Three animal deaths at the Pittsburgh Zoo & Aquarium this month have brought “profound sadness” to its staff, officials said Monday during a news conference.

“This is a lot for our staff to deal with right now,” said the zoo’s president and CEO Jeremy Goodman, “It is very tough when visitors come up and constantly ask what happened. It is a very trying time.”

Three animal deaths coming in a short time period has left the zoo’s staff reeling. It closed its doors on Feb. 17, a Saturday, as staff members mourned the losses.

Still, it’s normal for a zoo to lose 15 to 25 animals a year, Goodman said. The Pittsburgh zoo has had five animal deaths since July.

The number of deaths the Pittsburgh Zoo has reported over the last year falls within an expected range for a facility with a large animal collection, said Jill Nizan, director of conservation operations for American Humane, a

Washington organization committed to helping ensure the safety, welfare and well-being of animals.

Mrithi, the first-ever gorilla born at the zoo, died earlier this month at age 31. A male silverback Western lowland gorilla, Mrithi had recently been showing mobility problems, with spinal issues the likely suspect, according to a zoo curator.

A 2-year-old elephant calf named Tsuni died after a sudden and brief battle with a disease at the International Conservation Center in Somerset, the Pittsburgh Zoo & Aquarium announced Feb. 15. Elephants from birth to age 8 are at highest risk for the disease, with an 85% mortality rate, a zoo spokesperson said at the time.

Then, an 18-year-old sea lion died while under sedation to diagnose an illness.

Goodman said zoo life mirrors human life in that they celebrate births and milestones.

“The zoo world is no different than the human world in that regard,” said Goodman.

Only recently have they been sharing tragedies and deaths are something very new to the zoo, Goodman said.

“Our staff’s well-being is still one of most important things we are concerned with right now, and that includes their mental health, which is why we closed two Saturdays ago.

Goodman said the zoo provided grief counselors all last week to help staff.

The Pittsburgh Zoo is one of six major zoo and Aquarium combinations in the U.S. and operates the only center in North America that focuses on the breeding and care of African elephants. It is home to more than 8,000 animals representing more than 600 species.

When the zoo closed, guests who prepaid for tickets were notified to make alternative arrangements.

“This has been a difficult time having lost these cherished animals,” said Ron Gruca chief advancement officer for the zoo. “We take this very seriously. We apologize for the delay in this briefing. We are committed to public transparency.”