The Calgary Zoo says a baby giraffe died because it had an underdeveloped urethra and wasn't able to urinate properly.

"Basically, he was not able to urinate normally and therefore there was a buildup of urine which led to toxins just being built up in his body, which would have caused his death," said Jamie Dorgan, the zoo's director of animal care.

The giraffe was less than a week old when it died last weekend.

It was smaller than expected when born to mother Emara.

Emara was brought to the Calgary Zoo from San Diego in 2016 as part of a breeding program.

She had previously had two late-term miscarriages and a calf that died after 48 hours.

This time around, Emara received progesterone supplements — a treatment apparently not tried on a giraffe before. Progesterone supplements are commonly provided to women, as well as domestic animals, with a history of miscarriage.

Dorgan says the urethra issue was a birth defect that only became apparent during the necropsy.

"We had been monitoring them, obviously, consistently since he was born, and we did notice he seemed a little depressed on the evening before he died," he said.