The Goose Pen

A goose pen with a circumference of 38 feet
can hold a lot of geese or sleep several loggers.

If you have seen one redwood you have NOT seen them all.

This old veteran was hidden in the brush and almost escaped our notice.

Standing 20 feet high, with a dbh (diameter at breast height) of 12 feet, it was one impressive stump and deserved thorough exploration.

I climbed down through a rent into the cavity 4 feet below the ground.

Several passages of differing size led to the outside through the charred walls, and internal recesses reached deeply into the roots.

This was one helluva place for a camera trap; so we climbed through the slash back to the truck and returned with the gear.

Then it started to rain.

The stump was not much of an umbrella; the camera case was soon wet, and the camera lens fogged immediately.

I tried drying it, but it was too dark to see what I was doing. I gave up and hoped for the best.

Before continuing our rounds, we interred some pieces of road killed squirrel into and under the old stump's walls.

Later that afternoon I told Lowell about the magnificent stump.

"You know what they call them up here?", he asked.

"Goose pens. The old timers used to pen up their geese in those stumps." 

The goose pen rewarded us with 107 photos of 9 species, and a success rate of 95%, which means there were few false triggers.

The deer mouse and wood rat of course were the first to show, but a hermit thrush appeared shortly after the alders dropped their leaves into the stump.

A Trowbridge shrew almost escaped my notice, but there it was, the voracious and fearsome midget mammal.

The brush rabbit's venture is a mystery. What was the attraction? It seemed a risky place considering the other visitors.

Of all the visitors, however, Fang the opossum spent the most time there (7 visits, 37 photos).

A bobcat paid three visits and left 11 images,

while a curious gray fox and a wet bear paused to examine the camera.

Though I like other images better, the shrew and the bear gave me the biggest thrill.

When I got home I realized I was missing my side cutting pliers.

You can see their blue handles under the bobcat's foot.

The blue plastic grips were all but missing when I recovered them.

There were rat nibble marks on the remaining traces of plastic, but the pliers still work.

Skinny cat nails plump bunny

The young bobcat caught the brush rabbit on the evening of June 11.

I couldn't see the rabbit when I scoped the pictures on the camera's LCD the other day, but there was no mistaking it as a rare event when I saw it on the computer screen this evening.

I think the dead rabbit is the same one the cameras photographed between May 31 and the morning of June 9. (I have three cameras on this trail.)

No bunny however was photographed after June 11 and until I checked the cameras on June 30.

The rabbit had the habit of loafing on the trail. I got multiple images of it.



This trail seems to be on the cat's regular beat.



Between June 10 and June 23 the cameras photographed the same cat on 5 occasions.

Look at the it's right foreleg and you will recognize a distinctive broken band of dark fur.



It's the same in all photos, except the one with the dangling rabbit.



My guess is that the hunter is the same skinny bobcat seen in the other pictures -- a young adult probably from last year's litter.

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.


References

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.

Briar Jennies and dumb bunnies

Though I set three camera traps for mountain beavers, there was no escaping the brush rabbits. "Briar Jennies" thrive in the coastal scrub.

Kids may believe rabbits lay eggs, but grown-ups deem rabbits to be commonplace, uncharismatic, and often a nuisance.

I've always wanted to believe that knowledge begets appreciation, so my goal today is to convince you that these benign-looking creatures are an evolutionary success.

Let's start with the generalized rabbit body plan (we're talking rabbits and hares here). It's an enduring 50 million-year-old design that first appeared in the middle Eocene when the Lagomorpha split from rodents.

Rabbits and hares (of the family Leporidae) are built for speed. Elongated limbs and feet endow them with a long stride, while their speed comes from the concentration of muscles in the upper legs. They represent two basic models: hares are lanky high-speed runners that out-distance and out-manuever their pursuers. Rabbits are compact sprinters that rely more on cover to elude their predators. Generally speaking, these differences reflect their use of more open versus more closed habitats.



They have a remarkable digestive system that begins with the split upper lip. The "hare-lip" works like two fingers with the jaws, incisors and tongue to select plant parts with magical effect. The single pair of lower incisors cuts vegetation against two pairs of upper incisors, one in front of the other. An effective apparatus for pruning plants.

The two-cycle digestive engine is also uniquely lagomorph. During their wakeful nocturnal phase rabbits frequently churn out numerous bunny beans, which are recycled products of digestion. During the restful daytime hours they eat partially-digested soft feces from the caecum, which is essentially a large appendix or "fermentation vat" attached to the intestine. It sounds yucky, but it works quite well when you have to extract energy from a diet heavy on fiber. The first passage through the gut doesn't quite do the job. That's why rabbits and hares spend their inactive hours dozing, grooming, and eating partially digested feces (refecation).



When it comes to reproduction, evolution has tinkered less with rabbits than hares. The nestbuilding habits of rabbits, and the often naked, blind and helpless condition of their young are more primitive characteristics shared with most rodents. Hares on the other hand, use a dirt depression as a birth site, and the furry and wide-eyed young are hopping about in a few days.

But neither rabbits nor hares are stay-at-home moms. They stoke their young with highly nutritious milk only once a day. With an average litter size of 3 young, and as many as five litters during the 7-month breeding season, the brush rabbit can produce 15 young a year, and an ample food source for predators.

Predators hit the "dumb bunnies" hardest. The complacent and dreamy-looking weanlings are sitting ducks for bobcats, foxes, coyotes, and weasels. Only the quick-witted survive to reproduce.

The brush rabbit seen here looks to be a young of the year. Indeed it was visited by a larger rabbit, possibly its mother.




It spent most of the day lingering in front of this mountain beaver burrow, which it used no doubt for escape. When the weasel visited, it "made itself scarce". Thus, this rabbit seems to have advanced beyond dumb bunnyhood.

If all goes well, it will become a Briar Jenny, and in a few more months will go forth and procreate.

And if it doesn't go well? Then another rabbit will be there to take its place.


References

Asher, R. J., J. Meng, J. R. Wible, M. C. McKenna, G. W. Rougier, D. Dashzeveg, and M. J. Novacek. 2005. Stem Lagomorpha and the antiquity of Glires. Science 307(5712):1091-1094.

Chapman, J.A. 1974. Sylvilagus bachmani. Mammalian Species No. 34:1-4.

Howell, A.B. 1965. Speed in animals, their specializations for running and leaping. Hafner Publishing Company, New York.

Orr, R.T. 1940. The rabbits of California. Occasional papers of the California Academy of Sciences, XIX. 207 pp.