A healthy cub was born to a Sumatran tiger Sunday afternoon at the San Francisco Zoo, authorities announce.

The cub, who has not received an official name yet, was born to 9-year-old Sumatran tiger Leanne and her 6-year-old partner Larry. Junior's father Larry was flown in to sire Junior from New Orleans. Officials will be able to reveal the sex of the cub after an examination that will be conducted only after two or more weeks. Referred to as 'Junior', the officials say it is active and healthy.

On Feb. 13, the zoo authorities tweeted saying, "Congrats to our Sumatran tigers Leanne and Larry on the birth of their cub last Sunday!!"

"We really prefer to allow mom and cub to have a really solid two-week bonding time before we get involved," Corinne MacDonald, curator of carnivores and primates at the zoo, was quoted as saying in SFGate."It wiggles a lot and squirms a lot. The active part is what we really look for right now."

Leanne and Larry's cub 'Junior' is the first tiger to be born at the San Francisco Zoo since 2008. Prior to this, Leanne littered three male cubs in 1976 and they were later transferred to zoos across the United States.

According to MacDonald, the mother is doing a fabulous job with her newborn. She is being an attentive and caring mom.  She has been seen grooming Junior, who makes sounds, screams and cries when it gets hungry. The cub also coos.

It is only after a month that visitors can have a look at Junior. But those animal lovers who can't resist seeing the cute little cub are flocking to social sites like Facebook and Twitter to view the cub's photos.

The birth of the rare Sumatran tiger is a rise to the population, which was listed as an endangered species by IUCN in 2008. They belong to the Sunda Island group of tigers and are the only ones surviving. They are found in the Indonesian island of Sumatra.