Toronto Programs

How Toronto Zoo gets so many baby animals

Does it seem like every week there's a new baby animal video coming out of the Toronto Zoo?

Careful planning and treatment go on behind scenes at zoo's unique reproductive centre

Pandas at the Toronto Zoo respond relatively well to fertility treatments, says the zoo's reproductive physiologist. (Toronto Zoo)

Does it seem like every week there's a new baby animal video coming out of the Toronto Zoo?

It's not quite that often, but there has been an overload of cute animals recently. Whether it's pandas taking their first steps, white lion cubs playing with their father, and just a couple days ago a newborn baby rhino snuggling with its mother.

These births are not by miracle. There's careful planning and treatment going on behind the scenes at the zoo's reproductive centre, the only one in Canada.

Asha, the mother of the infant rhino, was deemed to be "genetically valuable" but had difficulty carrying her babies to term once she was pregnant.

"In her case, we decided to do something that is done with humans and other species, and that is to put her on the hormone progesterone, a very important pregnancy hormone," said Dr. Gaby Mastromonaco. Asha took progesterone daily for a year to help with the 16-month pregnancy.

"We were able to help her sustain the pregnancy and she took this wonderful young male calf to term," she said.

Mastromonaco and her team are in charge of breeding and fertility at the Toronto Zoo. She got the idea to give Asha progesterone based on a successful birth of a baby rhino using the hormone at the Cincinnati Zoo.

Though the birth of the baby rhino was easy for both the mother and infant, the zoo doesn't typically like to get involved in births.

"We prefer zoo breedings to happen as naturally as possible. This is not as common as people think it is," Mastromonaco said.

The zoo's newest addition is a baby rhino, a species currently listed as vulnerable by the International Union for Conservation of Nature. (Toronto Zoo)

The animals viewed by zoo visitors are cross-section of the species the zoo works with. Mastromonaco calls those animals "ambassadors" for the others, not on display. She said there is a lot of work that goes on behind the scenes to ensure there is a diversity of animals at the zoo and on the planet.

"The work we are doing is to ensure these remaining animals with valuable genetic diversity are preserved today, but most importantly preserved for 50 to 100 years from now," she said.

Fertility treatment

The zoo uses different fertility techniques to encourage births among animals that have problems on their own. Mastromonaco recently thawed sperm from a wild bison from 1980 to inseminate a bison.

The zoo has a bank of frozen sperm from approximately 50 different species.

Frozen sperm is less used than hormone analysis, however. 

Mastromonaco runs up to 30,000 hormone samples a year in an effort to understand reproductive cycles, preferences and natural birth tendencies. For instance, if a female isn't producing enough estrogen, the team can help her with estrogen shots, just like with human females going through fertility treatment.

Compared to other animals, the zoo fertility rate is low. One of the most successful animal reproductive rates using artificial insemination is with giant pandas — about 60 per cent. It's generally around a 30 per cent success rate for other species to get live offspring.

Compare that to cows, which have a 90 per cent success rate with artificial insemination.

Still, the results have been good, in Mastromonaco's opinion. She said this past year in particular has been great for mammals.

On a personal level, Mastromonaco said her work is incredible and she learns something new about animals every single day.

"Sometimes I wake up out of whatever I'm doing and I look around and I realize, oh my god, I'm in a room with a tiger," she said. "Every day is a spectacular day."


  • A headline on an earlier version of this story suggested incorrectly that a panda at the Toronto Zoo received estrogen. In fact, it was a mother rhino that received hormone treatment in the form of progesterone.
    Feb 23, 2016 8:25 AM ET