Gray’s monitor lizards had long been considered extinct in the wild until some were discovered in 1975 on islands in the Philippines.

The species is considered one of the largest lizards in Asia, as the reptiles can grow to be 6 feet long and 20 pounds. The tree-dwelling, olive-green lizards usually dine on fruit and invertebrates.

The zoo’s reptile and amphibian curator, Ian Recchio, said his staff used their knowledge of other Asian monitor species and Komodo dragons to hatch the Gray’s monitor eggs.