| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Naturalist's Almanac Naturalist's Almanac October
Sliding through straw-colored dry grasses at the tail end of summer, the tan gopher snake can be surprisingly difficult to spot. Even the characteristic dark red to black saddles running the length of its body work to its advantage, breaking up the animal's outline and blending it into a backdrop of shadowy stems. But if you get too close, this snake will hiss loudly and vibrate its tail in the dry vegetation. Its imitation of a rattlesnake is convincung enough to make most intruders jump back in fear. Though nonvenomous, this gopher snake has earned the nickname "bullsnake" because it will defend itself aggressively with repeated strikes. In October it begins looking for burrows in which to hibernate; even newly-hatched young snakes go straight into hibernation without feeding for the first year of their lives.
In late summer the fir forests of the Sierra Nevada take on a distinct lilac hue as the annual crop of cones ripens. Unlike other conifers, which drop their heavy cones to the ground, red and other true firs hold onto their cones until they disintegrate. But the word disintegrate implies slow decay, when in fact the nine-inch-long, purplish fir cones explode with the vigor of a botanical grenade. The trick helps toss seeds far from the tree, where passing winds can carry them away. When the cones begin dropping their scales and scattering seeds, the spectacle can be intensely beautiful. John Muir wrote that the seeds "mottle the air like flocks of butterflies" as they drift on lustrous rose-colored wings.
After one to five years roaming the open ocean and building powerful muscles, Chinook salmon are finally ready to return to the streams of their birth. Taking advantage of rivers swollen by fall rainstorms, these fish tackle swift currents and countless obstacles with relentless drive. All across northern California, in waterways ranging from tiny riffles to surging rivers, they gather to lay their eggs on silt-free gravel bars where currents keep the eggs cool and oxygenated. Each stream hosts a unique run of salmon with a calendar and spawning strategy adapted to local conditions. If a stream is disturbed by too much human activity, a distinctive genetic strain of salmon may be lost. Once numbering in the millions, salmon populations have plummeted due to overfishing, dams blocking access to spawning grounds, and channel clearing. Many runs are now extinct or have been reduced to only a few dozen adults that return each fall.
On brushy hillsides throughout California, one chaparral
tree is shouting for attention this month. The berries of toyon-also
popularly known as Christmas berry-are changing from orange to a startling
shade of brilliant red. Though toyon berries are eaten by humans, the
tree's call goes out to robins, waxwings, and other birds that have been
waiting for just the right moment to harvest this bounteous feast. During
the ripening process, the toyon locks two protective chemicals in separate
tissues within each berry. Even a tentative nibble from a curious bird
breaks the cell walls, allowing the compounds to mix and form highly toxic
cyanide gas. Once its seeds are ripe, however, the toyon withdraws the
chemicals from its berries and announces the change by producing red pigments.
Within the next few days, the entire crop of berries may be harvested
by eager birds who relish the fruit. In exchange, there's a good chance
they will excrete the seeds in new locations. December
Deciduous forests can be a dreary sight in the depths of winter; there's hardly a hint of greenery, leaves have long since fallen, and the bare branches look sullen. But around coastal streams and wet areas, white alders add a distinctly festive air when their pendulous yellow-green catkins emerge. Drooping from every branch tip, these elegant seven-inch catkins are technically male flowers that disperse pollen as they open, while female flowers appear in the shape of small, brown, woody conelike structures. By appearing in midwinter, after leaf drop, alders ensure that the wind blows through open branches, dispersing their microscopic pollen grains to maximum effect. Alders play an important role in forest dynamics by transforming atmospheric nitrogen into a form usable by plants and animals.
Of all the animals hibernating through the long, cold days of winter, none is more of a surprise than the common poorwill. In fact, it wasn't until 1946 that renowned desert naturalist Edmund C. Jaeger discovered one of these towhee-sized birds sleeping in a rock cavity in the mountains east of Los Angeles. Until then, biologists didn't even suspect that birds could hibernate, though the Hopi knew the poorwill as holchko-the sleeping one. Poorwills, however, have an astonishing ability to cut their oxygen use by 97 percent and survive the winter on just ten grams of stored fat. Their body temperatures may dip from over 100 °F when active to a clammy 41 °F when dormant, but on sunny days poorwills can rouse themselves to grab a quick snack of airborne insects. This feat requires the poorwill to fly at a lower body temperature than any other bird. Poorwills were once thought to migrate south for winter, but reports of them calling in the middle of winter as far north as Sonoma and Shasta counties suggests that many might remain to hibernate throughout California.
David Lukas leads natural history tours and programs in the Bay Area. He can be reached at davidlukas@earthlink.net |
