When proud parents-to-be Brad Pitt and Angelina Jolie played cat-and-mouse with paparazzi in Africa, they had some big cats on their side.

The stars were spotted at an airstrip returning with kids Maddox and Zahara from a game reserve, where wild lions roaming the grounds reportedly helped keep prying photographers away.

It's believed by some observers that Pitt and pregnant Jolie went to Namibia for the birth of their child so Maddox, 4, and Zahara, 15 months, will have a brother or sister who's a citizen of an African nation.

You might want to bet on a sister. On its Web site Wednesday, People magazine quoted an observer who overheard Jolie saying, "We think it's a girl, but we're not 100 percent certain."

Before flying to Africa nine days ago, Pitt and Jolie bought baby dresses, socks, a bonnet and a layette, while on a shopping spree in a Paris boutique.

But the couple also picked up a gray T-shirt with the word "boy" on it, just in case.

Jolie, 30, has filmed a movie in Africa and traveled there many times in her role as a goodwill am bassador for UNICEF.

Pitt, 42, joined his gal pal in Ethiopia to adopt Zahara in July. Maddox was adopted by Jolie in Cambodia.

Their baby, the couple's first biological child, is reportedly due May 18.

Earlier reports speculated Jolie was going to give birth in France, where her mother is dying of cancer.

Since their arrival in Africa, where they've been staying out of sight in a lodge near a beach, security has been very tight.

Namibian officials have reportedly threatened to kick out foreign paparazzi -- at least those who haven't been eaten by the couple's four-legged bodyguards.