Think you know everything there is to know about great apes? That's what I thought, too. But then I took a tour around the new great ape house at Stuttgart's Wilhelma zoo and botanical garden - and found out that these fascinating animals still have many a story to tell.
1. The same blood types
Great apes and humans have the same blood types: A, B, AB and O. These types developed more than 20 million years ago; they're something humans and all Old World monkeys share. Even some of the lesser apes like Gibbons have these blood types. The Rhesus factor isn't limited to humans, either.
So in theory, chimpanzees and gorillas could donate blood to humans and vice versa - provided they have the same blood type. The ABO varieties and the Rhesus factor are the most important characteristics that decide over whether a blood transfusion will succeed or fail.
In reality, blood donations are unlikely, though, as humans and apes are different species. Their blood differs in too many details that still need to be investigated.
2. Bonobos have runny noses
These slender, placid great apes are prone to catching common colds. According to one of their keepers, "they cough and sniffle all the time." As a result, the Bonobos at the Wilhelma zoo aren't allowed outdoors once the temperatures drop. Great apes can also easily catch a cold or the flu from humans.
3. Why great apes can't speak
In the movie "Planet of the Apes", gorillas, chimps and orangutans speak like humans. In reality, they can't speak at all because they have a higher larynx, or voice box, which means there isn't enough space between the soft palate and the larynx - the resonating cavity is simply too small. The same is actually true for human babies before they learn to speak. In addition, the great apes' larynx muscles and vocal chords can't move as freely and are therefore hard to coordinate.
4. Communication is possible
Scans of great ape brains show a kind of preliminary speech center. Perhaps that's why they are able to grasp human sign language. Some apes know how to use more than a thousand signs. They can't form complex sentences, but they do create new words. A female gorilla once combined the signs for white and tiger to describe a zebra: a white animal with stripes.
Words other great apes came up with: "ball" and "beans" to denote "peas," "bottle" and "match" to say "lighter," and "bark" in combination with "sky" and "dog" to refer to a helicopter.
A zookeeper told us that gorillas in particular swear a lot if you teach them the signs for swear words.
5. Great apes love TV
At the Wilhelma zoo, US primate researcher Amy Parish studies Bonobos' reactions to TV films. The apes are allowed an hour of movies a day on a large screen on a wall in their compound. The keeper says they (mostly) love this: "When we showed them a documentary from our zoo, they really liked that!" They're really interested in other animals, she adds. What they can't stand is when the zoo vet shows up in the TV program. "The bonobos go nuts - they shake their fists and shriek."
6. Great apes as sex slaves
The fact that great apes resemble humans has its disadvantages for the animals, however: sometimes, they are treated as prostitutes and are being sexually abused, tied down in questionable brothels. Some female orangutans have sad lives indeed.
7. Dangerous moats
Great apes can't swim. As a result, zoos have to think twice about using water-filled moats around their compounds because they could easily drown. That said, Wilhelma chose to build a moat - fenced by an electric wire and complete with a non-swimmer's area - in the new great ape house.
8. The pill
Female gorillas usually don't mate with their closest relatives, their father and brothers. In the wild, when they've reached the right age, they leave their group, and choose a new group with a silverback who appeals to them. The girls make the choice.
When a zoo wants a female gorilla to get pregnant, it passes the female on to another zoo as soon as the animals reach puberty - in keeping with the incest taboo.
Female gorilla newcomers to the Wilhelma are put on the pill. The zoo wants the young gorillas to experience other females having babies and to see how they care for their offspring before they have their own. Great apes learn from their peers how to be good mothers. Rearing children isn't an easy task - for humans and great apes alike.
9. The orangutans' cheek pads
Dominant male orangutans develop large flaps on their jowls that the females are mightily attracted to. In fact, they prefer to mate with well-padded males. The cheek pads are a sign that the male ranks top in the group's hierarchy.
Germany's Wilhelma zoo noted a strange occurrence not too long ago: the highest-ranked male just wouldn't grow cheek pads, and no one knew why. "Then, his keeper was away for six months, and this orangutan developed cheek pads," a zoo worker says. It seems the keeper had the role of the dominant male, and when he was gone the orangutan advanced to the position. You can imagine it wasn't easy when the keeper returned one fine day…
10. More similarities than you would think
All life on Earth is classified in families and species. Chimpanzees and bonobos are of the Pan species; humans are the only living representatives of the Homo species. Both are classified as Hominidae, or great apes. Taxonomically, humans are great apes, too.
Scientists have long been in disagreement over the species Pan and Homo. Many feel the distinction is arbitrary, arguing that humans, chimps and bonobos are so similar that they should all belong to one species, either Pan or Homo. You can imagine that others think that's a bad idea. So for the time being, the separation of the species remains in place.