Trunks!

Hey Li!

I have so many questions about elephant trunks!!??

• How do they move?
• What are they made of?
• How did they evolve?

Through watching some videos and readings I've begun to get a better sense of them, although right now my understanding is still pretty superficial.

So, first of all, elephant trunks are made mostly of muscle and connective tissue. In African elephants, there are over 150,000 muscles that make them up. These muslces run up and down, side to side, and at an angle to the central nostrals running through the trunk. I've been thinking of trunks kind of like water babies (did you ever play with those as a kid?). If you squeeze them in one place, because their volume remains constant, they move in another place.

With all of their muscles and innervation, they can move in tons of different ways. And the way they move is kind of like our tongues or a squid's/octopus's arm. When certain muscles contract and other muscles provide some resistance they can bend in different directions! For instance if a muscle running the length of the trunk contracts and some of the muscles on the other side provide some resistance, the trunk will bend towards the side of the contracting muscle. Or if the muscles going around the trunk contract that the trunk will get narrower and longer.

It's also interesting to think about how sensitive their trunks are. It's like the tip of our fingers or our lips, although it doesn't seem that they have the same kinds of pressure sensors that we have in the tips of our most sensitive fingers. Not only can trunks do incredibly fine muscular things (e.g. take a peanut, break it open, blow off the broken shell) they can also feel very small things. It's funny to think that an animal that's so big has an organ that's so finely attuned and sensitive and can do so many things.

Trunks are used for tons of stuff. They're used to sense sense seismic vibrations in the ground (elephants touch their trunks to the ground in addition to their feet when they freeze and listen to seismic vibrations). When they swim, trunks act as snorkels. Trunks are used to suck up water straight from a watering hole and elephants even have a pouch in the back of their mouth/throat that stores water. They use their trunks to get the water out of that pouch and spray it down their throat when their thirsty. (A fun fact: African elephant's trunks can old up to 10 gallons of water at a time!). Unlike giraffes, when elephants are drinking water from a watering hole, they don't have to put their heads down to get water. Since their heads are so big and heavy, I'm not sure they even could, so trunks maybe even helped elephants to evolve the large brains that they did! Trunks are also used for tactile communication — to touch other elephants and communicate. When elephants are alert and feel in danger, their trunks extend and get stiff and go out. Trunks are also used to grab food and to smell (elephant's noses are very sensitive, perhaps even more sensitive than those of a dog!).

At the end of their trunks, African elephant have two trunk "fingers" instead of one like Asian elephants so it seems that they may be better at manipulating things.

Something else that's pretty cool is that just like human babies don't have as good fine motor skills, neighther do baby elephants. They learn to use their trunks over time like we learn to use our hands. Just watch the baby elephant below vs. the older elephants and what's going on with it's trunk.

Here are some really cool videos I watched:

• A video of a trunk dissection
• video from Science about how trunks are so strong and gentle.
• Here's an article about muscular hydrostats like human tongues and squid arms.

Here's the next letter for you, my dear!