The effects of the Brown Tree snake on Guam

The effects of the Brown Tree snake on Guam

Boiga irregularis also known as the brown tree snake as a common name is a member of the Colubridae family that comprises of snakes that were known to be harmless initially. The brown tree snake originates from Coastal Australia and other islands found in north-western Melanesia. Though it is known as the brown tree snake, its main habitat is not in highly forested areas. It occurs in sparsely forested places as well as in grasslands. The snake is commonly found in caves, trees, hollow logs where it hides during the day and comes down at night to forage.

The original length of the brown tree snake is three to six feet long, but this snake has achieved lengths of up to ten feet in areas where food supplies are in plenty. The snake is also slim in addition to it being very long giving it the ability to climb faster and pass through small spaces. The snake varies in colour ranging from yellow, green and brown with different patterns. These colours allow the snake to camouflage well to better capture its prey. The brown tree snake is an effective colonizer because it can feed on a variety of foods. These snakes feed on lizards, frogs, small mammals, bird’s eggs and birds (Finley & Finley Jr., 2005).

The reproductive system of brown tree snake is complicated and little is known about it. The female lays eggs in cave or a hollow log where they protected from dehydration. The female is able to lay eggs twice a year, but it depends on availability prey and variation in climate. Just like most snakes the female brown tree snake has the ability to store sperms for a long time after mating where fertilization occurs after the female produces the eggs.

The brown tree snake is very aggressive when attacked or threatened. They have grooved teeth that inject venom and they are likely to bite several times. The venom is poisonous and effectively kills the prey after which the snake wraps its body around the prey to immobilize it while feeding on it. The venom is however not considered harmful to adult humans but has been known to cause respiratory complications.

Invasion of the Brown Tree Snake in Guam

Just like the serpent in the Garden of Eden that brought a lot of destruction, the brown tree snake caused the extinction of birds in Guam. According to Eldredge (2002), within the last fifteen years, the twelve native species of birds in Guam have been reduced to three with extinction of nine native species and subspecies. This is due to the introduction of the snake following the end of the Second World War. As the bird’s species became extinct, the scientists in Guam did not know the predator that was responsible and this enabled the brown tree snake to expand across the island of Guam. The brown tree snake was first reported to be in Guan in 1950s. Rodents were the common prey for the snake and therefore, it was not termed as a threat to birds.

Eldredge (2002) attributes the expansion of the brown tree snake population to ample food supply and lack of predators. The population growth was exponential and they colonized most of the kingdom feeding on rats, lizard, juvenile bats incapable of flight and birds (Finley & Finley Jr., 2005). Bird’s species were declining at a high rate and so was the other animals that were being preyed on by the snakes. Birds disappeared at a high rate because the brown tree snake dwells on trees and preys on bird’s eggs, nestlings and adult birds. The only species of birds that have not suffered great reduction in number or extinction are those that inhabit treeless areas (Eldredge, 2002). In 1984, the United States Fish and Wildlife declared that most native birds in the forest habitant in Guam were termed as extinct or endangered.

The extinction of most of the native species of birds in Guam was a tragic loss for biodiversity compounded by secondary effects that the people of Guam are beginning to understand (Eldredge, 2002). The decline of bird’s species that preyed on insects has led to the increase in population of insects resulting in the destruction of crops. Bats which are also prey to the brown tree snake play a crucial role in seed dispersal as well as pollination. The plant population has been greatly affected by the drastic reduction of birds and bats. Unfortunately, the extinction of most of the bird’s species came at a time when little was known about the species and their ecological importance. According to Simberloff and Rejmanek (2011) the brown tree snake has also directly affected humans because it also preys on domestic birds and has been known to attack children in their sleep. The snakes are also notorious for causing electrical outages. Power interruptions are costly to humans and also cause inconveniences. Venomous bites by these snakes are not fatal to humans, but have been known to cause respiratory complications. Guam has also lost a lot of revenue because tourist are not comfortable frequenting the area due to the fear that the snakes have instil in most people and the publicity of their presence in Guam.

The fate that has befallen Guam and the extensive damage caused has arisen an alarm in neighbouring countries where they are afraid of invasions by the brown tree snake. Unfortunately, the conditions that led to the invasion of the brown tree snake in Guam still prevail. The snake was transported unintentionally to Guam by the military during transportation after the Second World War. The same could happen where the snakes are likely to be transported to various locations.

Control of Brown Tree Snakes on and off Guam

According to Simberloff and Rejmanek (2011) the risk of further invasion is what has prompted policymakers to fund the efforts to eradicate the brown tree snake from Guam. This is done through inspection of all networks of transportation to ensure that these snakes are not transported from one place to another. The other method is to biologically control the population of the brown tree snakes by understanding the snakes biologically. The greatest advantage is that Guam is geographically isolated and he only means through which the snakes can leave the island is by a sea vessel or an aircraft. Traps have also been place around airports to ensure that the snakes do not get in. The airport staff have also been trained on how to identify the hiding areas for these snakes and the safest way to capture them.

Although operations to eliminate the brown tree snakes from Guam is efficient mainly due to the research carried out as well as the lessons that the people of Guam have learned, the system is not perfect and the snakes have been found in other locations especially those where transportation is done frequently. Places like Hawaii are susceptible to invasion, but they have laid down policies that are likely to offer them protection in case of invasion. Eradication of these snakes in other places is likely to be more effective than Guam, because they are more prepared.

As discussed by Eldredge (2002) researchers are looking into ways of poisoning the brown tree snake or introducing a disease that would cause the death of the snakes, but this might pose a threat to other species as well as other animals they come into contact with. Other methods include placing electric barriers on trees as well as trimming of branches to prevent the snakes from hiding. The methods are however not very effective because they are expensive, labour intensive and impossible to cover a large area.

Conclusion

The brown tree snake has cause major destructions in Guam after its invasion. The snakes grew in numbers further causing destruction in Guam due to the presence of food and lack of prey. Though Guam in conjunction with other neighbouring countries have tried to eliminate the snakes, their efforts have not been very successful and the snake have been spotted in other locations. For elimination of these snakes to be possible, Guan will be required to spend a lot of money on research. Biological elimination of these snakes is more effective than use of electrical guards and the trimming of trees. The scientist could identify predators of the brown tree snake, increase them in number and strategically put them in the same habitat. They should be careful to ensure that the predators do not prey on other species of snakes because this would cause further destruction to the ecosystem. Complete elimination of the brown tree snake from Guam is possible, but it could take a lot of time for this to be realized.

References

Eldredge, N. (2002). Life on Earth: An Encyclopaedia of Biodiversity, Ecology and Evolution. California: ABC-CLIO.

Simberloff, D. & Rejmanek, M. (2011). Encyclopaedia of Biological Invasions. California: University of California Press.

Finley, R. & Finley, R. Jr. (2005). Intermittent Frontiers: On How Changing Ecological Factors Control Natural Selection. USA: Pilgrims Process, Inc.