Two Sumatran tiger cubs were born at the National Zoo in Washington, DC on Monday, the zoo announced Thursday. The birth of the cubs marks a conservation success for the critically endangered tiger species.

Fewer than 500 Sumatran tigers remain in the wild, according to the Smithsonian National Zoological Park website, Reuters reports. There are only 65 living in accredited zoos in North America, according to The Washington Post.

"All I can do is smile because the team has realized our goal of producing critically endangered tiger cubs," said National Zoo biologist Craig Saffoe.

This is the first litter for the zoo's 4-year-old female Sumatran tiger, Damai. The cubs' father is the zoo's 12-year-old male Sumatran tiger, Kavi. Kavi, unlike Damai, has bred several times, a zoo spokesperson told The Washington Times. Damai came to the zoo in 2011, and Kavi arrived a year ago.

In zoos, Sumatran tigers can live up to 20 years, though their lifespan is around 15 years in the wild, UPI reports.

Damai and the cubs will not be exhibited publicly at the zoo for several months. They must undergo a series of health exams and get vaccinations, the zoo said in a statement.

Tiger fans can watch the cubs on the zoo's live webcams, set up in Damai's den. Kavi can be visited at the Great Cats exhibit.

The cubs, which have yet to be named, each weigh about two pounds and haven't opened their eyes yet. They won't be able to do so for a few weeks, when they are more mobile, UPI reports.

Despite this, the website said the cubs are healthy and happy.

"Damai lets the cubs crawl all over her, as if her body is a jungle gym," the website said.

"It's really special to see her become a great mom," Saffoe said.