This is the second diary entry in a series.

There's no Mother's Day surprise for Chai, Woodland Park Zoo's pregnant elephant: The gender of the calf she's carrying remains a mystery.

Tests done by a Missouri zoo that would have measured a testosterone surge in Chai's blood so far have had a problem reading the serum. If it's a boy and he stays at Woodland Park, the zoo will have to build a separate bull facility. Now it appears the zoo may have to wait until fall to learn the baby's gender the old-fashioned way.

Meanwhile, as Chai reaches the 16th month of her 22-month gestation, there are plenty of other mysteries.

Assuming the birth of a healthy calf this fall, how will Chai, 24, be as a mother?

Will the three other elephants - Sri, Bamboo and the lone African elephant, Watoto - serve as aunties, or will they find the baby irritating?

Since there's never been an elephant birth or even pregnancy at Woodland Park, there's no way to know whether the zoo's four females will have the same maternal instincts as elephants in the wild.

"I guess Watoto is the closest thing we've ever had to a mother," said veteran keeper Chuck Harke, who said it was love at first sight for the emotional Watoto when Chai arrived as a 1-year-old in 1980. "It was amazing."

In the wild, when an elephant baby signals distress with a cry, all the female elephants in the herd run to its aid. As a yearling, Chai learned to use that cry to her advantage, shrieking when she was handled by keepers, which brought Watoto at a dead run.

"You get 8,000 pounds running at you and it's pretty scary," Harke recalled.

That relationship never changed. Watoto, the perfect protector as dominant elephant, continues to favor Chai, even sharing food treats.

But the keepers know instinct doesn't guarantee the herd will accept Chai's baby. When Sri (pronounced See) arrived as a yearling, one year after Chai, nobody protected her. In fact, she was frequently bumped around.

One goal of having animals reproduce in captivity is to offset their fast disappearance in the wild. Another is to make life more closely resemble real life by encouraging naturally occurring social units.

Female elephants in the wild form a circle facing outward so they can tuck babies inside in times of trouble.

Lead keeper Pat Maluy has seen Woodland Park's elephants "circle the wagons," even without a baby, which gives him hope they will behave around Chai's baby as they would in the wild.

But if Chai's baby learns to cry "wolf" as Chai did, Harke has one piece of advice:

"Get out of the way."