Where to See Animals on the Move
From manatees and monarchs to leopard frogs and ladybugs, here’s a guide to experiencing some of the most dramatic and unusual wildlife migrations in the country
- Doug Stewart
- Oct 01, 2004
LOOKING LIKE WALKING helmets, horseshoe crabs swarm a New Jersey beach along Delaware Bay for spring spawning.
OTHER THAN BIRDS AND BUGS, animals in the wild are awfully furtive, from humankind's point of view. They hide in burrows, prowl around at night and favor remote areas where people aren't apt to intrude. The only time we're likely to see wild animals in large numbers is when they migrate.
The definition of "migration" varies from one biologist to another. To some, migration is a seasonal back-and-forth journey between summer and winter habitat. It can also refer to daily round-trips, such as the movement of plankton between the ocean's depths and its surface. Some scientists use the term to describe any large-scale population movement, even a one-time trip by animals fleeing a drought or looking for better forage.
The following examples of migration in the Lower 48 are not all the predictable fall and spring round-trips that birds have led us to expect. Nor are they random dispersals or exploratory movements. But in each case, large numbers of animals in a given species come out into the open and head for new territory—giving us a chance to see them. Their migrations are triggered by a need for better opportunities of one kind or another. Perhaps, like salmon, they're seeking freshwater streams for spawning. Perhaps, like horseshoe crabs, they're after a good egg-laying site. Or perhaps, like pronghorn and manatees, they're mainly trying to stay ahead of inhospitable weather.
Longest Insect Migration
The prize for longest insect odyssey goes to Africa’s desert locust, which can migrate across 3,000 miles in only two months.
The migrations of birds across continents and seas both mystify and delight us. But the movements of many other species, while maybe more subtle or even secretive, offer the patient wildlife enthusiast a chance to see another aspect of one of nature's most mysterious activities. With a little planning, you will find that these lesser-known animal movements offer as much thrill, excitement and potential for awe as do the more-familiar migrations that shift across the skies.
The annual invasion of the beaches of Delaware Bay, particularly along Cape May, New Jersey, by horseshoe crabs is one of nature's grand spectacles. These arthropods—more closely related to spiders than to crabs—spend most of their lives on the Continental Shelf. But during the two full moons and two new moons in May and June, when the tides are highest, they crawl ashore up and down the Atlantic seaboard. With their armorlike shells and whip-shaped tails, they advance ominously across the sands like an amphibious tank corps, although they're perfectly harmless to humans.
"It's really predictable," says biologist Peter Himchak of the New Jersey Division of Fish and Wildlife. A half hour before these four high tides, horseshoe crabs start coming out of the water by the thousands. You can almost hear the background music from Jaws. You just stand there, and before you know it they're all around your ankles."
The slow-motion frenzy of egg-laying females and egg-fertilizing males is best witnessed during a nighttime tide. During the day, flocks of famished migratory birds such as red knots and sanderlings descend on the beaches. For many of them, Delaware Bay is the only place they touch down during their flight from South America to the Arctic. The birds come to gorge on the billions of horseshoe crab eggs saturating the sand. To avoid interfering with this vital pit stop, it's best to bring binoculars to watch the action from viewing platforms set back from the bay's many beaches.
LADYBIRD BEETLES blanket the rocky surfaces of an Arizona mountain slope as they gather to winter at high elevations in the Southwest. In California's High Sierras, they form layers so thick that their warmth melts snow. In spring, they move out to feed on wildflowers in dry valleys.
If you believe ladybugs are good luck, you can find a lifetime's worth of good fortune in mountains all across Arizona and the Southwest, as well as California. The familiar six-spotted, orange-winged convergent ladybug, or ladybird, beetle is a voracious predator of aphids. In the dry valleys of the Southwest each spring, newly hatched ladybugs feed on the aphids found on wildflowers and other annuals. By May, with the plants drying up and the aphids disappearing, the hungry ladybugs fly up into the mountains.
When they arrive, they're no longer so choosy about their diet. "They're very aggressive," says entomologist Carl Olson of the University of Arizona. "They land on anything and start chewing: people, plants or pollen. It's funny—people say, 'Oh, ladybugs are so cute.' But not up in the mountains the first week of May."
The preferred ladybug meal is pollen, with which they stuff themselves in order to build up fat reserves for winter. In fall, they move to overwintering sites, typically on nearby mountain slopes. Individually, a ladybug is a tiny, jewel-like creature, but when they gather by the millions, they coat boulders and tree trunks in motionless blankets of orange. You would think a bizarre cloudburst had just drenched the terrain and everything in it in orange paint. The hibernating beetles are a popular attraction for mountain hikers. Mount Wrightson in southeastern Arizona even has a six-mile Ladybug Trail. In California's High Sierras, the beds can be so thick that their warmth melts snow.
COHO SALMON, moving upstream in silvery hordes to spawn in autumn, can be seen at various points along Washington rivers.
Although most of the Cedar River flows through Greater Seattle, Washington, the waterway offers attractions rarely found in a metropolitan setting. Each fall, King County naturalist Polly Freeman organizes salmon-spotting volunteers as part of a four-weekend program called the Cedar River Salmon Journey. The first of four viewing sites along the river is next to the public library in Renton, just outside Seattle. "This is not backwoods Alaska," Freeman says. "Renton is a city of 40,000. But you can return a book to the library, then look over the railing outside and see salmon spawning. That's way cool."
Pacific salmon arrive in late spring and summer from Puget Sound and pass through Seattle's Hiram M. Chittenden Locks to get to Lake Washington and the rivers where they were born and will die. At the U.S. Army Corps of Engineers' visitors center at the locks, you can watch through large underwater windows as sockeye, chinook and coho salmon negotiate the giant fish ladder.
The salmon at this point are beginning a hormone-driven death run. Once they return to fresh water, they stop eating, their backs become humped and their jaws hooked. After thrashing their way upstream in a desperate race to spawn, their once sleek and silvery bodies give out. Dead salmon soon litter the shallows, food for birds and other animals.
The Pacific gray whale's journey between winter and summer waters ranks among the longest of any mammal, as far as 14,000 miles round-trip.
A major sockeye run is expected in late October and early November this year, and Freeman is excited. "Salmon are incredibly charismatic. When they spawn, they turn a beautful red color that's easy to see." Watching them fight their way upstream to breed is inspiring, she adds. "It sounds hokey, but you can't help but urge them on: 'Come on! You can do it!'"
Tarantulas don't migrate in the sense of switching habitats from one season to another, but in arid parts of the Southwest such as north Texas in late May and June and again in September, you can—if you're lucky—see these spiders moving purposefully across the dry, mesquite-dotted landscape. The fine, bristling hairs covering their massive bodies—tarantulas grow to a crablike five inches—can sense the vibrations of scurrying prey: lizards, snakes and even small rodents. But when males skitter across the countryside en masse, they're looking for females, not food.
Tarantulas spend most of their lives underground. To find mates, adult males in Texas periodically venture as far as a mile, probably guided by smell. "The males will continually search for mates until they run out of energy or until a female eats them," says Norman Horner, a biologist at Midwestern State University in Wichita Falls. Horner once studied the movements of brown tarantulas that he and a colleague managed to radio-collar.
Exactly when male brown tarantulas go a-roaming seems determined by the weather. Their movements tend to occur after a rain in early morning or late afternoon. Mass sightings are rare but memorable. Arachnologist David Sissom of West Texas A&M University in Canyon recalls braking to a stop on Highway 385 just south of Odessa early one summer morning in 1986. "There were hundreds of tarantulas crossing the road, all moving in the same direction," he says. "For 100 yards or so, there was easily a tarantula every meter or two. It was pretty incredible."
IN SPRING and fall in Texas, travelers might spot numbers of male tarantulas, like this one in Big Bend National Park, seeking females.
NORTHERN leopard frogs, which may be green or brown, leave wintering ponds in huge numbers in spring and return in fall. In parts of Minnesota, their numbers are so large during migration that the amphibians become a traffic hazard.
Northern Leopard Frogs
With its bright green skin spotted with black ovals and its daytime habits, the northern leopard frog is a conspicuous sight across much of the northern United States. Its zany, zigzagging leaps might make it seem a touch uncertain, even scatter-brained. In fact, its unpredictable trajectory is an adaptation to baffle predators. Northern leopard frogs are most noticeable when their populations set out in a jerky mass movement to and from the ponds where they winter below the ice.
"After the tadpoles in a pond metamorphose," says herpetologist James Christiansen of Drake University in Des Moines, Iowa, "the population is extremely dense, and the frogs move out rapidly in the spring." Their destinations, typically within a few hundred yards, are breeding marshes too shallow for fish, which would prey on their offspring. "That dispersal causes the mass appearance of frogs on roads and elsewhere, usually after a rain," Christiansen says. "The number of frogs you see can be huge."
The return mini-migration in fall is even more precipitous, and squashed frogs on roadways become a traffic hazard. To spare their amphibians this fate, naturalists at Minnesota's Baker Park Reserve, 20 miles west of Minneapolis, have embedded five-gallon buckets along a busy road that the frogs try to cross each spring and fall. In what they call a "frog ferry," they periodically lift out the buckets and carefully walk their contents across the road.
Manatees in Florida seas migrate into warmer coastal streams as soon as the water around them starts to feel chilly. "Manatees have a blubber layer only an inch thick, which is less than a whale or a dolphin has," says Joyce Kleen, a wildlife biologist at the Crystal River National Wildlife Refuge, "so if they're in water colder than 68 degrees F, they'll die of hypothermia just as you or I would." Warm springs feeding refuge waters on Florida's Gulf Coast lure some 300 of the roly-poly mammals each winter. In summer, Florida's Gulf Coast manatees disperse as far as Texas. The East Coast population summers as far north as the Carolinas or, in the case of one far-ranging individual, Rhode Island.
Their blubber layer may be thin, but manatees are hardly as svelte as mermaids, which Columbus supposedly mistook them for. Looking like a walrus without tusks, they're rotund, whiskery and slow-moving—almost bovine.
Monarch of the Skies
Monarch butterflies hit speeds up to 30 miles per hour but cannot fly at temperatures below 55 degrees F and become paralyzed under 40 degrees.
Wild manatees congregate at a number of winter sanctuaries on both coasts of Florida. At the Crystal River refuge, boaters and snorkelers can see manatees up close, although visitors must hew to strict guidelines, Kleen says, as the creatures are an endangered species. "You can't proke, prod, ride, grab or surround them or separate a cow and calf. You can touch them with one open hand, but you have to allow the manatee to approach you first."
Which they often do. "They're very curious animals," says Kleen, who has had a 1,000-pound manatee gently mouth her diving mask as she carried out a vegetation survey. No, it's not at all like having your head in a lion's mouth, she says. "Their teeth are way back in their mouths. They're not going to hurt you. They're really gentle giants."
PRONGHORN, migrating between Wyoming's Red Desert and Grand Teton National Park, crowd into a bottleneck near Pinedale, Wyoming.
The Green River Basin in western Wyoming is the stage for the semi-annual pronghorn migration, one of longest migrations of any land mammal in the lower 48 states. Shifting between high mountain meadows in summer and lower, less snowy elevations in winter, pronghorn and their frequent traveling companions, mule deer, may move 170 miles between ranges.
The pronghorn is the Western Hemisphere's fastest land mammal, capable of running in 60-mile-per-hour bursts. Thousands of those in Wyoming, however, find themselves slowed considerably at bottlenecks along their routes. The most notorious of these is Trapper's Point, a half-mile constriction just west of Pinedale. Squeezed by topography, roads, fences and housing, the migrating pronghorn and mule deer alike can bunch up dramatically on one side of Highway 191 before slipping across. The pronghorn, unlike the deer, tend to cross 191 in daylight, when they're easier to see. The fall migration at Trapper's Point usually peaks in early November, and the spring return trip in late April, depending on snow and other weather conditions.
Biologist Fred Lindzey of the Wyoming Cooperative Fish and Wildlife Research Unit notes that archaeologists have found pronghorn remains at Trapper's Point dating back 4,000 to 6,000 years. "Native American hunters long ago probably discovered this was a good spot to lie in wait for pronghorn," Lindzey says. "So it's always been something of a bottleneck—it's just gotten narrower."
On the Oregon coast, whale-watching is something you can do without ever leaving shore. Usually, at the peak of the southbound migration in late December and early January, a gray whale moves past Yaquina Light, near Newport, every two minutes. The enormous mammals can be seen heaving into view like crusty mobile reefs, occasionally waving a giant dripping fluke aloft, body-slamming the ocean's surface in a crash of foam or trumpeting a geyser of spray high into the air.
"The gray whales we see here are migrating between the summer waters where they feed—anywhere from the Bering Sea north into the Arctic Ocean—and their wintering grounds off Baja California, where they calve," says Mike Rivers, an Oregon state park ranger. Rivers trains volunteers for Whale Watching Spoken Here, a state-run program that invites people to watch, count and learn about gray whales from 30 viewing sites up and down the Oregon coast.
Half the females going by in December and January are pregnant. Most of the other half soon will be, after mating in the warm waters off Mexico. In late March, the whales cruise past again heading north.
"Ninety percent of them stay within five miles of shore," Rivers says. Still, five miles is a long way to see, even with binoculars, and even when what you're looking for is a whale measuring 45 feet long and weighing 35 tons. "But when it's clear and the ocean's flat, you sometimes see just one spout after another," Rivers says. Last winter, he saw a group of eight males spouting for three solid minutes. "It looked like one of those steam calliopes at the circus," he says.
THIS PACIFIC gray whale off British Columbia will migrate to Mexican seas. Along the way, it can be spotted from shore.
MONARCH BUTTERFLIES hang like ripe fruit from the leaves of a eucalyptus tree in San Luis Obispo County, California. Though they look as fragile as they are beautiful, these insects can migrate thousands of miles. They roost for the winter at more than 300 sites along the coast of California.
The world's most impressive feat of migration is probably that of the monarch butterfly, which can flutter thousands of miles south from the eastern and central United States to winter in central Mexico. West of the Continental Divide, migrating monarchs fly in a westerly direction to converge on California. Monarchs born before mid-August don't migrate at all and usually die within a month. Monarchs that winter in the United States roost at more than 300 sites along the California coast, from Mendocino County to the Mexican border.
Eucalyptus groves are a popular destination, as their foliage gives the butterflies a cool and protected microclimate, according to David Marriott of the Monarch Program, a San Diego-area organization that enlists volunteers in a statewide monarch count each Thanksgiving. Standing at a roosting spot looking up at hundreds of gold-hued, black-trimmed wings overlapping in a translucent sunlit canopy, you have the sense you're admiring fine artwork. "People sometimes compare it to being in a cathedral with stained-glass windows," Marriott says.
In recent years, hot dry weather in Southern California has kept monarchs from sticking around in their usual numbers. "They come here in October, as they always have, but it's been too warm, so they fly north to spend the winter," Marriott says. Reliable sites for tree-covering clusters of monarchs in California include Pacific Grove near Monterey, Bridges State Park in Santa Cruz and the Ellwood Butterfly Grove in Goleta. At Pismo State Beach near San Luis Obispo, docents are on hand all winter to guide insectophiles.
With their dark, pop-eyed faces and moist, glistening skin daubed with festive yellow spots, spotted salamanders are unfailingly photogenic. Yet in New England, where they're common, the salamanders are rarely seen. "They're usually underground nine months a year, and they only come out at night," explains Jennifer Wiest, a teacher-naturalist at the Hitchcock Center for the Environment in Amherst, Massachusetts.
The best time to see spotted salamanders is on the first warm, rainy night of spring, when all the animals in a population move as far as a mile to temporary wetlands called vernal pools to swim, nuzzle and mate. A two-acre pool can host 5,000 of the creatures. A flashlight with red lens tape is a useful accessory, although salamanders caught in the act tend not to care who's watching.
Although they can stay under water for up to 20 minutes, manatees usually swim near the surface. The species' deepest recorded dive was only 23 feet.
Unfortunately, when the burrows and the wetlands are on opposite sides of a busy street, many of the animals end up as road kill. In 1987, the town of Amherst, with help from the Hitchcock Center, pioneered the use of "eco-tunnels"—actually modified airport runway gutters—to help salamanders get across a busy local road. On the Big Night each spring, scores of people turn out along Henry Street to watch the amphibians make their move.
"The first time I saw them," says Wiest, "I felt I was being transported to the Age of the Dinosaurs, watching these 8-inch-long salamanders inching down the hill and disappearing into the tunnels."
Massachusetts journalist Doug Stewart wrote about butterfly behavior in the April/May issue.