PESTS OF ALL SIZES
Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond.
Greetings everyone and welcome to the last column of the year. I thought today we’d take a little trip through the animal file and see what we can find about the critters that share our world with us.
One critter I can definitely do without is the mosquito. Besides the fact that the mosquito is annoying and painful, it’s also a notorious spreader of disease. Quite frankly, I personally think we’d be better off without them. Here’s a sad little tale of economics and pests.
TAKING OUT THE STING
After searching for more than 50 years, scientists finally have discovered a number of new mosquito repellents that beat DEET, the gold standard for warding off the pesky insects. They sound like a dream come true. They repel mosquitoes for up to three times longer than DEET, the active ingredient in many of today’s insect repellents. They don’t have the unpleasant odor of DEET. And they don’t cause DEET’s sticky-skin sensation. But there’s a mosquito in the ointment: The odds appear to be stacked against any of the new repellents ever finding a place on store shelves.
Ulrich Bernier, Ph.D., the lead researcher for the repellent study, said that costly, time-consuming pre-market testing and approval is a hurdle that will delay the availability of the repellents, which were discovered last year.
Making the repellents commercially available takes significant investment in both money and time. The cost may be several hundred thousand dollars. Once it’s determined that the repellent works then there’s also a toxicological hazard evaluation involving numerous toxicological tests."
If the repellents continue to work well when tested in the laboratory on human skin, and if they pass the battery of toxicological tests, they still face a series of tests to prove their effectiveness against mosquitoes.
Bernier and his team discovered the repellents with what they say is the first successful application of a computer model using the molecular structures of more than 30,000 chemical compounds tested as repellents over the last 60 years. Using 11 known compounds, they synthesized 23 new ones. Of those, 10 gave about 40 days protection, compared to 17.5 days for DEET, when a soaked cloth was worn by a human volunteer. When applied to the skin, however, DEET lasts about five hours.
Bernier routinely participates in repellency studies, which involve about 500 mosquitoes trying to land on his arm and bite through a repellent-soaked cloth. If the mosquitoes don’t land, the researchers know the repellent is working. If they walk around on the cloth-covered-arm, they’re on the verge of being repelled. If they bite…then it’s on to the next repellent.
To search for the best repellents, the team devised software that recognized structural features of a chemical that would make it effective in keeping the bugs away. They trained it by feeding it the molecular structures of 150 known repellents. Based on this information, the program learned to identify the chemical traits of a good repellent without the chemists even having to know what those traits were. For example, the team checked out 2,000 variants of a compound found in black pepper that repels insects.
I hope that they get some funding to market these new repellants soon. I’d sure buy them!
Mosquitoes stay away from repellent-soaked cloth on the arm of researcher Ulrich Bernier. (Credit: Greg Allen, U.S. Department of Agriculture, Agricultural Research Service)
And now we move on to a tale of another of the least-loved animals on the planet.
YOU THINK WE’VE GOT PROBLEMS??
I’m having a little mini-invasion at my house. I’m surrounded by forest and a large family of brown tree snakes seems to have decided to call my house and my dog food theirs. We whip them around a mop handle and dump them in the freezer. No more blood, no more machete nicks on my stuff. It’s a humane way to die, not that I really care because brown tree snakes are aggressive and I’ve been bitten several times.
Brown tree snakes can get quite large, but they don’t hold a candle to the subjects of this story. The southern United States is being invaded by some of the biggest snakes on the planet.
A new report by the U.S. Geological Survey (USGS) tells all about the risks of nine non-native snake species including boa constrictors, anacondas and pythons. Two of the species have been documented as reproducing in the wild in South Florida where the Burmese python population is already reported to be in the tens of thousands.
Although the giant snakes don’t pose a great threat to humans, adults of the largest pythons have been known to attack and kill people in their native habitats. The snake most often associated with attacks on humans is the reticulated python, a native of Southeast Asia.
Although many of the giant snakes snake species may be confined to the deep South, others like Burmese pythons, northern and southern African pythons, boa constrictors and yellow anacondas put larger portions of the U.S. mainland at risk.
The USGS scientists who authored the report point out that native U.S. birds, mammals, and reptiles have never had to deal with huge predatory snakes before. Individuals of the largest three species reach lengths of more than 20 feet and upwards of 200 pounds. The reticulated python is the world’s longest snake, and the green anaconda is the heaviest snake. Both species have been found in the wild in South Florida, although breeding populations are not yet confirmed for either.
Breeding populations have been confirmed in South Florida for Burmese pythons and the boa constrictor, and there is strong evidence that the northern African python may have a breeding population in the wild as well.
Unfortunately these snakes mature early, produce large numbers of offspring, travel long distances, and have broad diets that allow them to eat most native birds and mammals. In addition, most of these snakes can inhabit a variety of habitats and are quite tolerant of urban or suburban areas. Boa constrictors and northern African pythons, for example, already live wild in the Miami metropolitan area.
The report notes that there are no controls adequate for eradicating an established population of giant snakes once they have spread over a large area. Making the task of eradication more difficult is that in the wild these snakes are extremely difficult to find since their camouflaged coloration enables them to blend in well with their surroundings.
Dr. Gordon Rodda, a herpetologist who lived on Guam, mentions us in the report. “We have a cautionary tale with the American island of Guam and the brown tree snake,” he says. “Within 40 years of its arrival, this invasive snake has decimated the island’s native wildlife: 10 of Guam’s 12 native forest birds, one of its two bat species, and about half of its native lizards are gone. The python introduction to Florida is so recent that the tally of ecological damage cannot yet be made.”
USGS researchers used the best available science to predict areas of the country most at risk of invasion by these giant snakes. Based on climate alone, many of the species would be limited to the warmest areas of the United States, including parts of Florida, extreme south Texas, Hawai
i, and America’s tropical islands, such as Puerto Rico, Guam, and other Pacific islands. For a few species, however, larger areas of the continental United States appear to exhibit suitable climatic conditions. For example, much of the southern U.S. climatic conditions are similar to those experienced by the Burmese python in its native range.
The Fish and Wildlife Service and the National Park Service will use the report to help them figure out what to do about the problem and how to prevent further colonization.
Researchers implant a radio transmitter in a 16-foot, 155-pound female Burmese python at the South Florida Research Center, Everglades National Park. Radio-tracking builds understanding of where pythons spend their time and therefore where they can be controlled in practice. Photo courtesy of Lori Oberhofer, National Park Service. (Credit: U.S. Geological Survey)
I once had a very good friend in Pete, the reticulated python. Despite her name, she was a female and she was a mascot for one of the units at U-tapao Air Base in Thailand. She had been captured on the flightline about five years before I got there and at that time, she was three feet long and weighed 30 pounds.
To keep Pete fed, the Thais who ran the café where she was housed ran a lottery. They put a chicken in the cage with Pete once a week and for a quarter, you could put in your guess of the day and time that Pete ate the chicken. The person who came the closest got the money, less the amount to buy the next week’s chicken.
Reticulated pythons don’t eat that often in the wild and when I left Thailand, Pete was 33 feet long and weighed 300 pounds. Most times, when I came to call, she would rear up her head until it was on the level of mine and we would chat. I never decided if she was just curious about the white lady, or viewed me as lunch. She was an impressive animal, but not one I’d want to meet in my back yard!
