One of the original residents of Colchester Zoo has died, it has been announced.

Chimpanzee Billy-Joe, who was described by the zoo as ‘part of the original zoo family’ passed away on Thursday, March 1.

Keepers became concerned for the chimp, who was more than 40 years old, when they noticed she wasn’t using her right leg and had swelling around her ankle.

Due to Billy-Joe’s age and the risks involved with anaesthetising her, vets initially prescribed some treatment to make Billy-Joe more comfortable and assess her the following day.

Unfortunately, there was no sign of improvement so the decision was made to anaesthetise Billy-Joe for a medical examination and take x-rays to determine the problem and what course of treatment to take.

The examination revealed the monkey was suffering from a blood clot stopping the blood circulation to her foot.

Treatment was prescribed to break down the clot and to reduce the likelihood of further clots developing. But sadly Billy-Joe still continued to not use her leg.

After following a course of medication Billy-Joe was not showing signs of any further improvement and so on Thursday it was decided to put Billy-Joe to sleep.

A statement on Colchester Zoo’s Facebook page said: “Billy-Joe came to Colchester Zoo in the late 70s aged approximately six years;she arrived at the zoo with few details about herself, indeed just a name.

“Since living at Colchester Zoo, Billy-Joe became a mother to Tara and Kora, grandmother to Tekita and great-grandmother to Tumba and Talia.

“Billy-Joe leaves behind a great legacy and was one of the zoo’s most treasured animal friends who will be greatly missed by many loyal supporters of the zoo who regularly visited her but especially and most sadly missed by her dedicated keepers who she had a wonderful relationship with and all those that have cared for Billy-Joe since she came to Colchester Zoo.

“Billy-Joe will always be at the heart of Colchester Zoo’s family.”