Nature's bizarre bone quiz

Bizarre bone quiz

Secrets of Bones begins on BBC Four on February 18, 2030 GMT and looks at the evolution of skeletons throughout the animal kingdom. Test your knowledge of some of the most bizarre bones with our quiz.

Ben Garrod and skeletons

1.) Question 1

Each of these bones comes from a different species but they are found in the same part of the body. Which appendage?

Bones on a wooden table
  1. Tail
  2. Penis
  3. Arm

Penis bone facts

Penis bones are found in many animals including seals, most primates and dogs (pictured). Humans rely on blood pressure for an erection, but for animals with a penis bone, muscle contractions slide the bone out of the abdomen in to the penis to keep it rigid.

Bone and fifty pence piece

2.) Question 2

Which of the following is not a recognised name for a penis bone?

  1. baculum
  2. oosik
  3. coccyx

3.) Question 3

Great apes do not have bones in their penis.

  1. True
  2. False

How they help

Penis bones help to deliver sperm by providing a rigid structure. And instead of waiting for blood flow, animals with penis bones can quickly contract their muscles to mate very quickly which can be helpful in competitive environments. Scientists also suggest the bone could stimulate females to be more receptive of sperm or to release eggs.

4.) Question 4

The biggest recorded penis bones belong to which animal?

  1. Elephant
  2. Elephant seal
  3. Walrus

5.) Question 5

Not all penis bones are straight. Which animal does this curved one belong to?

Curved penis bone
  1. Raccoon
  2. Dog
  3. Monkey

6.) Question 6

Size mattered to ancient *

  1. Lion
  2. Bear
  3. Seal


  1. Males in around 80% of mammal species have a bone in their penis.
  2. Penis bones are also known as baculum, the Latin for stick, and as oosik in Alaska where they are used in native art.
  3. Humans are the only great apes that do not have a bone in their penis. Our closest relatives, chimpanzees, only have a baculum the size of a grain of rice.
  4. A walrus's baculum can reach over 60cm long - as long as a human thigh bone. The longest ever recorded belonged to an extinct species of walrus and measured 1.2m.
  5. In racoons, the distinctive hook shaped bone complements the shape of the female's pelvis.
  6. Indarctos arctoides, an extinct species of bear from western and central Europe, had a baculum that reached an average of 23cm. It was longer than that of its huge cousin the polar bear.

Your Score

0 - 1 : Bone idle

2 - 3 : Bone up

4 - 5 : Bone daddy

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