Edinburgh Zoo penguin Mrs Wolowitz is thought to be the oldest of her species in the world

A Edinburgh Zoo penguin is thought to be the oldest of her kind in the world after celebrating her 35th birthday.

Mrs Wolowitz northern rockhopper penguin at Edinburgh Zoo Pic: RZSS / Saltire News

Northern rockhopper Mrs Wolowitz hatched in 1987 and has lived to double her life expectancy.

She was presented with a birthday treat of her favourite sprats and whitebait by keepers at Edinburgh's famous penguin colony.

Rockhoppers – among the smallest penguins and known for their bright yellow head plumage and red eyes - usually live around ten years in the wild and around twice that age in captivity.

Age is just a number for Mrs Wolowitz Pic: RZZS/Saltire

Dawn Nicoll, senior animal keeper at Edinburgh Zoo, said Mrs Wolowitz was "extraordinary".

She said: "Mrs Wolowitz hatched at Edinburgh Zoo so she's always been with us and in fact she's older than most of her keepers.

"She only had one chick, a wee male we called Mr Green, but she outlived him and she's still going strong.

"We all have a soft spot for Mrs Wolowitz. She always gives us a honk when we arrive in the morning and then when we shout 'goodnight' at the end of the day.

Age is just a number for Mrs Wolowitz Pic: RZZS/Saltire

"She also has a bit of a fan club among our visitors, who look out for her in her favourite sunny spot.

"But she can be quite feisty. She'll stand her ground with the juvenile penguins and isn’t afraid to tell them off if they are in her space or annoying her.

"She is also known to barge to the front of the queue at feeding time. She enjoys sprats but she's particularly partial to the whitebait we give to our chicks, so that's a rare birthday treat for her."

Edinburgh Zoo is home to more than 100 penguins including three different species - king, gentoo and northern rockhopper. There are currently 24 rockhoppers, including two recent chicks.

The Zoo describes Mrs Wolowitz as "the oldest and sassiest penguin in the colony".

Mrs Wolowitz hatched on 13 May 1987 and produced her only offspring, Mr Green, in 1991, when she was four years old.

The pair were inseparable and Mrs Wolowitz was named at that time after a mother character in the TV sitcom The Big Bang Theory, dedicated to her son, Howard.

Mr Green reached the age of 25 before he passed away in 2016.

Dawn said some of Mrs Wolowitz' feathers were now greying in her old age and she has cataracts but is otherwise defying her old age.

She suggested that the penguin's longevity may be down in part to only having had one chick.

She said: "There may be an element of that because having chicks year after year can be quite stressful."

Despite her seniority, Mrs Wolowitz isn't the most famous penguin at Edinburgh Zoo. That accolade is reserved for 20 year old king penguin Sir Nils Olav III, the famed mascot and colonel in chief of the Norwegian King's Guard.

Dawn added: "Sometimes Nils goes over and sings to Mrs Wolowitz, but if he gets too close she swiftly tells him to back off."