PORTLAND, Ore. -- Veterinarians think the Oregon Zoo’s pregnant elephant will be having a female baby in a couple months.

Photo by Michael Durham, courtesy of the Oregon Zoo.

Rose-Tu takes a dip in the pool at the Oregon Zoo.

They said hormone analysis conducted on blood samples taken from mom Rose Tu indicate the likely gender.

"We're pretty confident it's going to be a girl," said Mitch Finnegan, the zoo's lead veterinarian, "although I'm still not putting any money on it."

Finnegan explained that typically, testosterone levels would be higher if the baby were going to be male. However, the sample size was fairly small, leaving significant room for error.

 Slideshow: Photos of mom, Rose Tu

 Video: Dad, Tusko 'Father of the Year'

The much-anticipated addition to the zoo's elephant herd, conceived in late 2006, is due to arrive any time from late August to early October. Tusko, a 13,500-pound, 36-year-old Asian elephant, is the father.

Although Rose-Tu is nearly 20 months pregnant, Finnegan said zoo visitors still need to look very closely to spot her "baby bump."

He said the bulge that some visitors have been noticing is actually "part baby, part breakfast" and the result of Rose-Tu's abdominal organs shifting to make room for the baby.

"For many wild animals, the signs of pregnancy are a lot less obvious than they are in humans," he explained.

In the fall of 2006, Tusko was introduced to Rose-Tu in hopes the two would make a love connection. The zoo monitors the female elephants' ovulatory cycles closely and planned the introduction for the appropriate time.

Rose-Tu’s keepers described her as playful and highly intelligent. They hope she will be a doting mother.

As for dad Tusko, “From what we saw that day, [of conception] Tusko was a quite the gentleman, a real 'lady's elephant,' a true Casanova," Finnegan said.

Zookeepers are monitoring Rose Tu closely in light of the 30-percent infant mortality rate among captive Asian elephants.

"There can be complications to both mother and calf,” said zoo Deputy Director Mike Keele. "A calf may be stillborn or get lodged in the birthing canal."

The Oregon Zoo has a renowned breeding program for endangered Asian elephants. More than 25 elephants have been born at the zoo, beginning with Packy in 1962.

Rose-Tu, born Aug. 31, 1994, was the last elephant born at the zoo.

Tusko arrived at the zoo in June 2005 on a breeding loan. He has successfully sired three calves in the past -- two while living in Canada and one in California.