| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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Naturalist's Almanac What to look for this Spring April
The shrew-mole is exactly that: a tiny mole cast in the mold of a shrew. This strange animal has forelimbs slightly modified for digging and laterally positioned nostrils. But unlike most moles, this completely blind creature forages aboveground for earthworms in the leaf litter of maples, alders, and dogwoods. To get around, it folds its elongated digits over and walks on the tops of its claws. The habit results in a stately pace quite unlike the quick, jerky movements of shrews. In California, they can be found in the mountains of Northern California and moist coastal forests south to Monterey Bay. Data from other states suggests that they breed around April, and travel in small bands of up to eleven individuals. Day and night, the animals sleep in one to eight minute bouts that punctuate active periods of two to eighteen minutes.
Long before dams and irrigation drained the lifeblood from one of the West’s mightiest rivers, the razorback sucker ruled supreme in the Colorado River system. Once extremely abundant in the river’s lower stretches, this prehistoric fish has been reduced to a few scattered individuals and is no longer considered to have self-sustaining populations within California’s borders. Capable of living more than 50 years, each female produces over 140,000 eggs a year. Luckily, it has no problem surviving in reservoirs—an all-too-common crutch these days. This month, each spawning female should be closely attended by two to twelve males who will follow her through shallow waters waiting to deposit sperm on newly released eggs. Great Blue Herons are breeding in Golden Gate Park, San Francisco. View their nests complete with chicks at Stow Lake on Saturdays from 10 a.m. to 1 p.m through May. Call (415) 876-5220 for details. May
Fish populations are not the only evidence of a great river’s death. One could also look at the disappearance of the great riparian woodlands that once lined the lower Colorado River. Only a tiny fragment of the broad ribbon of 300,000 to 400,000 acres that accompanied the river’s passage through California still remains. In the forest, the songs and courtship of sparrow-sized elf owls are virtually a thing of the past. Famous for nesting in the holes drilled by woodpeckers through saguaro cacti, elf owls also nest in the trunks of old riparian trees. After California’s pre-eminent saguaro stand was lost beneath Laguna Dam, and its riparian forests were whittled away, state elf owl populations plummeted to around twenty birds according to a 1987 survey. Surveys conducted in 1998 and 1999 suggest the owl may be extinct in California. Elf owls can still be heard across the Arizona border at Bill Williams River National Wildlife Refuge, (928) 667-4144.
Heads held high, and large eyes alert for fence lizards, the Alameda whipsnakes of the East Bay hills are on the prowl for both food and mates this month. This threatened subspecies of the California whipsnake has been increasingly squeezed by development, the clearing of their brushy habitat, and predation by domestic housecats. They still hang on in protected chaparral shrublands such as those at Mount Diablo State Park. Despite their striking yellow-orange racing stripes, these soot-black snakes are difficult to observe. Extremely vigilant, they dart off like lightning if disturbed. Often they climb into shrubs and flee so quickly it seems like these five-foot long snakes are falling away from the observer.
Throughout the eastern United States, the ever-popular and colorful American goldfinch breeds in July to take advantage of ripening grass seed crops. But in California’s unique Mediterranean climate, grasses mature earlier in the year and goldfinches correspondingly shift their nesting season into May. Sometimes referred to as wild canaries, brilliant yellow males with black foreheads launch into lively trills and twitters. Meanwhile, females weave cup-shaped nests so fine that they will hold water in a rain. The four to six eggs hatch in about a week and a half, just in time for the fledglings to get their first beakfuls of nutritious seeds.
From the moment it first appeared in North America, Russian thistle was feared as an aggressive invasive. It had already rendered 500-mile stretches of prime Russian farmland unusable. Spreading like wildfire across the West despite frantic proposals to fence off entire states, this woody annual soon entered popular lore, song, and poetry as tumbleweed, an icon of the western landscape. By late summer, the plant dries into a compact globe ranging in size from a basketball to a compact car, and begins rolling about in the winds. Rolling is an ideal way for the plant to disperse its quarter-million seeds, and it’s possible to trace the path of a tumbleweed across a newly plowed field by the line of green shoots that pop up after the first rains. By June, these seedlings have reached their full stature as spiny-leaved adults unpalatable to herbivores. Stay away; they’re capable of causing skin rashes if touched. In clear sandy coastal channels, especially at low tide, it is sometimes possible to spot a bed of sand dollars standing aslant and half-buried on the bottom. For anyone familiar with their white shells washed up on the beach, the living animals are unexpectedly beautiful—purple and soft like velvet from countless cilia and stubby spines. Sand dollar spawning season falls in May and June. All the sand dollars in a bed hold onto their eggs and sperm until one can’t wait any longer, expelling all its gametes in an explosive milky cloud. The event triggers the entire bed to spawn at the same moment. This ensures that the maximum number of fertilizations take place. Free-swimming larvae then drift in the water currents. When they encounter olfactory clues emanating from colonies of adults, the larvae stop swimming and bed down for good.
David Lukas leads natural history tours and programs in the Bay Area. He can be reached at davidlukas@earthlink.net |
