SNA (Taipei) — Thousands of invasive iguanas up to 1.5 meters long are spreading in Taiwan, with authorities complaining that pet owners abandon the reptiles when they grow to look like dinosaurs.

Reptile hunters are racing to catch the striking South America and Central America-native green iguanas before they cause more harm to agriculture and the environment.

For the first time, the annual number of the iguanas caught and killed in Taiwan exceeded 10,000 last year. The annual catch rose from 527 in 2016 to more than 14,500 in 2020, according to Council of Agriculture statistics.

The hotspot is Pingtung, a tropical, agricultural county in Taiwan’s south, where 8,570 of the pesky lizards were hunted down.

The county government called the numbers being caught “astonishing,” and said it was difficult to estimate how many were living in the wild.

Tien-hsi Chen, a professor who has been running a program to monitor and control the green iguanas since 2013, said that they had no empirical data to say that the populations of invasive iguanas were growing. However, the geographical areas in which they are found has expanded rapidly in recent years.

“With limited budget and manpower, it is impossible to control the expansion of the feral populations of green iguanas in southern Taiwan,” said Chen, of the National Pingtung University of Science and Technology’s Institute of Wildlife Conservation.

The green iguanas eat insects and bird eggs when young. But as adults, they move on to leafy crops, flowers, and fruits, and they build nests by digging holes on the sides of waterways. This can damage river embankments and drainage ditches and affect irrigation.

They have no natural predators in Taiwan, and can multiply quickly; the female of the species can lay 40 to 70 eggs per year, and on average more than 80 percent of these hatch.

Chen said it had become “an issue of economy and food security.”

“In southern Taiwan, green iguanas consume commercial and village vegetable, crops, ornamental and horticulture plants,” he said.

“Furthermore, the socially disadvantaged farmers or residents are particularly vulnerable to invasive green iguanas due to (their feeding) extensively on the small-scale and semi-subsistence farming.”

Elsewhere in Taiwan, the striking creature has also been making waves. In Changhua county in central Taiwan, one YouTuber uploaded a video of him and his family using slingshots to kill more than one hundred iguanas in a single day.

Anyone owning a green iguana now has to register with authorities or face a fine up to NTD50,000 (US$5,400).

The Pingtung County government says the species was initially introduced to Taiwan as a pet, but that the creatures have repeatedly been abandoned into the wild by their owners.

“When it matures, it becomes unwanted because its body is huge and it strongly resembles a dinosaur,” the government said in a statement on its website.

Chen said that imports of green iguanas could be traced back to the 1980s, but that these soared in numbers after Taiwan lifted a ban on the trade of captive-bred green iguanas in 2001.

Given that the iguanas feed on plants and aren’t actively aggressive to people, “residents or local governments usually ignore the potential impacts of iguanas in the early stage of invasion,” Chen said.

Also known as the American iguana, the sharp-toothed creatures can use their tails to deliver blows. If grabbed, the tail can break off and regenerate.

Hunters in Pingtung County catch the larger iguanas–which can grow up to 1.5 meters–with a wire noose attached to a telescopic landing net handle. They use a noose attached to the end of a fishing pole to trap newly hatched and younger ones.

The county government spokesman said they disposed of the iguanas “humanely,” but gave no details.

The public has been encouraged to catch green iguanas in return for agricultural products. This has led to a gradual increase in the numbers of people catching them, and therefore the numbers being caught has also risen, the county spokesman related.

Authorities in Pingtung say there is no need for anyone to panic if they discover a green iguana inside or outside their home. Instead, they can call for help via a county hotline, or try to catch it themselves with a bucket or cardboard box while “being careful not to be bitten.”

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