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Monday, November 28, 2011

Leaves in Grass

Our neighbors have gone south for the winter, seeking climates where it does not rain six days out of seven.  They leave by Halloween each year, before the rains have really set in, and return when spring is still early enough that wet cold days are the norm even as the Indian plum sends out graceful arcs of cream-colored flowers.

I've been thinking about communities lately, both ecological and human.  We take it as a given that the natural world is made up of many interconnected pieces, so that no single organism stands by itself.  For some reason, we have a much harder time accepting this view of our own communities, even though it is every bit as true.  This matters, as how we manage the coming enormous upheaval on a planet in rapid climatic transition will depend on how we see each other, and our relationship to both the rest of humanity and to the larger biological community of which we are an indivisible part.

The leaves have fallen in the neighbors' garden, thick enough to smother the grass if they remain there until spring.  I took the dogs and a rake and wheelbarrow and went to work, sweeping up the remnants of last summer's photosynthesis and depositing them in the garden plot.  Leaves are extraordinary.  They do all the work of taking sunlight, which in itself is simply energy, and transforming that energy into actual food- both for the plants, and for nearly all the rest of the non-plant life forms on the planet.  It is a very cool trick.  An even more amazing part of the trick is to shed the biomass when it becomes more of a liability than an asset, first salvaging the good stuff before letting the depleted leaf fall free.  The rest of us get a blaze of colorful glory before the curtain falls and winter takes the stage.

We have an understanding with these neighbors.  In the summer, they allow us to pasture our ewes and lambs on their five-acre pasture, and keep an eye on the water trough.  They've helped us build fences, taught us how to deliver lambs that are too tangled to come out on their own, and loaned us innumerable tools.  They've shared vegetables, gardening knowledge, tips on livestock care, small gifts, and great stories.  They are the sort of neighbors most people only know of through a culture of yesterday. 

In return, we help as we can, share lamb and blueberries and fresh bread, and keep an eye on their place when they go away for the winter.  I rake leaves and I can never quite believe that the summer is really gone, our neighbors are gone, and now there is the winter to be gotten through before we look down the hill and see their lights shining, breaking the darkness with a friendly light that says the neighborhood is as it should be.  The leaves have got to be gathered up first, and given a chance to move through the next stage of the cycle.

Shed leaves are a major component of soil humus, providing food and shelter for all manner of soil organisms.  I leave a fair number of scattered leaves as I rake, so they will provide fodder for the earthworms and enrich the soil that in turn supports the tree.  They'll be long gone by spring, and they are scattered enough so they will not impact the grass.  I use a bamboo rake and a wheelbarrow, because they get the job done while leaving me with the peaceful late fall afternoon, broken by the happy huffing of my dog in hot pursuit of his tennis ball, which I throw between sweeps of the rake, the calls of small flocks of juncos and chickadees, and once the sound of a tree falling in the woods by the creek.  It was wet and windy the day before, and the cycle of renewal incorporates more than just leaves.

I finish before dark, but not before the cold of evening flows in along the creekbed next to the garden, and the sheep start looking expectantly for some alfalfa pellets in their feeder.  Properly done, the afternoon's work will nourish both the human community and the wild one, with no loss to either.  Surely we can find a way forward that truly honors that which we value most.

Friday, November 18, 2011


One of the reasons I love living in western Oregon is that winter brings another season of life rather than a frozen dead spell, when most organisms either flee or hibernate until spring.  A few mammals and birds tough it out where winter brings snow and ice, but the woods are pretty quiet besides the sound of bare branches scraping in the wind.

Here, the tree branches are free of leaves now thanks to some Pacific storms ranting across the coastal mountains.  The branches aren't bare, however.  The forest is turning a new shade of green, one with delicate pale-gray hues, as the lichens unfurl on every small branch and twig of the oaks and maples.  Thick rugs of newly revived liverworts and mosses embrace the trunks and larger branches.  The snakes and lizards have disappeared, but the rough-skinned newts are out, marching along on their rubbery legs as they begin to move toward their breeding pools.

Photo by Miguel Viera, Flickr Creative Commons

The rough-skinned newts, Taricha granulosa, appear when late fall finally eases the harsh seasonal drought with the misty rain.  The newts are both numerous and active during daylight, unlike any of their kin.  They are encountered more often than they are noticed, judging by the number of flattened corpses on the road leading to the forest gate, and sadly, even in the woods where vehicular traffic is replaced by bicycles and walkers.  It isn't always adaptive to look like a somewhat rotten stick when viewed from above.

Rough-skinned newts tend to freeze in place if startled, although they can move along at a good clip if they decide they need to.  They are patient, and will stand motionless in mid-stride for many minutes if disturbed.  Their second line of defense is to curl in a distinctive ring, head thrown back, tail arched toward their throats, exposing their undersides in bright warning.  This dance to avoid being eaten is called the unken reflex, and it is shared among salamanders, toads, and frogs who defend themselves using chemical warfare as a last resort.

Unken reflex.  Photo by Ap2il, Flickr Creative Commons.

In the case of the newt, the bright orange color is backed up by tetrodotoxin, a potent neurotoxin, one shared with the blue-ringed octopus, a few toads, and some fish, most famously the puffer fish.  The Japanese serve a dish called fugu, which ideally offers the adventurous diner tingling lips but if not expertly prepared, leaves the victim paralyzed then dead through respiratory failure.  The Seattle Audubon Society's book Amphibians of the Pacific Northwest(1) reports that people have died from eating newts in the genus Taricha, although they do not reveal the circumstances.

How exactly such a diverse group of organisms have hit upon the same defense strategy is still unclear, although some researchers have suggested that symbiotic relationships with bacteria who synthesize the tetrodotoxin may explain the pattern(2).  Not everyone agrees, however, that this is how the newts acquire their chemical weaponry(3).  All stages of the newt are toxic, and mothers seem to pass on the poison to their eggs.(4)  Individual newts have variable levels of the toxin(5); presumably it is biochemically expensive to manufacture, and you might get by with a less stringent defense if your enemies expect all members of your species are equally bad for the digestion.  The predators, however, are on to the game.  Common garter snakes (Thamnophis sirtalis) have immunity to the poison(6), although they may become toxic themselves from the tetrodotoxin that builds up in their livers after eating several newts(7).  Larval dragonflies will snack on larval newts, and seem able to discriminate the palatable individuals from those best left alone(8).  Ultimately, any strategy is a gamble, and staying alive means playing the odds.

The chemical-defense strategy may not be the best option in this new world dominated by humans.  Cars do not notice unken reflexes, nor do fast-moving bicycles respond to poison.  Newts can live a long time if they avoid tetrodotoxin-resistant snakes and savvy dragonflies.  Like many long-lived species, they reproduce slowly, with few offspring reaching adulthood.  Their populations are poorly equipped to lose many members to novel death traps.  When I find a newt on a road or a popular path, I promptly give it a lift to the other side, hoping it will keep moving away from the ribbon of danger it cannot hope to comprehend. 

In December, we'll begin looking in the drainage ditches and small ponds in our area, hoping to see the graceful, slow dance of the swimming newts as they gather to mate, then lay eggs long before the first buds appear on the trees.

References (for the terminally curious)
(1).Jones, L.L.C., W.P. Leonard, and D.H. Olson, editors.  2005.  Amphibians of the Pacific Northwest.  Seattle Audubon Society, Seattle, WA.
(2). Chau, R., J.A. Kalaitzis, and B.A. Neilan. 2011. On the origins and biosynthesis of tetrodotoxin. Aquatic Toxicology 21(3):131-141.
(3). Lehman, E.M., E.D. Brodie, and E.D. Brodie. 2004. No evidence for an endosymbiotic bacterial origin of the tetrodotoxin in the newt Taricha granulosa. Toxicon 44(3):243-249.
(4). Lehman, E.M. 2005. Tetrodotoxin as a maternally-endowed defense against egg predation in the rough-skinned newt, Taricha granulosa.  Integrative and Comparative Biology 45(6):1032.
(5). Hanifin, C.T., M. Yotsu-Yamashita, T. Yasumoto, E.D. Brodie, and E.D. Brodie.  1999. Toxicity of dangerous prey: variation of tetrodotoxin levels witin and among populations of the newt Taricha granulosa. Journal of Chemical Ecology 25(9):2161-2175.
(6). Brodie, E.D. III, and E.D. Brodie, Jr. 1990. Tetrodotoxin resistance in garter snakes: an evolutionary response of predators to dangerous prey. Evolution 44:651-659.
(7). Williams, B.L., E.D. Brodie, and E.D. Brodie. 2004. A resistant predator and its toxic prey: persistence of newt toxin leads to poisonous (not venemous) snakes. Journal of Chemical Ecology 30(10):1901-1919.
(8).  Gall, B.G., A.N. Stokes, S.S. French, E.A. Schlepphorst, E.D. Brodie, and E.D. Brodie.  2011.  Tetrodotoxin levels in larval and metamorphosed newts (Taricha granulosa) and palatability to predatory dragonflies.  Toxicon 57(7-8):978-983.