Southern Taiwan continues to battle invasive green iguanas

南台灣持續對抗入侵綠鬣蜥

Pingtung County Government removes 23,000 green iguanas in first nine months of year


TAIPEI (Taiwan News) – Invasive green iguanas have spread across southern Taiwan, with a Pingtung County Government removal program capturing 23,000 iguanas in the first nine months of the year.

Chen Tien-hsi (陳添喜), a professor at the National Pingtung University of Science and Technology’s (NPUST) Institute of Wildlife Conservation, said green iguanas first appeared in Pingtung 10 years ago and have since spread to almost every part of southern Taiwan. Cheng believes their rapid growth requires the government to reconsider its current management and control strategy, per UDN.

Chen said green iguanas eat sweet potato leaves, loofah flowers, vegetable seedlings, bean seedlings, and peanut seedlings. The voracious appetite of green iguanas is beginning to affect crop outputs.

Researchers from NPUST assist farmers in trapping green iguanas with fermented fruit. Green iguanas are attracted to fermented fruit, especially overripe mangoes and papayas.

Chen said green iguanas are from the tropics and fear the cold. Warm winters with less rain can lead to more reproduction. Green iguana eggs become damaged if soaked in water, with heavy rainfall affecting hatchability.

According to Chen, green iguanas breed once a year, with eggs laid from mid-March to the end of April. Rising water levels from typhoons can also wash green iguanas downstream or offshore. Chen said this could lead green iguanas to soon appear in towns along the west coast.

Green iguanas are herbivorous, with a diet including leaves, flowers, and fruits, and they occasionally prey on insects. Although they can prey on small lizards, baby birds, and eggs, this type of feeding has not been observed in Taiwan.

Chen cited the example of a green iguana removal program in Grand Cayman. While it's only one-third the size of Taipei, green iguanas, first introduced to the island 40 years ago, have doubled in numbers every 1.5 years, with the population reaching one million in 2018.

Grand Cayman's green iguana population had reached a level where more than 60 green iguanas could be spotted in trees, while they also frequently climbed telephone poles and damaged power lines. Finally, Grand Cayman allocated NT$300 million (US$9.3 million) to capture more than 1.4 million green iguanas.

Chen said Grand Cayman’s successful cull was due to clear goals and objectives. While he said the chance of complete eradication is quite low, reducing their numbers is entirely possible.

Chen said the survival rate of young green iguanas in the first year is about 5%, and the survival rate after the second year is between 70 and 80%. Female green iguanas lay between 15 and 80 eggs, which grow and mature rapidly.

According to Chen, catching female green iguanas should be a priority, resulting in fewer babies the following year. Compared to other lizards, green iguanas have a long lifespan that typically extends for more than nine years in the wild.

In addition to training qualified personnel to assist in removal, Chen said the public should also become involved by reporting the whereabouts of iguanas. With more detailed data, the effectiveness of removal campaigns can be improved, limiting the impact of this invasive species on Taiwan’s environment.