| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
|
|
|
|
|
Naturalist's Almanac What to look for this Summer July
A number of animals have developed a specialized mating system called lekking. It’s little more than a dance club for singles, where suitors show off before an audience of prospective partners. Sage grouse are among the most famous lekkers; males strut past interested females and make booming calls with their outrageously inflated throat sacs. In 1975, entomologist Bert Hölldobler made the astonishing discovery of a harvester ant “dancing ground,” with a sea of countless male and female ants boiling over in frenzied courtship. Closer inspection revealed future queen ants flying in by the thousands to join. On landing, each queen is immediately mobbed by suitors. Inseminated queens fly off into the surrounding desert to start new colonies. What Hölldobler found most remarkable is that the ants return each July to the same lekking site. The conical mounds of harvester ants are usually surrounded by an area cleared of all vegetation by the ants’ ceaseless commuting. Look for them in southern California’s deserts and mountains.
Long after the rest of California has gone dry, fertile spring arrives with a flourish in the alpine zone of the Sierra Nevada. Among the best wildflower displays are those found in alpine islands known as nunataks. Too high to have ever been capped or scraped clean by Ice Age glaciers, nunataks have developed deep soil layers and the richest biological diversity in the alpine zone. Foremost among Sierra nunataks is the Dana Plateau of Yosemite National Park, where over half of the 300-plus alpine plant species found in the entire Sierra Nevada can be spotted within one square mile. Only patient observers willing to work on their bellies will fully appreciate the tiny Ivesias, Carexes, Eriogonums, and other plants that populate this area. Faced with extreme climatic conditions, nunatak flora grows just a few inches high—willow trees that normally grow tall enough to hide bears press against the ground in dense mats up here. Viewing this liliputian ecosystem is an exercise well worth the long, steep hike. August
Of North America’s many frogs and toads, Couch’s spadefoot toads are among the best adapted to desert living. They can remain buried in desert soils for up to three years waiting for one heavy summer monsoon. When a cloudburst finally hits with sufficient force, these greenish-yellow toads emerge in unbelievable numbers. Sounding like a stampede of bleating lambs, their deafening choruses fill the night around quickly evaporating breeding ponds. But the mating melee usually lasts only for a single night—after their evening upon the stage, the toads disappear underground until the next breeding season. In California, Couch’s spadefoots are found only in the extreme southeast corner of the state. One good place to seek them is around the Imperial Sand Dunes Recreation Area (760) 337-4400, but ensure that the weather report calls for rain before you go.
Fall can be the most exciting time of year to go birdwatching at Año Nuevo State Reserve, when the park becomes a crossroads for an amazing diversity of birds. By late August, the first arctic-breeding shorebirds appear en route to their southern feeding grounds. At the same time, tropical species such as Manx shearwaters, brown pelicans, Heermann’s gulls, elegant terns, and Xantus’ murrelets wander up the coast to dine on schools of silver anchovies and other small fish. A steady mix of arriving and departing species keeps central coast parks busy until at least November. Año Nuevo State Reserve, (650) 879-2025. September
Among the many species that have settled on California’s Channel Islands, none have diverged so greatly from their mainland cousins as island night lizards. In fact, these black mottled lizards have grown so different after 10 to 40 million years of isolation that scientists have granted them their own genus. Sticking close to rock crevices and never wandering more than ten feet from their daytime sleeping nooks, these six-inch-long lizards are die-hard homebodies. This habit makes their very presence on the barren slopes of San Clemente, San Nicolas, and Santa Barbara Islands somewhat of a mystery. They would be unlikely volunteers for a channel rafting trip on driftwood or fallen trees, as most theories of island colonization propose. Alternatively, the lizards could have been carried offshore on pieces of land torn loose by tectonic activity, a process called vicariant transport. In the absence of competitors or predators, they have not only evolved to gargantuan proportions compared to most night lizards, but also occur in densities that exceed 3,500 lizards per acre. In late summer, broods of four to nine young are born live, ready to start taking care of themselves.
All along the California coast, the plant community known as coastal scrub comes alive this month with coyote brush flowers. So abundant is this durable plant that in many areas it completely dominates its habitat, shading out the understory and excluding other species. In fall, coyote brush becomes heavily laden with clusters of white flowers that buzz with ceaseless insect activity. The flowers lack the petal-like rays of their sunflower family namesake and resemble the buttonlike center of a daisy. Male and female flowers grow on separate plants. After blooming, female flowers transform into puffy sprays of white downy seeds that scatter widely with each gust of wind.
One of the biggest turkey vulture migrations north of Mexico was discovered less than ten years ago in the Kern River Valley east of Bakersfield. Observers now regularly document close to 30,000 vultures, with daily counts reaching as high as 4,500. Celebrate this scavenger at the Kern Valley Vulture Festival, Sept. 26-29 (www.valleywild.org/tvfest.htm) or sign on as a volunteer vulture observer (sanddragon@acninc.net).
David Lukas leads natural history tours and programs in the Bay Area. He can be reached at davidlukas@earthlink.net |
