Skeletons in my Closet
by Bob Church
Q: "Do you know much about the ferret's skeleton? How are they different from people? Are their legs short or are their backs long?
A: Neither.....they're telescoping. Ok, who paid you to ask this? I'll try to muddle through this one, but there will be a quiz at the end.
The skeleton of all mammals is basically the same, so if you study one, you study them all. Humans have about 204 bones in their skeleton, however, it actually runs between 196-214 depending on what you include. Younger mammals can have 2-3 times more bones than adults, but they ultimately fuse together. If you look closely for differences in the ferret skeleton, you will find some of the vertebrae are a little bit longer (proportionately) than in most mammals.
This is especially true of the neck vertebrae. The limb bones are a little bit shorter than in most mammals. Finally, the skull of ferrets is very long compared to most mammalian skulls. You know what a human skull looks like. Imagine someone flattening the top of your skull until it was level with your eyebrows, then pulling your nose and jaw out, say 7 or 8 inches so you can no longer see anything under your nose. Now, pull the back of your head and stretch the skull almost a foot. You now have the human equivalent of a ferret skull. Cool. Now, find a San Diego Padres ballcap that fits.
The end result of each vertebrae being a little longer than usual (plus the long skull) is a body that is proportionally quite long. Shorten each leg bone a little, and you magically have the ferret, adapted to run down tiny tunnels, and still be able to carry their catch without tripping over it. Imagine a dachshund trying to carry another dachshund in its mouth and get somewhere fast. Those legs would trip over something with every step and the weinie dog would get nowhere fast. But add a long neck, and now the loser can be carried enough forward to keep out of the way of the victor's feet. Trim those ears a bit, and tie something stinky to it's butt, and you have a really funny looking dog disguised as a ferret. Wanna bet the CaCa Fish and Gestapo will outlaw them?
The skull is long and flat for several reasons. First, it makes for a powerful biting force, proportionately one of the strongest in mammals, which is very useful in killing animals near your size having teeth that can bite through a pencil (hey, imagine a giant beaver snapping at your nose, with incisors as thick as your middle finger). It also turns the body into a streamlined tube, which is really neat when running down tunnels and you don't want to bump your head or need to turn around really fast. It also puts your teeth right out in the front. Open those jaws and all you see are teeth. White gleaming teeth, sharp and pointed, coming at you, with this awful stink and a loud hissing. Ooooooooo! The next D-grade horror film from the Ca Ca Fish & Gestapo.
Arm bones: The ferret clavicle is a tiny little ossification in the muscle where the clavicle should be, and is not always found, but the scapula, humerus, radis, and ulna are about the same as ours. Their elbow has an extension on the end of it to make their arms very strong for digging. The wrist bones (carpals), the hand bones (metacarpals), and the finger bones (phalanges) are almost the same, except for the 3rd phalanx which has a claw-like process on the end to support the nail. Ferrets have more carpal-metacarpal sesamoids than we usually do, which are tiny bones within the tendons where they pass over joints. Most of us have 1 or 2 of them at our thumbs, but ferrets generally have 2 for every digit. Oh, the thumb has 2 phalanges and the fingers have 3 for both humans and ferrets. The thumb in the ferret is like a finger. Just imagine what a ferret could do with a human thumb....
Leg bones: The femur, tibia and fibula are very similar. The ankle bones are slightly different to improve jumping ability. The foot bones are like the hand bones. The pelvis (composed of 2 os coxae and 1 sacrum) is similar to other carnivores; human pelvis are twisted because of our upright posture, and widened to allow our infant's hypertrophied cranium to pass through (Ouch is right). Oh yes, the male ferret has a bacula (os penis) and the female an os clitoris. Humans don't. Figure it out.
Back and Chest bones are very similar to all other carnivores, except the length of the vertebrae. Human vertebral columns are modified for upright posture, and the neck bones are much shorter. Both ferrets and humans have 7 cervical vertebrae (as well as giraffes), so the length of the neck is related to the length of each vertebrae. Ferrets have 15 thoracic vertebrae, so they have 30 ribs (sometimes only 14T with 28 ribs); humans have 12 T-vertebrae. Their sternum is made up of 8 bones, humans usually 1 or 2. Ferrets have 5 or 6 lumbar vertebrae, humans 5. Ferrets have 3 sacral vertebrae, humans 5. Oh, humans don't have a long tail you big ape; we have 3-4 caudal vertebrae, ferrets about 18.
Head bones: In humans, there is a single hyoid bone and in ferrets have 9. The ferret's jaws do not fuse in the centre like a human, and their upper incisors are rooted in a premaxillary bone (2 total) not found in humans. The rest of the skull is about the same except for a couple of bones that fuse in humans. The place where the jaw articulates with the skull is different, and the ferret has a bony covering over the middle ear called the auditory bulla which protects the ear and improves hearing.
Now there are quite literally thousands of ways the ferret skeleton can be told from the human (besides size), but for the most part, they are more alike than different. This is true of most mammals (excluding those that fly or swim) and sometimes you can get fooled. The bear paws look close enough like human hands that even police have been fooled. When I was in Ca Ca Land, the police asked me to help determine the sex and ethnic background of a fresh human femur. It was from a black bear.
Now the quiz. Knowing what I said were the average number of human bones, and hearing the differences as described, how many bones does the average adult ferret have?