More than a Pest, Invasive Animals Quiz

Answer: Brown tree snake

The brown tree snake is indigenous to Indonesia, the Solomon Islands, New Guinea, and Australia. It is believed that they were introduced accidentally to Guam by the U.S. military during World War II when men and equipment were moved between islands in the South Pacific.

The brown tree snakes have killed many animals and small mammals such as lizards, birds, eggs, and rats in Guam. Other side effects are damage to electrical lines and a reduction in tree seed germination due to the loss of birds and mammals that would normally perform that role.

It's estimated that the brown snake population is 13,000 snakes per square mile. One of the efforts to control their effect is building bird nests on poles with metal bands to hinder snake movement. Some reduction or control arises from traps and fences to exclude them from critical areas. Poison is used as a last resort due to possible side effects on other animals and plants.

Answer: Beaver

The Argentine Government introduced the North American beaver in 1946 to the southern area of Patagonia in an attempt to establish the fur trade.

Beavers lacked natural predators in the area, and the region, with its many rivers and trees, was an ideal environment for them. Coupled with the unwillingness or inability of local residents to hunt them, the beaver population grew at a rapid rate.

This has contributed to reductions in forested regions and changes in river flow due to the construction of beaver dams. It should also be noted that the Patagonia and Tierra del Fuego regions are pristine environments that have been affected very little by human presence; and that environment is being disturbed by the introduction of beavers.

Answer: Burmese python

There are two possible sources for the Burmese python infestation in Florida. One is that people disposed of them in the Everglades when the snakes grew too large to keep as pets. Another is an influx of the snakes occurred when Hurricane Andrew destroyed a building housing them and carried them into the Everglades.

Having no natural predators in the Everglades, they have spread throughout the area. Most of the mammal population has been eliminated throughout the swamp, giving free rein to rats. There have been reports of battles with the other apex predator, the Florida alligator.

Attempts to reduce the number of pythons have been relatively unsuccessful. Hunts and bounties for dead pythons have had some effect. Some captured male pythons have had tracking devices installed to help identify breeding females for capture and elimination. The best hope is a prolonged spell of very cold weather.

There is serious concern that the python may migrate north, especially with warming weather in the future.

Answer: Imported for pest control

The cane toad is a large toad native to Central America and the northern sections of South America. Its survival depends on prolific breeding (female laying 8000 to 25000 eggs at a time) and its toxic poison used against possible predators.

The toad can be used to control agricultural pests and was introduced, sometimes successfully, to many regions. Without natural predators and the ability to kill native species, it has spread rapidly.

An example of the damaging effects from importing cane toads occurred in Australia, when they were introduced in to control the native grey-backed cane beetle and French's beetle. Lacking natural predators, the cane toad population increased rapidly; and they had limited effect on the beetles affecting cane production.

The cane toad and its tadpoles are toxic to many other species. Some of the effects in Australia of this are the reduction of the number of dung beetles, birds, and snakes. The fewer number of goannas has been linked to an increase in the number of undamaged crocodile eggs and their population.

Answer: Released from ballast tanks and hulls of ships

The zebra mussel is a small freshwater mussel that originally came from Russia and the Ukraine. They are filter feeders and have reduced pollution and increased clarity in many lakes and rivers. The resulting increased sunlight has increased the growth of submerged plants and bottom-feeding fish.

However, the zebra mussel has caused very serious problems in North America as it spread from around 1988. They often successfully cover and eradicate other freshwater mussels. They collect densely in pipelines of water supplies and block the intakes of hydroelectric plants. They are thought to be the cause of some avian botulism, when the birds ingest pollutants from the mussels.

It's believed that they were introduced from the ballast or anchors of ships transversing the St Lawrence Seaway. Continued spread to other bodies of water has occurred due to mollusks present on shipping and pleasure boats.

Answer: Alewife

The alewife is the name given to a member of the shad family, which normally lives in the Atlantic and estuaries leading to it. The Welland Canal provided a clear path to the Great Lakes, where the alewives became abundant in Lake Huron and Lake Michigan.

For many years, the alewife population grew at a rapid rate due to the absence of a natural predator. The alewife dominated this region and reduced the numbers of native Great Lakes fishes and zooplankton. It also suffered periodic die-offs, which resulted in large numbers of them being washed ashore - an unpleasant occurrence for nearby residents.

Overfishing, the introduction of Pacific salmon as predators, and invasion of sea lampreys have done much to reduce the numbers of alewives from their peak between 1950 and 1980.

Answer: Hippopotamus

Pablo Escobar introduced four hippopotamuses to his private menagerie in the 1970s. When he died in 1993, the animals were too difficult to move and roamed his estate freely, growing to a herd of around 200 with a range of over 2000 square kilometers.

The hippos pose an ecological threat by eating large amounts of vegetation, changing the composition and oxygen content of the local Magdalena River due to their excrement, and displacing native animals. Although there have been only two attacks on humans near his former estate, hippopotamuses kill about 500 persons a year in Africa and could become a threat in Colombia.

Efforts to cull the herd have met strong opposition. Some progress has occurred with the use of contraceptives and sterilization, and there are plans to capture and shift part of the population to other countries.

Answer: Attempt to start a silk industry

Note: in 2022 the Entomological Society of America renamed the gypsy moth to the spongy moth as part of an effort to remove offensive names. "gypsy moth" is used here in some places due to the term being more familiar.

In 1869 Étienne Trouvelot imported the moths from Europe, with the intent of interbreeding them with silk moths to establish a new silkworm industry; but the moths were accidentally released from his residence. Within ten years, the moth was already considered a nuisance; and within twenty years major devastations had occurred.

The moth is considered one of the most serious invasive species to affect hardwood trees in North America, defoliating millions of acres of forests in the north-eastern states. It is listed as one of the 100 most destructive invasive species world-wide. The larvae are spread primarily by wind, and some eggs are also transported through firewood cuttings.

Small mammals, such as the white-footed mouse and the short-tailed shrew, feed upon the larvae and pupae lying close to the ground; and extended periods of cold, heavy rainfall, and viral outbreaks reduce the moth population size.

Answer: Eastern grey squirrel

The larger and more aggressive grey squirrels are able to outcompete the native red squirrels for resources. The grey squirrel also may carry a virus that is fatal to the red squirrel, but does not affect itself. The greys are more destructive to the native environment and are listed among the 100 most serious invasive species worldwide.

In the 1890s they were introduced to country estates for the enjoyment of those living and visiting. One of the worst offenders was the Duke of Bedford, who released and gifted many grey squirrels to other parks and estates from his home at Woburn Park.

As a personal note, when we lived in England, we decided to plant tulips in our planter. We soon discovered that the squirrels had a decided liking for tulips and would dig down 9 inches to dig them out. Cute, but irritating little creatures.

Answer: Rats were nocturnal and the mongoose was diurnal

The mongoose was being used for the eradication rats in the Caribbean. When authorities considered importing mongooses to protect the local cane sugar crop, some local planters in Hawaii requested researching how well that was going and if there were unexpected side effects. These planters were ignored, which led to this embarrassing situation.

Yes, the rats slept during the day while the mongoose was on the prowl. When nightfall came, the rats came out to damage the sugar crop while the mongooses were peacefully asleep.

After the mongoose had been introduced, declines and eradication occurred for many native animals, such as birds, reptiles, and snakes. The mongoose also poses a threat to humans as carriers of diseases, such as rabies.