Officials at the Denver Zoo have helped hatch four Komodo dragons, and another four eggs could be on the way in a monumental achievement for continuing the species, which is endangered on its native islands in Indonesia.

“This is a very significant event, as Denver Zoo is only the second zoo in North America to hatch dragons this year and the only zoo in the world to hatch dragons on three different occasions,” curator of reptiles and fishes Rick Haeffner tells Fox 31.

The baby dragons, which can grow to 10 feet in length and weigh more than 250 pounds, will be on display in the zoo’s Tropical Discovery nursery around the time of the Zoo’s Halloween celebration, Boo at the Zoo. Just thousands of the lizards are left in the wild, and they also remain rare at zoos.