| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Naturalist's almanac What to Look for This Summer JulyWhen fog settles on the coast, and temperatures ratchet up to unbearable in the Central Valley, it’s time to head to the High Sierra, where snowmelt and sun beget a garden of paradise. In the highest plant zone, the alpine belt, the growing season lasts only 40 to 70 days. Few annuals can sprout, flower, and set seed so quickly, so perennials dominate here. They exploit the brief summer by hugging the ground for warmth and bursting into riotous flower displays to flag down the few hardy insect pollinators that live at these elevations. Alpine plants can respire at cooler temperatures than their lowland neighbors, and they hoard most of their biomass in roots and storage organs which are protected below ground. Two out of California’s five alpine species are found in other mountain ranges or in the polar tundra, a reminder that these plants were once widespread during past ice ages, even at low elevations. Fifteen percent of our alpine species are found only here. These plants probably evolved in place over the past 10 to 15 million years as geologic forces uplifted the hills into high mountains. Nearly a third of California’s four dozen mosquito species thrive in the moist Sierra climate. Among the first to emerge in the spring are the “snow mosquitoes,” a handful of species in the genus Aedes. Various Aedes have specialized to exploit every possible kind of standing or running water. Larvae of one species live in snowmelt pools carpeted with pine needles, others thrive in meadow pools full of dead grasses, some prefer pools loaded with live grass, and one species lives in clear, cold seepage pools above 9,000 feet. “Black snow mosquitoes” hover just overhead in swarms of thousands, attacking hikers from sun-up to twilight. Their larvae develop in pools that are dark with organic soil and decomposing vegetation. AugustLong after most other birds have fledged their young, mourning doves continue to nest through the summer, raising up to six broods a year. Mourning doves are the second most common bird in the U.S. The soothing treble coo of male doves as they call for mates can be heard everywhere in California except the high mountains. Once a pair decides on a nest site, the female settles in while her mate flies in search of building materials. Upon his return, he sits on her back while offering a twig. She accepts these gifts, tucking them into place beneath her, until a rickety nest is eventually constructed. It takes about 14 days for the pair’s two-egg clutch to hatch. Chicks grow rapidly on a diet of crop milk, a nutrient-rich fluid secreted from the crop of both parents, regurgitated, and fed to the young. After only two weeks, the young are feathered and leave the nest. The female is then ready to lay her next clutch. We’re most likely to hear crickets singing in the waning days of summer and into the fall. Most cricket song is produced by males advertising for mates, but some calls are hawkish warnings to fend off competitors, and others arouse females to copulate. Of course, crickets don’t sing at all, but produce their melodies by rubbing a file like appendage at the bottom of one forewing across a ridge that runs along the other. As the temperature rises, the wing rubbing quickens, varying from 4 to over 200 passes per second, depending on the species. A female is attracted to the call of a male only if he’s playing a tempo that matches her temperature. Beneath the fog at the edge of the Pacific Ocean, aggregating anemones start their season of sexual reproduction in mid to late summer. Males and females release sperm and eggs into open water, relying on fate and the currents to unite the two and form tiny larvae that drift off to new homes. Offspring that successfully pioneer new territory later reproduce clonally, pulling themselves in two in tugs-of-war that eventually form colonies of identical anemones. Aggregating anemones are the ones that look like squishy, sand-covered mats carpeting the rocks at low tide. Look closely for the “no-anemone zones” that fringe each clump of these creatures. Clone mates grow peacefully side by side but use clumps of stingers at the bases of their tentacles to fight off competing clones that draw too near. September By the time September rolls around, most mosses that grow on trees in California’s forests have spent months in a dried out, dormant state. On your next hike, clip a few clumps of these dehydrated, brown plants from various trees and throw them into a cup of water when you rest for lunch. Within an hour, many moss species burst back to life, turning green as the gears of photosynthesis start rolling. Tortula princeps is a common moss that grows on oaks. Even after being dried in an oven and stored for years, Tortula mosses can revive within minutes when sprinkled with water.
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Summer 2001
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