A musk ox at the zoo in Bern has died of acorn poisoning.
Keepers at the Dählhölzli Zoo say the local oak trees this year had what’s known as a ‘mast year’.
It happens every few years when the trees produce vastly more acorns than other years.
Musk oxen are native to the artic and have a highly varied diet in the wild – so too much of the same thing is harmful.
The zoo says it will place a barrier around the trees to keep the animals away.