GERMAN zookeepers have been left baffled after their 130lb chimps went bald - but there's a sinister reason behind their new fur-style.
The apes' ultra-ripped physiques are on display reportedly because the "stressed" animals tore each other's hair out in a savage display of strength.
Horror pictures from Magdeburg Zoo, in northern Germany, reveal some chimps with hair hanging in shreds off their backs and others with no hair at all.
A notice next to the chimpanzees' sad-looking enclosure explains that their frightening appearance is due to "over-grooming".
In the primate kingdom, grooming is used to show affection and confirm their ranking.
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However, it appears to have got out of hand at Magdeburg where animal rights activists have been sounding the alarm about chimps' abnormal behaviour.
Peta have complained that the apes showed "symptoms of severe psychological stress disorders".
They argued: "Some of them had noticeable bald spots on their heads, chests and the back of their shoulders; some were now almost completely hairless.
"In addition, some animals consumed their own excrement."
Peta claimed that their "behavioural disorder" indicated "significant, ongoing suffering".
According to the animal rights organisation, the so-called "overgrooming" is a result of stress, fear, boredom and frustration - all triggers for chimpanzees behaving strangely.
The running theory for what's behind their psychological stress is their small enclosure.
In 2019, a mass ape jail break from their large outdoor enclosure saw them moved into a smaller caged area.
The zoo has spent £1.6million building an escape-proof site but it will only open later this year.
Magdeburg Zoo veterinarian Felix Huseman told German outlet Bild: "Our animals are doing very well health-wise."
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Peta already launched a criminal complaint in 2021 against the zoo for closing the ape's large outdoor enclosure but it was later dismissed.
Now, the animal rights activists have filed a complaint against the prosecutor's office ending the investigation and are demanding a final decision over the court proceedings.
“We appeal to politicians and the zoo to completely phase out the captivity of great apes in the Magdeburg Zoo,” Peta said.
“It is a crime to imprison great apes," spokesperson Dr Yovnne Würz added.
In 2021, The Sun told of terrifyingly muscly chimps bearing razor-sharp fangs that were suffering from alopecia.
The primates brutally beat each other up, prompting some to believe they could take over the world in a Planet of the Apes-type horror.
The hairless beast were filmed as they ran rampant around an enclosure ganging up on the weak.
It comes as an army of sex-crazed monkeys terrorised a city after indulging in buffets of sugary drinks and snacks in Thailand last month.
The rampaging macaques are thought to have been made hyper-sexual and violent as they rampaged high on sugar at an annual festival.
The city of Lopburi was completely overrun by some 3,500 monkeys, with certain parts deemed complete no-go zones due to gangs battling for supremacy on the streets.
