A number of critically endangered and near-extinct species were among 55 animals that died at Dublin Zoo in 2016, according to internal records.
These included both of the zoo's male western lowland gorillas, a giraffe, three white-naped mangabeys and an Amur tiger - of which there are only a few hundred still living in the wild.
The latest figures show that more than 11pc of Dublin Zoo's animal population died during 2016, bringing the total number of deaths at the popular attraction to 164 during the three-year period from 2014 to 2017.
Animal inventory records obtained under the Freedom of Information Act reveal there were also 93 births at the zoo in 2016, however, one-in-four of these died within 30 days.
A scimitar-horned oryx, a species of antelope that has been extinct in the wild for almost 20 years, also died at Dublin Zoo last year. A total of five of these animals died at the zoo between 2014 and 2017.
Two adult Waldrapp ibis - described on the Dublin Zoo website as "one of the most endangered birds in the world" - died in 2016, along with a citron-crested cockatoo, of which there are under 5,000 worldwide.
The most high-profile animal death in 2016 was that of Harry the gorilla, who died after a stroke on May 29. His death featured last year on the RTE series, The Zoo.
The western lowland gorilla, one of a critically endangered species, was 29 years old when he died. Their average lifespan in the wild is 35-40, although they can live for more than 50 years in captivity. These were replaced by a new male and female, while a baby gorilla was born in July 2016.
Other animals that died at the attraction in 2016 included a grey wolf, a Humboldt penguin and a baby snow leopard.
A spokesperson for Dublin Zoo said the well-being of animals is its "number-one priority", and that ensuring every animal lives out its life to the full is "paramount".
"However, as in the wild, animals die in Dublin Zoo. In every situation, the best of veterinary care and attention is given," they said.
The spokesperson said Dublin had a "world-class zoo" that had developed "best-in-class" habitats over the past decade.
"Between 2014 and 2017, Dublin Zoo had 263 births, many as a result of Dublin Zoo's role in international breeding programmes to ensure survival of some of the world's most endangered wildlife."
However, a representative of the National Animal Rights Association said the latest death figures were unsurprising.
"Unfortunately, it is not surprising," they said.
"Animals do not thrive in zoos, and these losses are proof we should be focusing on protecting animals in their natural environments - not in enclosures built for humans' entertainment."