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Photo of Nichols Don Nichols
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Donald Nichols has worked as Associate Pathologist at the National Zoological Park in Washington, DC since 1991. He previously served as Senior Staff Pathologist in the United States Public Health Service, part of National Institutes of Health.

In his current role, Nichols works to keep the animals at the zoo healthy by studying the ailments that occasionally afflict them. This work has relevance in the wild, too. Nichols applied his expertise to finding out why frog populations have plummeted worldwide.

Nichols obtained his BA in Mathematics at the University of Virginia before completing his degree in veterinary medicine in 1984. In 1988, he became a Diplomate of the American College of Veterinary Pathologists.

A prolific author of peer-reviewed papers, Nichols also served as Associate Editor for the Journal of Zoo and Wildlife Medicine from 1996 - 2000. He has led workshops at the Annual Meeting of the American Association of Zoo Veterinarians, and belongs to numerous professional and honorary societies.

     

For links to this scientist's home page and other related infomation please see our resources page

Nichols responds :

11/8/01 Rafeek asks:
I just wanted to ask how does the virus that you developed work in the bodies of the snakes to kill them? Thank you

Nichols' response:
The viruses on which I am concentrating my research are known as ophidian paramyxoviruses. They affect the respiratory tract of the snake, primarily the trachea and lung (brown tree snakes, like most snakes, only have one lung). In the lung, the viruses cause proliferative pneumonia (inflammation and thickening of the thin membranous tissues), and this interferes with oxygen absorption.

11/7/01 Navneet asks:
How come the snake population is growing so much faster in Guam? Why do they want the people to eat snakes? Would it affect their health?

Nichols' response:
The brown tree snake is not native to Guam; its native range is Australia, New Guinea, and the Solomon Islands. This snake was accidentally introduced onto Guam sometime after World War II. Because Guam did not have any native snake species prior to this, there were no snake predators or diseases present to keep the brown tree snake population in check. This has allowed the snakes to reach population densities on Guam that are unprecedented for any snake species anywhere else.

The idea behind trying to get people to eat the snakes was that if people thought they tasted good, the snakes would be "harvested" for food on a large scale and this would reduce the island-wide population. The biggest problem with this is that the snakes are very slender, which is advantageous for life in trees. Thus, there is relatively little meat to eat (and lots of rib bones to deal with), even on the very large individuals. It is very time-consuming to catch, prepare, and cook the snakes for such a little amount of food obtained. These snakes have not become popular food items.

Reptiles can carry Salmonella and other bacteria that can make people sick. When preparing any reptile for consumption, people must be very careful not to contaminate the meat with intestinal contents. The food must also be thoroughly cooked. If the snake meat is properly prepared and cooked, there should not be any health concerns about eating it.

11/7/01 Armine asks:
I wanted to know or suggest to you if you can catch the snakes and make them infertile instead of killing them, because I think that it's very cruel to inject them with a virus. Please consider my opinion because we don't need to add the brown tree snakes to the long list of extinct animals.

Nichols' response:
Brown tree snakes are not native to Guam. They have already caused the extinction of 9 bird species and at least 3 lizard species on Guam. The remaining birds, lizards, and fruit bats are facing extinction due to predation by these snakes.

There is no advantage in making the snakes infertile, since infertile snakes will continue to eat Guam's native species. Also, because the snakes have to be caught to be made infertile, then it makes more sense to kill them right away. But catching the snakes is labor intensive, expensive, and cannot be practically done on a wide scale. Therefore, a better method of reducing the snake population is clearly needed.

I would also like to point out that in order to make these snakes infertile, one would need to perform a painful surgical procedure on them, which many people would consider to be "cruel".

Using biological control agents such as the viruses that I am working with, one can infect a snake and let it go so it will infect other snakes. Thus the control method becomes amplified in the snake population.

Brown tree snakes are plentiful and in balance within the ecosystems in their native range. They are not endanger of extinction. I am proposing that biologic control be used to significantly reduce the snake population on Guam, where they simply do not belong.

11/7/01 Paul asks:
Why not import some male mongooses (Herpestes edwardsi) from India who are natural predator to snakes. With an average life span of 20 years and no females to keep the population growing on the island you eradicate your snakes with out fear of the mongooses taking over the island. Basically you would be using nature to fight nature

Nichols' response:
Actually, the reputation that mongooses have for being predators of snakes is exaggerated. While it is true that a mongoose will eat a snake, it would much rather eat birds, lizards, and small mammals. It is far more likely that mongooses on Guam would eat more animals of Guamanian native species (and people's chickens) than brown tree snakes, especially since mongoose tend to be diurnal and do not climb trees well whereas the snakes are nocturnal and primarily arboreal.

The snake viruses on which I am conducting research were isolated from disease outbreaks in captive collections of snakes. These are naturally occurring viruses. I am NOT creating these viruses; I am simply determining what effects they have on brown snakes. Thus I am "using nature to fight nature."

11/6/01 Burt asks:
Dr. Nichols: I am curious about how you researched the existence of a reptilian virus which is strictly limited to a specific species. I am a DOD scientist, interested in finding and testing such a bug which is similar to mammalian viruses, and can be used in outdoor tests with extremely small chance of affecting the environment.

Nichols' response:
Let me start out by giving you more of my background. I am a veterinarian with a life-long interest in reptiles and amphibians. After veterinary school, I decided to specialize in pathology (the study of disease and disease processes) which required 4 more years of specialized training. My particular focus of attention for the past 19 years has been the diseases of "exotic" animals and wildlife, especially reptiles and amphibians. Over the years, I have seen several outbreaks of respiratory disease in snakes due to ophidian paramyxoviruses. From my experiences (and those reported by others), we know that these viruses are snake-specific.

After I became aware of the snake problem on Guam, it became clear to me that the only practical way that this population will ever be controlled is through the use of biological control. The biological control agent(s) to be used would need to be snake-specific, highly-contagious, and cause a high mortality rate. Since I knew that ophidian paramyxoviruses can have all of these characteristics, I chose to concentrate my studies on these viruses. The next step was to find one or more strains of the viruses that cause high mortality in brown tree snakes.

Of course, before we could ever release paramyxoviruses on Guam, we would need to prove that the native species on Guam are not affected. This will be done in a carefully controlled laboratory setting here on the mainland.

11/6/01 Kurt asks:
Have you or any other scientists used pheromone attractants to lure the male brown tree snakes into traps? Also, these snakes are considered to be a delicacy in Japan, why haven't they been marketed to them? Snake sushi...yum.yum.

Nichols' response:
A colleague of mine, Dr. Robert Mason, is a professor of zoology at Oregon State University and an expert on snake pheromones. Dr. Mason has been conducting research on brown tree snake pheromones for the exact purpose that you mentioned. He has identified some pheromones but more work needs to be done in this area. I have never heard that these snakes are eaten in Japan (or anywhere else other than occasionally on Guam). As I explained in my answer to Question 2, there is not much incentive to eat these snakes because they have relatively little meat.

11/8/01 EDOG asks:
Is there any way to reduce the threat of non-native species without killing the entire population?

Nichols' response:
The fewer snakes there are on Guam, the less of a threat they pose. Right now, it is estimated that there are 1-2 million brown tree snakes on Guam. It also appears that the population is fairly stable. Although these snakes have almost totally depleted the birds, bats, and several lizard species on Guam, the remaining lizards and rodents can apparently reproduce quickly enough to maintain the snake population at its current level.

The snake control program currently used on Guam is concentrated around the airports and seaports. This program is primarily designed to prevent the snakes from escaping Guam and being introduced elsewhere. This program is not having any significant impact on the island-wide snake population. Because this program is labor intensive and expensive to run, it could not be expanded to cover large areas of the island.

It is not realistic to expect a virus or any other biological control agent to kill 100% of the snakes (this is theoretically possible, but not likely). However, a 75% or more reduction in the snake population would greatly reduce the ecological and economic impacts that the snakes have on the island. Biological control could be used along with more conventional control methods to keep the snake population suppressed down to a "manageable" level. This would allow the native species to recover and reduce the chances of the snakes escaping to other islands.


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