Researchers examine this sea otter for clues to what might have killed it. Sea otters and other marine mammals sometimes fall ill from germs washed downstream and into the ocean. Credit: Calif. Dept. of Fish and Wildlife

Normally, doctors worry about how human illness will spread between people. But wildlife, too, can sometimes become infected with germs shed by people or their pets. And sometimes those germs may hit wild animals as hard — or harder — than they do people.

This is something that Melissa Miller has been studying for the California Department of Fish and Wildlife in Santa Cruz. As a veterinary pathologist, Miller studies animals to determine their cause of illness or death. She and her coworkers think of microbes as biological pollutants, which can harm animals in the wild. Human or animal feces — poop — are usually the source of these household germs that can wash into rivers and the ocean.

Natural wetlands can help slow the flow of polluted water. This gives beneficial bacteria in stream water the time they need to break down pollutants. But many communities have been converting wetlands to farms and residential areas. Now pipes and culverts move water quickly through what used to be slowly draining wetlands. The result, says Miller: Germs that typically live in land animals and people are sickening ocean mammals. These include sea otters, sea lions, dolphins and whales.

In the past few years, Miller and other researchers have discovered dead sea otters infected with a microbe called Toxoplasma gondii. This germ can cause nerve damage (including blindness) and retardation in people. It can cause deadly brain damage in otters. Miller and her coworkers now regularly examine the brains of dead California sea otters for signs of this infection, such as swelling and scarring.

Feces of infected land animals — typically wild and domestic cats — can spread the microbe. Feces and the germs they harbor get washed downstream and into the ocean. Clams, mussels, crabs and other filter-feeding animals can then ingest the germs. Animals that eat filter feeders can pick up the germ. “We think that is a big method by which sea otters are getting exposed,” explains Miller.

Sea otters can tell us a lot about the health of the environment, she says. One reason: These animals eat a quarter of their weight in food every day. Miller says that’s like a 160 pound person eating 40 pounds of hamburgers every day. Their large appetites and their living close to shorelines make sea otters particularly vulnerable to pollutants washed off of land. “What the otters are trying to teach us is that as much as we think [pollution] is going to go away, it actually just gets sent downstream and comes back to haunt us,” says Miller.

To help reduce sickness in wildlife — such as sea otters — keep pet cats indoors. In addition, seal pet wastes from litter boxes into bags before putting them in the trash. Towns near coastlines should also focus on preserving some natural areas as habitat for wildlife — and as a way to boost the breakdown of pollutants.

The student, Ngoc Mai Nguyen, says she told her boss, biologist Tyrone Hayes, “‘I don’t know what’s going on, but I don’t think this is normal.’” Nguyen, a student at the University of California, Berkeley, was working in Hayes’ laboratory. Hayes told Nguyen to keep watching — and write down what she saw each day.

Nguyen knew all the frogs had started out as males. She didn’t know, however, what Hayes knew: that there was something in the water of the frog tank. That something was a popular weed killer called atrazine, and since birth the frogs had been raised in water that contained the chemical.

Hayes says the experiments in his lab show that 30 percent of the male frogs that grew up in water with atrazine started to behave like females, and even send out chemical signals to attract other males.

When this frog species is raised in the lab in water tainted with what EPA considers acceptable concentrations of atrazine, males change — sometimes into apparent females.

Furryscaly/Flickr

Laboratory experiments are not the only places where frogs may run into atrazine. The chemical is used as a weed killer, so it can pollute surface water downstream of the crops where it is used. In these rivers and streams, the concentration of atrazine can reach 2.5 parts per billion — the same concentration Hayes tested in his laboratory. This similarity suggests that male frogs may be turning into females in their natural habitats.

The Environmental Protection Agency, or EPA, is a government organization responsible for protecting human health and the environment. The EPA defines what concentrations of certain chemicals are allowed in U.S. waterways, and the EPA has determined that up to 3 parts per billion — well above the concentration that turns male frogs into females — of atrazine is safe. If Hayes is right, even the EPA definition of a safe concentration is actually not safe for frogs.

Hayes and his team have also showed that it’s not just the frogs’ behavior that changes after exposure to atrazine. Males raised in water containing atrazine had low levels of testosterone and did not try to attract females.

But that’s not all: Out of 40 frogs raised in water containing atrazine, four had high levels of estrogen — a female hormone (that’s four out of 40 frogs, or one in 10). Hayes and his team dissected two of the frogs and found female reproductive organs. The other two transgender frogs were introduced to healthy males and mated with those males, producing baby male frogs.

Other scientists have looked at Hayes’ work and carried out similar experiments — with similar results. Plus, researchers who study other animals have observed that atrazine affects those animals’ hormones.

At least one scientist, Tim Pastoor, says Hayes has made mistakes in his study and that atrazine is safe. Pastoor is a scientist with Syngenta Crop Protection, a company that makes and sells atrazine.

In an email to Science News, Pastoor wrote that Hayes’ new experiments don’t lead to the same results as Hayes’ earlier studies. “Either his current study discredits his previous work, or his previous work discredits this study,” Pastoor wrote.

It’s important to know how atrazine affects the animal population. Any chemical that can change the reproductive patterns of an animal threatens that species’ survival.

It doesn’t take long before a hive is nearly empty. Researchers call this phenomenon colony-collapse disorder. According to surveys of beekeepers across the country, 25 to 40 percent of the honeybees in the United States have vanished from their hives since last fall. So far, no one can explain why.

Inspecting a honeycomb from a healthy hive (above), beekeeper Dan Geer finds bees densely packed. A honeycomb from a hive whose colony is collapsing (below) has far fewer bees.

Cutraro (both images)

Colony collapse is a serious concern because bees play an important role in the production of about one-third of the foods we eat, including apples, watermelons, and almonds. As they feed, honeybees spread pollen from flower to flower. Without this process, called pollination, a plant can’t produce seeds or fruits.

Now, a group of scientists and beekeepers has teamed up to try to figure out what’s causing the alarming collapse of so many colonies. By sharing their expertise in honeybee behavior, health, and nutrition, team members hope to find out what’s contributing to the decline and to prevent bee disappearances in the future.

Sick bees?

It could be that disease is causing the disappearance of the bees. To explore that possibility, Jay Evans, a research entomologist at the United States Department of Agriculture (USDA) Bee Research Laboratory, examines bees taken from colonies that are collapsing. “We know what a healthy bee should look like on the inside, and we can look for physical signs of disease,” he says.

And bees from collapsing colonies don’t look very healthy. “Their stomachs are worn down, compared to the stomachs of healthy bees,” Evans says. It may be that a parasite is damaging the bees’ digestive organs. The bees’ inability to ward off such parasites suggests that their immune systems may not be working as they should.

The honeybees have other signs of troubled immune systems, such as high levels of bacteria and fungi inside their bodies, says Dewey Caron, an entomologist at the University of Delaware. He’s one of the leaders of the colony-collapse research team.

But why would parasites, bacteria, or fungi in the body cause bees to leave their hives? After all, when you’re sick, you want to stay at home, right?

Caron says that some of these disease-causing agents may lead to disturbances in bee behavior. “It may be that sick bees are not processing information correctly and learning where home is,” he says. In other words, a sick bee might leave the hive and simply forget how to get back.

If enough of the bees in a colony can’t find their way home, he says, it’s just a matter of time before the colony collapses. Being social insects, even healthy bees are unable to live long on their own. And once the bees vanish, the crops that they usually pollinate are in trouble.

Environmental clues

Another cause of colony-collapse disorder may be certain chemicals that farmers apply to kill unwanted insects on crops, says Jerry Hayes, chief bee inspector for the Florida Department of Agriculture. Some studies, he says, suggest that a certain type of insecticide affects the honeybee’s nervous system (which includes the brain) and memory. “It seems like honeybees are going out and getting confused about where to go and what to do,” he says.

Adding to the mystery, Hayes says, is an observation about moths and other insects that frequently use empty beehives to raise their own young.

“Usually, they move right into an empty hive,” he says, “but now they’re waiting several weeks before they do.” As Hayes sees it, this suggests that something repellent in the hive may not only be driving out bees but also keeping other insects from moving in, he says. So far, scientists haven’t identified what that repellent thing could be.

Looking at bee genes

If it turns out that a disease is contributing to colony collapse, bees’ genes could explain why some colonies have collapsed and others have not. In any group of bees—or other animals, including people—there are many different kinds of genes, because each individual has a slightly different unique set of genes. The more different genes a group has, the higher the group’s genetic diversity. And genetic diversity is a plus as far as survival is concerned.

Some scientists are now studying genetic diversity in honeybee colonies to see if it has an effect on colony collapse disorder.

“If a colony is genetically diverse, it’s less likely the colony will be wiped out completely from a sweeping infection or disease,” says David Tarpy, a University of North Carolina entomologist. That’s because at least some bees in a genetically diverse group are likely to have genes that help them resist any specific disease that gets into the colony, he says. Scientists haven’t determined the role of genetic diversity in colony collapse, but it’s a promising theory, says Evans. He and his colleagues at the USDA bee lab are currently running genetic tests on bees from collapsing colonies. Their goal is to find out whether there are genetic differences between the bees that vanish and those that remain in their hives.

Beekeeping helps support these important, pollinating insects.

Cutraro

Scientists are working hard to figure out the causes of colony collapse. Meanwhile, bees continue to disappear. Can anything be done to help them survive?

Tarpy suggests that more people could raise bees to help restore their numbers. “Given this decline in honeybees, if you want to get active in helping to promote pollination, the best thing to do is to become a beekeeper and keep your own bees,” he says.

Don’t be put off by the possibility of a sting, says Dan Geer, who raises bees in North Smithfield, Rhode Island. First of all, beekeepers can wear protective gear. And bees, he says, have a bad rep. “You’d be surprised by how gentle they are,” he says.

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