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
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.
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.
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.
links to this scientist's home page and other related infomation
please see our resources
I just wanted to ask how does the virus that you developed
work in the bodies of the snakes to kill them? Thank you
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.
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?
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.
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.
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
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
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.
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.
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".
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.
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.
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
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
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."
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.
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.
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.
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.
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.
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
Is there any way to reduce the threat of non-native species
without killing the entire population?
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.
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.