| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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naturalist's Almanac What to Look for this Summer July
After several months of stealthy growth, the parasitic plant known as dodder becomes quickly evident by midsummer in a variety of habitats throughout California. Resembling a chaotic mass of orange spaghetti thrown on top of other plants, dodder is cursed with nicknames like "devil's guts" and "hellweed" because it destroys some $30 million in agricultural crops each summer. It arises in late spring from a seed no larger than the period at the end of this sentence. Once sprouted, dodder doesn't send out roots but rather a leafless tendril that snakes across the ground. Twining vigorously upward as soon as it touches another plant, the tendril latches on with ferocious suckers that drain nutrients and water from the host's tissues. Growing several inches a day, dodder becomes a dense mat of interlinking vines up to ten feet across. A mature dodder will be covered with thousands of tiny bell-shaped flowers. These produce seeds that can survive up to 30 years while waiting to germinate.
Another addition to the summer parade of strange species is aptly named watermelon snow. Familiar to anyone who ventures into the mountains, this odd alga produces the characteristic pinkish hue of lingering snowbanks at high elevations. Distributed as spores by the wind, this microorganism hatches into four "daughter cells" that swim to the surface of melting snow in early summer. Although the cells have light-sensitive eyespots more common to animals, they also possess chlorophyll, enabling them to feed on sunlight as well as on nutrients in windblown dust. Each cell also contains a tiny speck of red pigment that absorbs the sun's heat like a miniature oven, increasing the cell's metabolism. By midsummer, the cells become increasingly concentrated, to the point where passing hikers may notice their red color. Worldwide, snowfield algae may be abundant enough to play an important role in consuming greenhouse gases. On top of that, they also anchor a surprisingly diverse food web in snow as a staple for creatures like snow worms, protozoans, spiders, and insects. August
Patient observers will notice a subtle change in the behavior of male mule deer at this time of year. For months the males have been eating steadily, lying low, and safeguarding their antlers. Deer antlers are among the fastest growing tissues known, lengthening an average one to two inches a week, yet are fragile and easily broken in their early growing stages. Males with the largest racks will be the most successful during the breeding season, so it's imperative that bucks protect these velvet-covered weapons as they grow. By August, the antlers begin hardening as their blood vessel-filled velvet begins to dry and slough off. Males begin vigorously rubbing their antlers against shrubs and saplings to get the velvet off as quickly as possible. Once an antler hardens, it does not become inert: it is actually living bone. There is evidence that a functioning vascular system keeps the antler "moist" to better absorb the crash of an opponent's rack.
From late summer into autumn the ocean sunfish, or mola, can be readily found by boaters as these fish congregate in nearshore waters. There, it is often observed lying on its side and basking in the warm sun (hence its common name) while gulls pick off its external parasites. Looking more like a gigantic, 11-foot-wide lima bean than a typical fish, this odd creature is the earth's largest bony fish and can weigh in at up to 5,000 pounds. Much of the year the sunfish floats languidly with the ocean currents, apparently doing little to control its direction. It may even die if currents carry it into chilly waters. Instead of scales, sunfish have a leathery six-inch-thick skin for protection. In Monterey Bay and other places, sea lions may nip off a sunfish's fins, then batter their helpless meal for hours. Another problem for sunfish congregating near shore is getting tangled in fishing nets. Off the California coast they may represent up to 25 percent of the bycatch in drift gillnets, a number that may rise to 90 percent in the Mediterranean Sea. September
The Pacific yew is a graceful, drooping understory tree found in the moist forests of northern California. Though it strongly resembles a conifer, with rows of linear pointed needles on its branches, the yew is considered a "taxad" because its female structures are not held in woody cones but in fleshy, fruitlike structures called arils. By September, the seed-bearing arils are reminiscent of juicy huckleberries ripening to a bright red. The bright color works like a flag in the dark forest understory, attracting seed-dispersing songbirds. Though the arils are tasty, the same can't be said for the tree's seeds and foliage. These bitter and highly toxic tissues contain potent alkaloids discovered in the late 1960s to possess powerful anticancer properties. The find instantly elevated the status of what was formerly considered a "trash tree" by foresters, and led to the harvest of the largest trees to produce the cancer drug taxol. Luckily, demand for Pacific yews has tapered off slightly with the development of synthetic alternatives.
Late in the summer of their tenth year, male tarantulas leave the security of their burrows on a quest to mate. It's a journey fraught with danger. First the male must call a female from her burrow by plucking on her web like a captured insect. When she rushes forth to claim her meal, he holds her fangs at bay with specially designed hooks on his legs. At the same time, he must dart in to insert his sperm before attempting a quick getaway. Unlucky males are eaten, but some escape to seek a second mating or to die on a cold autumn night. Females live up to 25 years.
David Lukas leads natural history tours and programs in the Bay Area. He can be reached at david@naturalists-in-action.com |
