Sparky the hippo, 26, delivered stillborn twins at the Calgary Zoo on Friday Jan. 3, 2013. She was on birth control so the pregnancy was a surprise.

Image Credit: Calgary Zoo

CALGARY - The Calgary Zoo says a hippopotamus has delivered stillborn twins — an event which came as a surprise to zoo keepers who didn`t know the animal was pregnant.

The zoo says in a news release that Sparky, a 26-year-old river hippo, gave birth to the nearly full-term fetuses on Friday afternoon.

It says staff tried in vain to resuscitate them, but a necropsy revealed they both died just prior to delivery.

The zoo says the cause was likely twisted or entangled umbilical cords.

Zoo curator Colleen Baird says staff had noticed Sparky was putting on weight and acting differently, but didn't think she was pregnant because she has been on birth control for a number of years.

Baird also says her age, as well as the immaturity of the male hippo at the zoo, made the pregnancy unlikely.

"We were becoming suspicious that she was pregnant because of recent weight gain and some behavioural changes, but we thought it wasn't possible," Baird said in the news release. "It appears nature had other ideas."

Baird said twin births are extremely rare in hippos and the likelihood of both surviving would have been very small.

The gestation period for hippos is eight months.

Sparky was born on May 30, 1987 in Toronto and arrived in Calgary on September 22, 1988.

The zoo's male hippo, Lobi, was born on October 31, 2006 at the Granby Zoo in Quebec.

Both hippos were forced out of their African Savannah exhibit in Calgary by severe flooding that hit southern Alberta in June.

Water levels rose high enough for the herbivores to swim over the top of their enclosure and roam freely about the African Savannah building.

Zookeepers feared they could swim out of the building onto zoo grounds and escape, but staff put up barriers to contain them.

The zoo says this was the fourth pregnancy for Sparky although her previous calves were sired by former zoo resident hippo, Foggy.

Her first calf in 1991 was also stillborn.

Baird said that while the likelihood of both twins surviving would have been small, the zoo would have liked the chance to help Sparky try to raise them.

"This is very, very sad for our team. Our priority now is making sure that Sparky is alright," she said.

Image Credit: Calgary Zoo

News from © The Canadian Press, 2014