point.

Then a bird study from down under clarified the pursuit invitation issue further. Australia's eastern swamphen flashes its white tail feathers to potential predators just like tail-flagging mammals, but they don't do it while running or flying away. The tail flashing signal is covert to other swamphens, and overt to predators, and its frequency increases as ground predators (like people) get closer. It flashes whether alone or in groups. When cover is available, it just hides. When a predator appears within its flight distance, it flees without signaling. D. J. Woodland and coworkers concurred with Smythe that such signals are intended for potential predators, but argued that they dissuade rather than goad the predator to attack -- for swamphens, the pursuit deterrent hypothesis made the most sense.

Finally someone did an experiment, and while the example is peripheral to pursuit invitation, it still bears on the issue in the meandering way that science solves problems. Roger Powell examined the role of black tipped tails in weasels to predation by raptors. White winter coats make weasels hard to see in snow, but black-tipped tails would seem to give them away to predators, just as white tails and rump patches do in ungulates. Powell trained three red-tailed hawks to attack six models of weasels (2 sizes) scooting over a flat simulated snowfield. The models differed in the presence and location of the black spot. Guess what? Attacking hawks had trouble striking the pure white models, but clearly zeroed in on the black spots. They easily struck models with a black spot on the body, but missed models with the black tail tip. Powell didn't conclude that the tail markings of weasels evolved to invite attack, but thought they served to deflect the strike away from vital parts. Thus we have the predator deflection hypothesis.

Testing hypotheses is like trying on new shoes. You take the shoe that fits. The pursuit invitation hypothesis was rejected by some, while others cobbled its parts into new hypotheses that fit their data. Most hypotheses have short lives, but if they make it to print, they are likely to stimulate further investigation and get chewed up along the way.

That's how we learn new things, and find out that we've only scratched the surface.


Coblentz, B. 1980. On the improbability of pursuit invitation signals. American Naturalist, 115:438-442,

Hirth, D.H., and D.R. McCullough. 1977. Evolution of alarm signals in ungulates with special reference to white-tailed feer. American Naturalist, 111:31-42

Pitcher, T. 1979. He who hesitates, lives. Is stotting antiambush behavior? American Naturalist, 113:453-456.

Powell, R. 1982. Evolution of black-tipped tails in weasels: predator confusion. American Naturalist, 119:126-131.

Smythe, N. 1970. On the existence of "pursuit invitation" signals in mammals. American Naturalist, 104:491-494.

Smythe, N. 1977. The function of mammalian alarm advertising: social signals or pursuit invitation. American Naturalist, 111:191-194.

Woodland, D.J., Z. Jaafar, and M.-L. Knight. 1980. The pursuit deterrent function of alarm signals. American Naturalist, 119:748-753.

Wednesday, December 5, 2007

Toyon stake out

The botanical explorer Frank Kingdon Ward would have called it "berried treasure". Toyon or Christmas berry (Heteromeles arbutifolia) is one of the chaparral's most colorful shrubs, and an irresistable attraction to birds. Last winter the birds had gobbled up most of the toyon berries by the end of January.

This year I decided to stake out a bush with a camera trap, and so far the only visitors have been American robins. The birds were leary of the camera, and spent a lot of time staring at it, but eventually relaxed enough for a few pictures of berry gobbling. This was a trial, and the pics leave a lot to be desired, but one thing I learned is not to stake the camera too close. The weight of the bird can pull the berry cluster down and out of sight.

Toyon fruit is apparently edible by people. California's settlers used to eat the mealy little berries fresh and dried, and also made them into custards and wine.

I learned a long time ago that while bird berries may be edible they don't always make for a pleasant dining experience. The realization came about when I talked the redhead into making a mulberry pie. I believe that Euell Gibbons had talked it up in his book Stalking the wild asparagus. There was a huge mulberry next to the house, and I handpicked the choicest fruit. The redhead labored to pull out the stems against my advice, and added sugar, and then lemon to zest up the flavor.

The smell of that baked pie just didn't temp us like blackberry pie, and nothing short of starvation could have made me take a second piece.

The chickens enjoyed it immensely.

Monday, December 3, 2007

Patch Update # 2

Checked the patch today, and found that a puma made an appearance at 9:54 in the morning 2 days after Thanksgiving. That was 4 days after I changed the batteries and memory stick. This was the only picture.

I didn't refresh the scent patch, and evidently it didn't hold much interest. What a difference from back in July, April, and May. If she had paused to sniff it I should gotten one full body shot.

She looks a little thin, and maybe that explains why she's on the prowl at this time of day. So, camera trapping season on pumas has officially opened.

Oh, yes, a few turkeys walked by too.

Sunday, December 2, 2007

Red Sally, the cold blooded night stalker

October 25, 7:27PM: We are back at Point Reyes National Seashore again, where a cold blooded night stalker padded past the camera looking for edible victims in the leaf litter.

This record of an Eschscholtz salamander (Ensatina eschscholtzii) was a stroke of good fortune. The camera's passive infrared (PIR) sensor does NOT respond to cold moving bodies. A warm moving body -- brush rabbit, deer mouse, or wood rat -- must have triggered the camera just before the salamander moved out of the frame. Whoever it was, I am grateful.

Ensatina, a salamander without lungs . . . I remember it well from collecting forays on the San Francisco peninsula. Its fruity (ripe persimmon) complexion, laterally compressed tail, and constricted tailbase give it away as the yellow-eyed subspecies xantoptica -- commonly called the red salamander.

Red Sally's fiery coloration reminds some predators of bad dining experiences. It is believed to trick birds by looking like a newt. It is a mimic of newts. We have three species of newts here, and all of them have skin laced with tetradotoxin, the same stuff that makes pufferfish deadly poisonous. Birds that have gagged on toxic newts are tricked by Red Sally the imitator. But the salamander probably doesn't fool snakes, that have limited color vision, but a powerful Jacobson's organ.

Red Sally chooses a subterranean existence until the fall rains. Ninety-four years ago and not far from here the California naturalist C.L. Camp found a red salamander nest 2 feet deep in a mountain beaver burrow. Why not? Coastal scrub offers little in the way of ground cover and fallen logs, but mountain beaver burrows and woodrat nests offer a stable microclimate and plenty of insects, though they don't guarantee freedom from predators.

Stebbins notes that "When the surface is damp and temperatures not too high, considerable time is spent above ground where most feeding probably occurs." That's probably what Red Sally was doing here.


Stebbins, R.C. 1951. Amphibians of Western North America. Berkeley and Los Angeles.