Armed with a slingshot, Taiwanese bounty hunter Wu Cheng-hua bends sideways and aims his lethal weapon up at a green iguana, one of tens of thousands in the crosshairs of a government cull.

Taiwan's iguana population has exploded since the spikey-backed giant lizards were introduced from Central and South America more than 20 years ago as exotic pets.

Many escaped, or were dumped, and have bred rapidly in the warm climate of the island's south, invading neighbourhoods and ravaging farmers' crops.