Two critically endangered Sumatran tiger cubs born at Washington zoo

(Reuters) - Two Sumatran tiger cubs have been born at the national zoo in Washington, D.C., and by Thursday they were crawling over their mother "as if her body is a jungle gym," the zoo said on its website on Thursday.

The cubs' birth on Monday night was heralded as a conservation success since Sumatran tigers are critically endangered in the wild, where fewer than 500 remain, according to the Smithsonian National Zoological Park website.

"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.

Their mother, Damai, a 4-year-old tiger, and father, Kavi, a 12-year-old tiger, bred several times, a zoo spokesperson said.

Keepers confirmed her pregnancy on June 21 and prepared for the cubs' arrival after she became restless and showed signs she would soon give birth, the website said.

The newborn cubs, their eyes still shut, have spent their days being groomed and nursed by Damai, a first-time mother, the website said.

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

The cubs mostly likely will not be on exhibit until fall, but they can be viewed online through a set of webcams in the tigers' den.

(Reporting by Barbara Goldberg; Editing by Nick Zieminski)