HOUSTON – Tess, one of the nine Asian elephants at the Houston Zoo, is pregnant and is due this summer, zookeepers announced Friday.

PHOTOS: Houston Zoo elephant to give birth this summer, zoo says

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In a video posted on Facebook, zookeepers said the 35-year-old elephant has been pregnant for nearly two years, which is the average gestation period for Asian elephants.

Zookeepers said they have used ultrasounds to track the progress of Tess’ pregnancy. They will soon start drawing blood to track hormone levels, which will better determine when she will give birth.

Tess will give birth in the McNair Asian Elephant Habitat cow barn under the supervision of her keepers and veterinary staff. After delivery, she and the calf will undergo post-natal exams and spend several days bonding behind the scenes. The elephant team looks forward to watching the pair share several key moments that will prepare them for their public debut. Nursing, communicating with mom, and hitting weight goals are important milestones for a growing baby elephant.

This is not Tess’ first calf, though. Her last baby was 7 ½-year-old Tupelo, who is also housed at the zoo. Tess’ son Tucker, who is now 13 years old, came with his mom when she arrived at the zoo.

This will be the second baby elephant the zoo has had in just more than a year. Joy was born to 26-year-old Shanti last summer.

Zookeepers said Joy, now 10 months old, is doing well and weighs nearly 1,200 pounds.