BROOKFIELD, Ill. (AP) — A giraffe that officials of Brookfield Zoo outside Chicago describe as being the matriarch of the zoo's herd has been euthanized.

Mithra at age 27 was one of the oldest giraffes in an accredited North American zoo. Officials say the giraffe was affected by degenerative changes in her joints and physical condition, symptoms encountered by all species as they age.

Although her care over the last year allowed her to "remain comfortable and able to still be with the other giraffes," her condition declined recently. That forced the zoo to make the decision to euthanize Mithra, officials announced Thursday.

Zoo officials say she "will be greatly missed."

There are four giraffes now in the Brookfield Zoo herd.