National Wildlife: November 2005 Archives

Pesticides & Endangered Species

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Poisoning the Imperiled
Three decades after DDT was banned, pesticides still take a toll on the nation's most vulnerable species

Copyright Jessica Snyder Sachs (first published in National Wildlife)

THE BALD EAGLE on Richard Stroud's autopsy table showed the all-too-familiar signs of carbofuran poisoning: talons knotted into fists, legs cocked back against its body, but no signs of traumatic injury or disease. "Basically, the mechanism was death by convulsion," explains Stroud, a veterinary pathologist with the National Fish and Wildlife Forensics Lab in Ashland, Oregon.

Ironically, deadly but short-lived poisons such as carbofuran have come into use largely to replace less acutely toxic but lingering pesticides such as DDT. The devastating effect those earlier pesticides had on birds—especially predatory species such as the bald eagle—inspired Rachel Carson's 1962 manifesto Silent Spring, which in turn helped spur creation of the U.S. Environmental Protection Agency (EPA) in 1970 and passage of the Endangered Species Act three years later.

Yet today, three decades after the act was passed, pesticides remain a threat to the recovery of the nation's endangered plants and animals. The crueler irony, perhaps, is that EPA, the agency charged with assessing pesticide hazards, has no estimate of how many of more than 700 pesticides it has registered pose a hazard to more than 1,260 species listed as threatened or endangered.
By its own admission, the agency has not even tackled a backlog of pesticides that initial studies red-flagged as potentially harmful; these chemicals remain in use pending further evaluation. The number of pesticide victims is equally unknown. "We don't come close to having a handle on all the mortality," says Stroud. "While a dead eagle dropping in a barnyard is hard to miss, most pesticide victims simply disappear."

Toxic by design, the hundreds of pesticides on the U.S. market today include insecticides, rodenticides, herbicides, fungicides and disinfectants. Beneficial, even essential, under some circumstances—protecting an important food crop, for example—their use extends far beyond agriculture to nearly every home, business, school, hospital, park and roadside. Recent studies of major rivers and streams document that virtually all surface waters in the country contain detectable levels of one or more pesticides.
Protecting endangered species from these products is getting more complex: As manufacturers keep bringing new pesticides to market, studies continue to uncover unexpected hazards from those already in widespread use.

Modern pesticides threaten nontarget plants and animals differently than those that caused a public uproar three decades ago."Where once we had a problem with organochlorine pesticides that produced eggshell thinning, today we have poisons that acutely and fatally affect the nervous system by blocking nerve transmission," says Stroud. One example is a class of pesticides, including carbofuran, called cholinesterase inhibitors.

Even more problematic may be the widespread use of herbicides and insecticides known as endocrine disrupters. These compounds work by blocking crucial biochemical pathways such as those used by plants and fungi to form waxy cuticles or by molting insects to form hard chitin skin. In vertebrates from frogs to humans, however, these chemicals interfere with the development of reproductive organs, leading to gross deformities and, in humans at least, cancer.

Some pesticides have killed endangered species outright. In central California, for example, Stroud has seen several San Joaquin kit foxes die of internal hemorrhages after eating poisoned rats. Stands of Texas poppy mallow and neces river rose mallow are occasionally razed when landowners clear brush with herbicides that target broad-leaved plants. And scores of piping plovers have died from seizures over the past few years after their habitat was sprayed with the insecticide fenthion in an effort to eradicate mosquitoes.

Even sublethal pesticide doses take a toll. "When life is a fight for survival, imagine how something as simple as a tremendous headache will set you up for increased predation," notes Stroud. "Because we only see the acute deaths, we don't pick up the chronic problems associated with pesticide exposure." Scientists have discovered endangered animals that suffer abnormal development, deformities, lowered fertility, impaired senses or increased susceptibility to predation and disease when they're exposed to even trace amounts of certain pesticides or their residues.

Take the mysterious global decline of amphibians. Though the problem likely stems from several factors, including habitat loss, Gary Fellers, a research biologist with the U.S. Geological Survey (USGS), and his colleagues have linked reduced tadpole survival and frog deformities to organophosphate insecticides such as diazinon, chlorpyrifos and malathion. In follow-up lab studies, another USGS researcher, Deborah Cowman, found that these insecticides cause genetic damage, which likely results in the increased incidence of death and deformities such as absent or extra hind limbs. Other research has shown that endocrine-disrupter pesticides, such as the widely used herbicide atrazine, cause sexual abnormalities in frogs exposed to trace amounts as low as one part per 10 billion.

Even amphibians in apparently pristine areas have suffered. In California's snow-capped Sierra Nevada, for example, Fellers has spent more than a decade studying crashing populations of frogs and toads. "We're finding high levels of a lot of pesticides," he says of habitat on the western slope. Fellers believes the contaminants are carried in by wind from the central valley, where farmers apply roughly 156 million pounds of pesticides a year. Victims include the mountain yellow-legged frog and the California red-legged frog. The largest native frogs west of the Continental Divide, redlegs were so common in the early 1900s that they featured prominently on restaurant menus and in jumping contests such as that made famous by Mark Twain's "The Celebrated Jumping Frog of Calaveras County." Today few people have witnessed the frog's spectacular leap, and the species continues to decline.

Not surprisingly, frogs and other amphibians show a special vulnerability to any poison dissolved in their watery habitats. "They're like environmental sponges," says Fellers. A similar vulnerability can be seen in fish such as the Northwest's 26 threatened and endangered populations of Pacific salmon, a group that includes migrating coho, chinook, chum, sockeye and steelhead.

"While we sometimes see pesticides kill these fish outright, I'd say most of our scientific concerns point to sublethal effects," says research zoologist Nat Scholz of the National Oceanic and Atmospheric Administration's Northwest Fisheries Science Center. As an example, Scholz describes a remarkable behavior normally seen when a predator such as a kingfisher strikes a juvenile Pacific salmon: Young salmon downstream of the attack instinctively stop feeding and drop motionless to the bottom to avoid the same fate. They're detecting a special alarm scent, or pheromone, released from the wounded animal's skin cells, Scholz explains.

That doesn't happen, though, when trace amounts of copper-based fungicides and algaecides leach into stream waters from pressure-treated wood pilings, irrigation canals or crop fields. Laboratory studies by Scholz and others have shown that copper impairs the salmon's olfactory nervous system, or sense of smell. In addition to avoiding predators, salmon rely on their keen noses to navigate home to their spawning grounds and to successfully time the laying and fertilization of their eggs. And copper pesticides, though widespread, account for just a handful of more than 50 pesticides found in Northwestern salmon streams.

Indirect harm, sometimes missed by EPA tests, is another problem. Endangered plants, for example, can be devastated not only by direct contact with an herbicide, but also indirectly by insecticides that wipe out local populations of pollinators. "A lot of endangered plants depend on specific species of pollinators," notes botanist Jackie Poole of the Texas Parks and Wildlife Department. Animals can likewise suffer indirect harm. In addition to poisoned kit foxes, Stroud has seen multiple instances of bald eagles that died after feasting on famphur-poisoned starlings.

Another regulatory weakness stems from the unknown effects of hundreds of so-called inert ingredients contained in commercial pesticide formulas. EPA requires manufacturers to safety test only "active" ingredients—the chemicals directly responsible for killing the targeted insect, plant, fungus or microbe—but not the emulsifiers, binders, spreading agents and other chemicals that contribute to the pesticide's effectiveness. Of special concern are additives known as adjuvants or synergists, which boost the active ingredient's toxicity.

"While a variety of pesticide products share the same active ingredient, these other ingredients give them different actions and potencies," explains Peter deFur, an environmental toxicologist with Virginia Commonwealth University's Center for Environmental Studies and a scientific advisor on federal committees looking at endocrine-disrupter pesticides. "Our message has been loud and clear," says deFur. "The EPA needs to look at pesticides as they are used—as chemical mixtures." Exposure to combinations of different pesticides with similar active ingredients is a similar often overlooked danger.

New research also shows that certain pesticides become harmful at ultralow doses, far below the levels where toxicologists normally stop testing. "If you stop testing when you see no mortality or only test for a few days, you'll entirely miss these effects," says deFur. Yet short-term tests for deadly effects remain the standard for pesticide registration.

DeFur's own research explores the impact of pesticide-contaminated farm runoff on Virginia's many endangered freshwater invertebrates, including fist-sized pearly mussels and "pig toes." He has found that endocrine-disrupting pesticides such as atrazine and dimlin can directly interfere with the formation of the animals' shells. Worsening the problem, other pesticides kill local populations of fish that harbor the mussels' free-swimming larvae inside their gills.

To prevent harm to such vulnerable plants and animals, EPA is required by law to consult with federal wildlife agencies—NOAA Fisheries for marine and anadromous species and the U.S. Fish and Wildlife Service (FWS) for others—on the potential impact of pesticides on endangered and threatened species. Yet the agency faces a large and growing backlog of products awaiting such consultations, including more than 50 that scientists have identified as potentially harmful to listed plants and animals. For their part, the federal wildlife services seldom clamor to fulfill their own legal obligation under the act: to ensure that no action by a federal agency (including pesticide approval) hampers endangered species recovery. NOAA Fisheries oversees 55 listed species, including all endangered salmon, while FWS manages more than a thousand.

To help slash the backlog, the administration has proposed a rule change that would limit EPA's requirement to consult with wildlife services to only those pesticides that the agency has deemed "likely" to adversely affect listed plants and animals. In effect, the move would shield from the agencies' scrutiny any product EPA deems a "possible but not likely" hazard.

When federal agencies released the proposal for public comment in early 2003, they received a flood of responses. Overwhelmingly, pesticide, industry and farming groups voiced support. Citing EPA's poor track record at enforcing endangered species protections, conservationists, water boards and biologists objected. "This proposed rulemaking change is clearly de-signed to put pesticide approvals on a fast track, with less time to look for impacts on wildlife," says NWF senior counsel John Kostyack. "Historically, EPA has always given short shrift to wildlife," he adds.

Worsening this crisis of trust, advocacy groups have caught EPA consulting with pesticide manufacturers behind closed doors, says veterinarian Patti Bright, director of the American Bird Conservancy's pesticides campaign. Through Freedom of Information Act requests, the conservancy garnered memos and e-mail showing a pattern of industry making changes in the agency's initial assessments, she says. "In one instance, the industry had the agency scrub anything that referred to eagles in an assessment of rat poisons that had been shown to kill threatened bald eagles and golden eagles, as well as endangered San Joaquin kit foxes."

Bright also cites a pattern of EPA routinely granting "emergency exemptions" allowing growers to use highly toxic pesticides such as carbofuran in situations known to kill wildlife, including endangered songbirds. "When we see these emergency exemptions being granted year after year going back to 1995, it forces us to conclude that these are not emergency situations at all," she argues. Bright and others point to the wisdom of the Endangered Species Act and its clearly stated requirement that EPA, with its staff of pesticide specialists, consult with wildlife biologists at FWS and NOAA Fisheries.

The real issue, say observers on both sides of the argument, is woefully inadequate funding. "Right now, no agency or service has the kind of resources needed to do these crucial endangered species assessments," says Kostyack. "We have limited staff," agrees EPA's Arthur-Jean Williams with deadpan understatement. Responsible for running the endangered species program under the agency's pesticide office, Williams recently received permission to double her staff of scientists—from three to six. Such limitations continue to slow progress on endangered species protections.

As a veteran of EPA's scientific advisory panels, deFur recalls the years of "hemming and hawing" over the use of just one particularly troublesome pesticide formula—the granular form of the insecticide carbofuran, which resulted in widespread deaths of endangered songbirds and their predators. "Nothing happened until, one day, a carbofuran-poisoned bald eagle turned up on Senator John Warner's doorstep," deFur recalls. Virtually overnight, the pesticide's granular form was pulled from the market.

"Unfortunately," says deFur, "we're not always going to have such a charismatic victim to grab attention."

Jessica Snyder Sachs is the author of Corpse: Nature, Forensics, and the Struggle to Pinpoint Time of Death (Perseus, 2001).

Wildlife Corridors

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Seeking Safe Passage
Scientists are discovering the benefits of protecting corridors that connect isolated wildlife habitats

Copyright Jessica Snyder Sachs
(first published in National Wildlife)

LINE AFTER SKINNY LINE of pine trees flicker past the truck window like so many rows of corn, as U.S. Forest Service biologist David Dorman patrols the sandy roads of northern Florida’s remote Pinhook Swamp. These fast-growing slash pines, like the spiky saw palmetto weeds matted between them, are native species, notes the scientist. But their regimented and crowded condition is anything but natural—the result of 150 years of logging, draining and machine planting.


A far different landscape emerges as Dorman begins to talk about the long-term future, when restoration of the Pinhook’s natural water flow and seasonal fires brings back a “pre-European” ecosystem of blackwater cypress swamp dotted with flatwoods of longleaf pine and burn-resistant grasses. “A hundred years from now, you’re going to be able to drop a minnow at the top of the Okefenokee Swamp [60 miles north] and see it swim all the way to me and keep on going,” says Dorman.

Nature's Natural Highways
Some of the most passionate advocates of Macon, Georgia’s new Ocmulgee Heritage Greenway are bird-watchers who come to the river each spring and fall. “So many Neotropical migrants pass through here,” says Rose Payne, a resident of nearby Musella. “Scarlet tanagers, black-throated blue warblers, rose-breasted grosbeaks, even turkey vultures.” Indeed, waterways such as the Platte River have always served as natural highways for migrating birds, their wetlands providing vital rest and refueling stops for journeys of hundreds to tens of thousands of miles. The Mississippi Flyway alone conducts millions of birds of more than 300 species to and from their summer and winter homes each year. Beneath their surface, North America’s rivers likewise provide corridors for hundreds of fish species on their own seasonal migrations.

Unfortunately for wildlife, civilization also feels this draw to the water’s edge. As a result, more than two centuries of dumping, development and dam building have altered many North American rivers in ways that hinder and block wildlife movement.

Though serious problems persist, the good news is that conservation groups and government agencies have begun to work together to restore safe passages along some of the nation’s rivers and their surrounding habitats. Four years ago, the U.S. Fish and Wildlife Service initiated the National Fish Passage Program to help local communities and agencies restore natural flows and fish migrations by removing or bypassing man-made barriers such as dams and poorly placed culverts. That same year, the National Wildlife Federation released Higher Ground, a report encouraging responsible floodplain management by steering new development away from flood-prone areas and restoring these vital wetlands through voluntary property buyouts. The report resonated strongly in the wake of the multibillion-dollar damage of the Midwest spring floods of 1997.

“What we’ve seen in the last few years has been revolutionary, a sea change of thinking,” says the report’s author, NWF Resource Specialist David Conrad. “Across the country we’re seeing communities identifying ways of rolling back development away from rivers and restoring the natural functions of floodplains.”

After the 1997 floods in Grand Forks, North Dakota, and East Grand Forks, Minnesota, for example, city officials created a 2,000-acre open space area between the towns along the Red and Red Lake Rivers. The Greater Grand Forks Greenway now protects residents from future floods, restores ecological stability to the river corridor, and connects wilderness areas on both sides of this twin-city metropolitan area.—Jessica Snyder Sachs

Such future prospects don’t come cheap. In a celebrated buyout last year, nearly 60,000 acres of this 170,000-acre swamp passed from private to public ownership at a cost of $60 million. The rangers of nearby Osceola National Forest will now manage the land with the primary intent of restoring native habitat, switching from a 15- to 20-year cycle of clear-cutting to a 100- to 120-year cycle of selective harvest. Government land managers estimate they need another $116 million to buy the remaining prime timberland from private interests.

The patch-by-patch buyout of the Pinhook Swamp means far more to conservationists, however, than restoration of an isolated habitat. The swamp forms a perfect puzzle piece connecting the even larger wetlands of the Okefenokee National Wildlife Refuge in southern Georgia with the pine flatwoods and cypress swamps of the Osceola National Forest in northern Florida.

“The acquisition of the Pinhook will give us the largest protected wildlife corridor east of the Mississippi River,” says Andrew Schock, director of the National Wildlife Federation’s Southeastern Natural Resource Center. “We’re especially pleased about the land purchases last year, but there is still a lot of work to be done.”

Conservationists have championed the Pinhook as a vital travel route for Osceola’s population of Florida black bear, a subspecies that is considered threatened in the Sunshine State. The national forest being too small to sustain them, the bears often wander north through the Pinhook and into the Okefenokee, searching for food and mates while avoiding the towns and highways that hem them in on all other sides.

For his part, Dorman is more excited about connecting populations of less charismatic species, such as the threatened flatwoods salamander and the countless insects, worms and mollusks awaiting discovery in the Pinhook’s little-studied ecosystem. “A pine plantation doesn’t pose much of an obstacle to a bear that can travel 30 miles in a single night,” he explains. “But drain even 100 yards of swamp and you’ve thrown up a roadblock between populations of amphibians and invertebrates on either side.”

Less than 150 miles away, another biologist shares a similar vision as he stands on a sandbar of Georgia’s Ocmulgee River. “We have an interesting bottleneck here, in that the wildlife corridor between Georgia’s coastal plain and its piedmont runs straight through downtown Macon,” says Brian Rood, chair of Environmental Science at nearby Mercer University. Hoping to reestablish this corridor, Rood has thrown his scientific support behind a local plan to establish a 35-mile-long riverbank greenway that would run through the city and connect national wildlife refuges on either side. The project would also create a recreation area for Macon’s residents.

At first blush, efforts to save a vast, remote swampland and those to establish an urban recreational greenway would seem to have little in common. Yet both are being championed as vital wildlife “corridors”—among the most widely debated topics in wildlife conservation efforts today. Where once environmental activists concentrated on protecting isolated parcels of prime habitat, a new drive is for “connectivity.” Indeed, there is something intuitively appealing about the concept of reconnecting a modern landscape fragmented by urban sprawl and endless highway.

Few places illustrate this fragmentation as well as America’s most populous state, California, where last year interest in wildlife corridors drew more than 160 scientists, conservationists and land managers for a one-day mapping marathon. The result: a 100-page atlas and report identifying more than 300 “linkages” needing immediate protection across the state. The findings, published last summer, won the endorsement of California’s director of natural resources, who vowed to make the corridors her agency’s “top priority.” Already, California authorities have spent more than $20 million to acquire the first 2 of 232 identified corridors—one a ranch in the mountains behind San Diego, the other a canyon in Los Angeles.

But not everyone is cheering such efforts. “Serious conservation isn’t as easy as skinny linkages between insufficient natural areas,” argues University of Tennessee biologist Daniel Simberloff. “Clearly, something about the concept of wildlife corridors has ignited public interest, and that’s a good thing. But we don’t want people thinking they’re preserving nature when they’re really not.”

Critics such as Simberloff are particularly concerned about what they see as a siphoning off of conservation dollars for strips and parcels of high-priced urban and suburban land—money that might be better spent on acquiring intact blocks of healthy habitat in more remote locations. The science behind wildlife corridors and how plants and animals use them is still relatively new. The concept springs from the “island biogeography” work of two noted American scientists, Edward O. Wilson and Robert McArthur, in the late 1960s. Studying actual islands cut off from continents at the end of the last Ice Age, they observed that habitat isolation inevitably results in a loss of plant and animal species—with the greatest losses on the smallest and most isolated islands.

Twenty years later, ecologists began applying the concept to landlocked “islands,” arguing that the same kind of extinction patterns occur when hemmed-in wildlife populations can’t migrate or replenish themselves during times of disturbance such as drought or fire. Of particular concern: populations so small they suffer inbreeding without an infusion of migrants from surrounding habitat.

Driving home such concerns, a recent study of wildlife reserves in the eastern United States and Canada confirmed that conservation areas smaller than 1,000 square miles invariably lose species, mammals in particular. Worse, only 14 of the 2,355 refuges in the researchers’ study area met the 1,000-square-mile minimum threshold. The only hope of stemming the losses, they concluded in Conservation Biology, was to combine smaller reserves into assemblages with migration corridors.

“The idea that corridors are the solution to such problems is intuitively appealing and certainly intriguing,” comments University of Colorado ecologist Sharon Collinge. “But we need to be cautious about making sweeping generalizations about their importance.” To test how organisms use corridors, Collinge mowed a large field of mixed-grass prairie to create a collage of native grassland and bare patches. She then compared the success and failure of insect populations living in habitat patches with or without connecting corridors of vegetation. Collinge found that the corridors made little difference to the survival of insects in either very small or large patches of habitat. “Where patches were too small, the populations couldn’t persist regardless of corridors,” she explains.
“Where they were sufficiently large, the insects succeeded regardless of corridors.” Where Collinge saw an advantage was among populations in medium-size patches. Corridors might prove most important, she explains, when they connect habitats just large enough for a population to hang on, but small enough that individuals feel the pressure to migrate.

Collinge goes further to suggest that corridors might prove more important in situations where plants and animals face more daunting obstacles than mown prairie. “If the matrix around our habitat patches had been, say, a paved parking lot, we might have seen a much more dramatic effect,” she notes.

Clearly, the importance of corridors also varies depending on the plant and animal species involved, says ecologist Nick Haddad of North Carolina State University. Like Collinge, he began researching corridors using insects. Eight years ago, he created 27 four-acre clearings in a dense South Carolina pine plantation, connecting some of the new meadows with clear-cut corridors between 70 and 420 yards long. A year later, Haddad began monitoring the abundance of four native butterflies (cloudless sulphurs, common buckeyes, variegated fritillaries and spicebush swallowtails) in the clearings. Within a year and a half of the time the scientist created the corridors, populations of all but one species had become significantly larger in the connected versus isolated meadows.

Since then, Haddad and his colleagues have scaled up their experiments to look at a variety of small mammals as well as plants that depend on birds to disperse them. “Of the 15 species we’ve studied so far,” reports Haddad, “all but two move more frequently between connected than unconnected habitats.” The two exceptions thrive in a variety of habitats. “The message,” he adds, “seems to be that corridors prove especially important for habitat specialists—species restricted to a certain type of habitat.”
“Clearly, we are getting beyond the arguably simplis- tic question of whether corridors are good or bad,” says ecologist Paul Beier of Northern Arizona University. “The question may only make sense when talking about a particular species in a particular set of circumstances.” Beier’s own research has helped elevate this discussion. In 1998, he coauthored a landmark review of 32 previous corridor studies. The results cautioned against a blanket endorsement of corridors as a universal boon to wildlife. At the same time, the preponderance of studies supported corridors as one important tool in the conservationist’s arsenal. More importantly, perhaps, the review found no evidence that corridors have ever caused harm to a resident population, despite the hypothetical possibility that they could introduce predators and other threats.

Moreover, Beier’s overview helped expand the perception of corridors beyond that of mere highways for quick travel. Their greater importance, he explains, may lie in their use by organisms—from wildflowers to frogs—that would move across only over the course of many generations. In other words, an ideal corridor must provide the resources needed for an organism’s survival, not just its conveyance. “Plants don’t often move as individuals,” says Beier. “Some spread no farther than the adult plant’s seed shadow. Consequently, a corridor that allows plant migration would, in my mind, meet the highest standard.”

Florida’s Pinhook Swamp clearly falls into this category of corridor as habitat in its own right. However, there’s no avoiding the reality that such large tracts of habitat have become rare, especially in the populous eastern United States and the rapidly developing Southwest. The situation is somewhat better in the Northwest, where corridor advocates still have a chance of preserving large swaths of connectivity between even larger ecosystems.

Last year, the Interagency Grizzly Bear Committee—a group made up of staff from the U.S. Fish and Wildlife Service, Forest Service, Bureau of Land Management and state wildlife agencies—released a report that represents the most detailed long-term study ever undertaken of areas linking large blocks of public lands in the Northern Rockies. Although it deals primarily with grizzlies, the report essentially addresses the needs of other species that use the same corridors, such as lynx and wolverines. “We’re trying to find a consensus of where linkage zones are located in the Rockies so we can take steps to manage those areas effectively,” says Bill Ruediger, a member of the committee who also heads a new Forest Service program designed to find solutions to highway construction and other habitat-fragmentation in national forests.

Road construction became an issue not long ago in northwestern Montana, when the state Department of Transportation proposed widening a section of Highway 93 that passes through Salish-Kootenai tribal lands. Tribal members insisted that the plan include a variety of wildlife-crossing structures, from culverts for salamanders to overpasses for bears and elk. “The project is an excellent example of what highway engineers must consider and implement if we are going to avoid further fragmenting wildlife habitats into smaller, isolated patches,” says Tom France, director of NWF’s Northern Rockies Project Office in Montana.

In more heavily populated parts of the country, conservationists argue that it is not enough for developers to offer narrow set-asides of open space to mitigate their habitat destruction. “A coyote might use a dirt canyon to get through a suburban subdivision, but a bobcat probably won’t. And something as small as a six-inch step can prove insurmountable to a salamander,” says M.A. Sanjayan, a lead scientist for The Nature Conservancy who coordinated the California wildlife-corridor inventory with the California Wilderness Coalition. Recognizing such limitations, Sanjayan insisted that the corridor project place top priority on identifying large areas of healthy habitat where animal movement had been documented with scientific methods.

At the same time, Sanjayan argues, there’s no escaping the need to create what he calls “corridors of the last resort”—highway underpasses, riverbank buffers and other vegetation strips that might safely channel some animals through urban areas.
Meanwhile, proponents and critics of wildlife corridors can agree on the need to move quickly to preserve those intact tracts of wilderness still large enough to afford not only movement but long-term survival of resident wildlife. “If we don’t secure these lands now, they’re not going to be here 50 or 100 years from now,” warns David Dorman. “Now’s our chance.”

“If we don’t secure these lands now, they’re not going to be here 50 or 100 years from now.”

New York City journalist Jessica Snyder Sachs wrote about Georgia’s Chattahoochee River in the June/July 2001 issue.

Discoveries in Animal Behavior

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Copyright Jessica Snyder Sachs
(first published in National Wildlife magazine)

JAMES HARE stands in a grassy Midwestern pasture, tossing a tan fedora over the head of a female gopher (a.k.a. Richardson’s ground squirrel) as she emerges from her burrow. Hare, a zoologist with the University of Manitoba, knows that the swooping hat will trigger the gopher’s instinctive alarm response. She flicks her tail, opens her mouth and heaves her chest as if to give the sharp chirrup that announces “Hawk!” to the surrounding colony. Instead, she appears struck dumb, nothing but a faint whisper of air rushing from her gaping mouth.

The first time Hare observed this behavior several years ago, he came away puzzled. His fascination grew as he noticed other gophers opening their mouths as if to bark a warning, only to exhale with a barely audible call. An outbreak of ground squirrel laryngitis, perhaps? Hare’s early, lost-voice theory crumbled when closer study revealed gophers switching back and forth between their usual alarm calls and the strange, open-mouthed whisper.

Like Hare, scholars as far back as the ancient Egyptians and Greeks have puzzled over mysteries like these. Today the study of animal behavior, or ethology, is still one of biology’s most productive fields, with scientific journals brimming with reports on everything from the selection of gender-specific parental roles in cichlid fish to the importance of courtship song in fruit flies (seriously).

While much of this scholarly minutiae holds little draw beyond specialist circles, every year scientists make discoveries that overturn widespread assumptions or reveal previously unknown animal abilities. Here are just few of the more recent noteworthy finds.

Determined to solve the mystery of the whispering gophers, Hare returned to his university, where he borrowed an ultrasonic “bat detector.” Such devices lower high-frequency sounds—such as a bat’s echolocation shrieks—into human range by slowing down their pitch. Back out on the prairie, he pointed the device at emerging gophers as they reacted with visible but noiseless alarm to his presence. Sure enough, these were screams—at frequencies around 48,000 hertz. By contrast, the limits of human hearing reach only half as high, around 20,000 hertz. Hare suspected that he had discovered a “silent” alarm call.

To test the idea, graduate student David Wilson recorded silent screams from over a dozen gophers. He and Hare then replayed the recordings for gophers miles away. The ultrasonic cries produced much the same reactions as did recordings of audible alarms, with one clear difference. The ultrasonic recordings triggered alarm only in gophers close to and directly in front of the speakers.

The researchers’ conclusion: While the gopher’s silent alarm does not travel as far or wide as does the species’ familiar warning bark, a gopher can direct it, with laser-beam accuracy, to a nearby pup or other close relative, all without endangering itself by drawing attention from a predator. “This sort of thing may be far more common than we realize,” says Hare, who speculates that we live in a world filled with wildlife chatter beyond our senses.

That view gets support from a discovery at the opposite end of the sound spectrum. In Papua New Guinea, biologists from the New York-based Wildlife Conservation Society have recorded scarcely audible rumblings coming from the direction of large, ostrichlike birds called cassowaries. “It’s hard to describe, but you more feel it than hear it,” says study leader Andrew Mack.
He and his students have documented cassowaries producing “boom” calls at infrasound frequencies at the lower limit of human hearing—around 20 hertz and, by far, the deepest bird calls ever recorded. Mack suspects the solitary birds use their infrasonic booms to locate mates in the dense underbrush of the rain forest, where the vibration can carry for at least a mile.

In the mid-1800s, scientists began to speculate that some migratory birds rely on an internal compass to guide their journeys along Earth’s magnetic fields. Since this idea was accepted in the 1970s, they’ve found evidence for similar compasses in a wide range of other animals, including crustaceans, insects, fish, amphibians and mammals.

More recently, zoologists have shown that, in some birds, this navigational sense goes beyond a mere compass by providing maplike information about position—akin to today’s global positioning systems. Since then, the race has been on to find similar abilities in animals outside the bird family.

Surprisingly, the first clear evidence has turned up in a lowly invertebrate: the spiny lobster, which migrates up to 120 miles across the Gulf of Mexico and Caribbean. To shed light on how the animals accomplish this feat on the bottom of the sea floor—without sunlight or other visual clues—University of North Carolina researchers began studying young lobsters in the coastal waters off the Florida Keys. After capturing the crustaceans, the scientists transported them (inside closed containers) along circuitous routes of about 20 miles to one of two test sites, one north and the other south of their home range. To ensure the animals could not use visual cues to orient themselves, the researchers placed rubber caps over the lobsters’ eyestalks. Despite this, the lobsters all began walking in the direction of home—be that north or south of their drop-off site.

To test whether the lobsters were using geomagnetic navigation, the researchers returned to the home site and used powerful magnets to simulate the geomagnetic field conditions that exist some 250 miles either north or south. Sure enough, the lobsters exposed to the northerly magnetic field immediately began walking south, just as those exposed to the southerly field turned to walk north.

Sarah Brosnan had long marveled at the apparent generosity of the capuchin monkeys she studies at Yerkes National Primate Research Institute in Atlanta, where the animals live in two large and highly social colonies. If Brosnan left a bowl of food within reach of one capuchin but not another—separating them with a mesh partition—the first invariably shared by passing food through the divider.

As an anthropologist, Brosnan has a special interest in the roots of such behavior, specifically in mechanisms that encourage humans to cooperate when they receive no immediate benefit. Is the Golden Rule something we learn, or might it stem from an instinctual sense of fair play that we share with other primates?

At Yerkes, Brosnan designed an experiment to explore the question. First, she taught the monkeys a bartering game: She would hand one of them a small stone, then offer it a grape or a cucumber slice in trade. The capuchins eagerly bartered for either treat, though they clearly preferred the sweeter fare.

Next, Brosnan began giving one capuchin a grape, offering its partner a cucumber. The monkeys’ reaction to such unequal treatment could only be described as outrage, says Brosnan. “They’d literally throw their cucumber slices at me, something I’d never seen in all the years I worked with them.” The capuchins reacted even more negatively if they witnessed another receive the preferred treat for less work—if Brosnan handed their partner a grape, for example, without receiving a token exchange. In that situation, those offered cucumbers often threw away their stones or turned their backs on the scientist.

“People often turn down a reward because it’s not what they think is fair,” notes Brosnan. “Such self-defeating behavior may not seem rational, but our research suggests it traces to the kind of emotional sense of fairness that may promote the high level of cooperation needed in species that hunt or otherwise work closely together.”

Elsewhere in the primate world, researchers have documented another eerie mirror of human behavior: Girl chimpanzees appear to study harder than do their rambunctious brothers. Working in Tanzania’s Gombe National Park, University of Minnesota scientists tracked how young chimps learn to fish for termites using tools they make from sticks and stems. While both sons and daughters accompanied their mothers on termite-fishing expeditions, the daughters spent far more time watching and imitating, while the more-easily-distracted sons spent most of the time wrestling with each other.

As a result, most young females had perfected the skill by 30 months of age, while their brothers didn’t catch on until they were nearly twice as old. That’s not to say the boys were wasting their time, says study leader Elizabeth Lonsdorf. Their rough-and-tumble play may be important to sorting out dominance—a key factor in a male’s later reproductive success.

Behavior Benders: Pollutants Tied to Behavioral Oddities
In the 1970s, ornithologists began noticing a dramatic increase in same-sex California gull couples, with an abundance of female pairs attending nests brimming with both birds’ eggs. While most of the gay gulls did just fine raising their chicks, thank you, the abrupt change in behavior proved an early warning of something amiss. In the following years, the gulls began to show signs of acute poisoning by the pesticide DDT.

Fast-forward to 2004, and a flood of reports from field biologists documenting a veritable freak show of bizarre animal behaviors, from fearless mice, stupid frogs and paranoid ducks to spastic egrets, hyperactive doves and sluggish salmon. Add to these an especially disturbing increase in clueless mating behaviors and neglectful parenting in species from crustaceans to kestrels.

In these and scores of other cases, biologists have now traced the eccentricities to low-level environmental contamination with behavior-bending chemicals known as endocrine disrupters. “We’ve documented that hundreds of man-made pollutants have profound effects on animal behavior,” reports Amherst University biologist Ethan Clotfelter.

These chemicals include hundreds of biologically active pesticides, heavy metals and pharmaceutical products spread by runoff and seepage from farms, factories and municipal sewer systems. Worse, the low-level contamination has now pervaded every known ecosystem, from the tropics to the Arctic Circle. But with environmental testing geared to monitor for acute toxicity—that is, animals falling down dead—these behavioral disruptions have gone largely unnoticed, says Clotfelter, whose report on scores of such behavioral effects appeared in a recent issue of the journal Animal Behavior.

Clotfelter and other researchers who study endocrine disrupters are urging field biologists and laboratory toxicologists to recognize even subtle changes in animal behavior as a red flag that a particular chemical or an environmental cocktail of contaminants is approaching deadly levels.

“Like the DDT-poisoned gulls in the 1970s, you may see behavioral effects long before you see a population crash,” he says. And the weird behaviors alone may threaten the survival of species already on the brink of extinction. Examples include the loss of predator-evasion instincts in endangered Pacific salmon in streams contaminated with trace levels of pesticides from bordering farm fields.

New Jersey journalist Jessica Snyder Sachs wrote about the natural history of water in the June/July 2004 issue. To read about more animal behavior discoveries, see this month’s “Web Exclusives” at

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