Search This Blog

Friday, August 31, 2012

Backyard Boa

Billie appeared at my doorstep in the heat of the afternoon, her hands cupped firmly together and held against her body.  "I've got a boa," she said.  "It came out of a weedy area I was mowing, and I don't want it to get into the road.  Can we release it in your rock wall?"

By all means.  The elusive rubber boa, Charina bottae, is one of those common and utterly overlooked creatures that echos greater things.  It is the small and nearly invisible cousin of the impressive anacondas, pythons, and boa constrictors, massive snakes large enough to eat small deer and peccaries.  The boa family line has some unusual characteristics among snakes.  The members carry two lungs, rather than the single lung considered adequate by most snake species, and boas retain their eggs in their bodies, giving birth to fully-formed young rather than laying the eggs like many other snakes do.  For the uninitiated, boas hunt by lunging out at unwary animals, encircling their prey in coils of their thick, smooth bodies, and strangling their dinner.

Rubber boa. Photo: J. A. Gervais

But the boa family is probably most noteworthy for another reason: they are snakes with legs.  They still retain the tiny nubs of what were once fully functional limbs.  Both sexes carry small spurs placed along their sides above the vent, used primarily by the males in courtship. 

The northernmost branch of the family ranges into North America in the form of two species, the rosy boa and the rubber boa, which extends up into British Columbia.  These are the poor cousins of the spectacularly patterned and impressively sized South American relatives.  The rosy boa boasts some handsome stripes but its northern cousin, the rubber boa, is notable for its plainness and the fact they occur in a wide variety of habitats although they are rarely noticed.  The body is olive or brown or pinkish, the belly lighter and possibly more shaded with yellow, and there are no lovely patterns of brown or black or green, no rings or stripes or spots or really anything of interest at all.  Their scales are small and very smooth and hardly offer any texture to break the monotony of their skin.  All in all, they are spectacularly uninteresting, other than the chance to see those relict legs that are now reduced to small spurs.

Except for two things: rubber boas have tiny eyes.  And they have thick, knobby tails that are as large as their heads.  With the very fine scales and tiny eyes, you might mistake one for a large fat worm.  The legs are pretty surprising, but they're easy to overlook.

Rubber boa head. Photo: J. A. Gervais

Rubber boas spend much of their time underground, haunting rodent burrows and cracks in the earth, sheltering under appropriate human junk.  They seem to do much of their hunting at night, and they are the scourge of the cozy nests of mice, shrews, and other small mammals.  The snake will eat all of the babies if it can, holding the mother at bay with that thick, knobbed tail.  One report also documents a snake consuming both a mother ensatina salamander and her clutch of eggs, which the salamanders brood until hatching.  These snakes are the real cradle-robbing monsters of nightmares.

 However, the boas themselves are often heavily scarred, and some voles and mice will counter-attack repeatedly to defend their offspring.  They may even kill the attacking snake if the snake is a small one.  Bigger boas will also eat birds if they can catch them, and smaller snakes feed on the eggs of other reptiles.  There are reports of big boas trying to eat smaller ones, although these incidents were seen in captivity.  There's a lot of tabloid-style drama going on out in the fields that we never notice.

Billie put out her hands and slowly opened them so I could see the boa.  It was olive in color, with a yellowy underside, about two feet long, and much more interested in hiding its head and presenting its tail to us than escaping.  The rubber boa is also one of the most docile of snakes, moving slowly and nearly impossible to provoke into biting.  They are far more likely to release musk from their vent to deter rough handling, and need to be harassed to do even that.

Down a mouse hole. Photo: J. A. Gervais

Rubber boas in the northwest breed in early spring.  The spurs are part of the courtship ritual, used primarily by the male snakes, whose spurs are more mobile.  Females' spurs are also more conical in shape, where the male snakes have spurs shaped like hooks.  Adult females are larger than males, with shorter tails, and more tail scarring, possibly because the demands of producing young require more hunting.  Females may not eat the entire summer that they are carrying their young.  Instead they seem to spend as much time as they can keeping their body temperature as high as possible to speed the babies' development and birth.  They will be born in August, not long before temperatures drop and all of the snakes must find sites to spend the winter.

Rubber boas are homebodies, frequently caught over and over in the same small area year after year.  They are also impressively long-lived, perhaps reaching a half-century even in the wild.  Their habit of rarely showing themselves in the open keeps them safely off the roads that take the lives of so many garter and gopher snakes, and helps ensure their reputation as the boa you never knew about living right in your backyard.

We looked the snake over closely but missed seeing the spurs, which I didn't know about at the time.  The snake might well have been a female, whose spurs are hardly larger than her scales and may not even be visible.  We released it in the grass not far from the half-buried line of concrete rubble that runs along the edge of our yard, the remains of an old barn foundation we had recycled into snake habitat.  There are too many mouse droppings in the bike shed.  I hope this snake sticks around.

  •  Dorcas, M. E., and C. E. Peterson. 1998. Daily temperature variation in free-ranging rubber boas. Herpetologica 54(1):88-103.
  • Hoyer, R. F. 1974. Description of a rubber boa (Charina bottae) population from western Oregon. Herpetologica 30(3):275-283.
  • Hoyer, R. F., and G. F. Stewart. 2000. Biology of the rubber boa (Charina bottae) with emphasis on C. b. umbratica. Part I: capture, size, sexual dimorphism, and reproduction. Journal of Herpetology 34(3):348-354.
  • Hoyer, R. F., and G. R. Stewart. 2000.  Biology of the rubber boa (Charina bottae) with emphasis on C. b. umbratica. Part II: diet, antagonists, and predators. Journal of Herpetologica 34(3):354-360.
  • Macey, R. M. 1983. Charina bottae food. Herpetological Review 14(1):19.
  • Peabody, R. B., J. A. Johnson, and E. D. Brodie, Jr. 1975. Intraspecific escape from ingestion of the rubber boa, Charina bottae. Journal of Herpetology 9(2):237.
  • Rodriguez-Robles, J. A., C. J. Bell, and H. W. Greene. 1999. Gape size and evolution of diet in snakes: feeding ecology of erycine boas. Journal of Zoology 248(1):49-58.

Wednesday, August 15, 2012

Groundhog Day on a Bicycle

I've been pretty committed to reducing my carbon footprint for a few years now, spurred by the scientific evidence that suggests that global warming is bringing about severe changes to the planet's climate even faster than we had expected.  I'm not someone who still needs convincing. But I still find that the gap between intention and action can be persistent and pervasive, requiring a large reserve of daily resolve to bridge.

I ride my bicycle to town to my office, and for many of my errands.  I have decided not to be dogmatic about it, allowing trips at night and trips to pick up heavy bags of dog food, livestock feed, or kitty litter to be made in the car. But I continually challenge myself to leave the car in the driveway, and take the bike instead.

I've made it easy on myself by riding a good bicycle, a touring bike outfitted for commuting with fenders, lights, and reflectors.  I've got good bike bags, and a nice rain jacket.  My commute is really a lovely short tour for much of the way if I choose a longer route, and bike lanes or bike paths exist on all but the first three-quarters of a mile of my journey.  The shortest distance to my office is just over five miles, and my office has great secure, dry bicycle parking and a place to hang wet clothing.  In sum, I've got the optimal situation for bicycle commuting.

Still, I find the walk from the front door to the bike shed past the car to be one of the most challenging twenty-five yards I've ever traveled.  The battle goes like this: I'm already behind schedule. It's raining. It's hot. It's cold. I'm really tired today.  I might be coming down with something. If I drove, I could do this errand that is not feasible by bicycle.  Everybody else drives.  Maybe I'm just a freak for caring so much.  Why don't I give myself a break today, and  I'm sure I can come up with a reason why I deserve one.  Meanwhile I'm trudging to the shed, pumping up the tires, and resolutely rolling my bike up the driveway.  Fortunately, I live at the top of a hill, because that easy launch helps overcome the last resistance, and off I go.

I've been surprised at the continual inner battle, despite what I know about the science, the consequences of continuing to carelessly emit carbon into the atmosphere, and the fact that I really do enjoy riding my bicycle.  It helps me realize how much greater the challenge must seem to someone who doesn't have such an ideal commuting situation, or whose job is less amenable to arriving at the office wet or sweaty, and needing to change, can't safely ride at all, or who perhaps doesn't see global warming as an immediate threat.

The daily inner battle has also taught me that I need lots of different arguments to help me push the bike out of the shed.  Sometimes, but not often, pure guilt is a motivator.  It typically doesn't work two days in a row. Who wants to feel guilty?  Of all emotions, I think we're best at managing to avoid this one.  I consider it a tool of last resort.

Sometimes I can get myself going by reminding myself of how much I usually enjoy the ride in to town.  This is true, but  the trouble is that I remember plenty of rides I didn't enjoy, when either bad weather, a negative interaction with a motorist, or too many dead deer carcasses on the side of the road ruined the fun.  Still, on the ride to town and back I have enjoyed some spectacular sunrises, encounters with friends, surprise wildlife sightings, and even fresh blackberries in season.  I almost always feel better after exercising.  This motivator works more often than any other.

I've also found I'm pretty reward motivated, and I'm not above personal bribery.  I keep a package of homemade chocolate biscotti in the freezer at work.  All right, I tell myself, biking burns calories.  Ride in today, carrying all of your gear and with full intention of stopping at the store to buy groceries on the ride home, and you can have TWO cookies on your coffee break.  On a bad day I might need three cookies.  I can always promise myself I'll pedal harder to make up for it.

The final motivator is highly personal, and I don't use this one if I'm already in a difficult mood.  I can remind myself of the latest rash of scientific papers filling in the lines of what we're in for as our atmosphere changes.  The danger here is this can make me angry, and too resentful of other people who don't seem to be spending their free time perusing the latest issue of Nature Climate Change or following Skeptical Science, RealClimate, or Climate Progress, but who might be driving their dog to the forest as I bicycle past them.  This is generally counter-productive.  First, resentment gets you nowhere.  Second, being angry at cars while you're riding a bicycle is very dangerous.

Instead, I have to apply all of this knowledge to view global warming as a direct threat to something I care very deeply about, something I don't want to lose or see destroyed.  I think of the glaciers I've seen that my nieces and nephews never will, or the high mountain forests now under threat from bark beetles and fire.  I think of my nieces' and nephews' future, which won't have the glorious biodiversity and take-it-for-granted planetary life support systems I enjoyed when I was their age.  Most often, I think of a small dune of sand that arcs up just above the waves in the far northwestern Hawaiian Islands.

Hawaiian monk seal and pup, Laysan Island 1991. Photo: J.A. Gervais

It hurts to think of all that is going to be lost, parrotfish and monk seals, tropic birds and albatrosses and sea turtles.  I can at least act to prevent more damage, however mundane and humble and small that action might be.  This will get me on my bicycle even in very cold wind and rain.  However, it is also quite dangerous to ride a bicycle if you are upset.  I try the cookie motivator first. 

The little daily battle in the war on global warming has me thinking that although the action is happening in the atmosphere, the front lines are drawn by our smallest actions, held firm by whatever resolve we can muster. There won't be a conclusive confrontation, some  great climax that once and for all ends the war.  It's going to be a lot more like the movie "Groundhog Day" than D-Day.

I'll continue to engage in the fight with the daily trudge up the driveway, one small act of defiance over and over against too much loss to bear.

Chocolate Biscotti (origin of recipe unknown)

Mix and set aside:
2 cups flour
0.5 cup cocoa powder
1 teaspoon baking soda
1 teaspoon salt

Cream together 1 cup sugar with 3/4 stick (6 tablespoons) of butter.  Add two large eggs, beat together well.  Add 1/2 cup chocolate chips and 1 cup chopped walnuts.

Combine sugar-butter-egg mix with the flour mix.  Divide the batter and pat each half into a log, roughly 2 inches wide, 1 inch high and 12 inches long.  Bake on greased cookie sheet for 35 minutes at 350 degrees F.  Let cool on wire rack completely.  Cut into 3/4" slices and put back in the oven for another 10 minutes.

Make cookies while baking some other item to get the most from the electricity needed.

Metric version:
240 g flour
55 g cocoa powder
5 ml baking soda
5 ml salt
200 g granulated sugar
100 g butter