From the nearby thread about animals having a sense of humor:
Commonly, animals in captivity tend to be kind of stupid about swallowing things they shouldn’t – probably more so than street-smart animals in the wild. Fubaya is probably correct that a wild animal would probably have better sense about what to eat.
Dolphins have extremely limited digestive systems. They can digest fish (including the skin, scales, and bones). But they can’t digest plant material (cellulose in particular) at all – not even slightly. Tiny pieces might pass through. Larger amounts might get stuck in one of the dolphin’s stomachs (there are two, IIRC) forever, or until the stuff just rots there.
But on the other hand, you have to trick them to swallow their pills. Captive dolphins are commonly fed specially formulated vitamin supplements that somebody somewhere decided they probably need. We stuck them inside a fish and fed that to the dolphin. Our dolphins didn’t like eating those fish. They could always tell which fish had the pills in them. So we shoveled a bunch of fish into the dolphin, one at a time, rapid-pace, with the pill fish in the midst of them. As long as there was another fish coming immediately following the pill fish, the dolphin would gulp it down so as to be ready to eat the next fish.
Dolphins are very imitative, and tend to copy any behavior they observe as best they can. (The same post quotes above also tells of one dolphin learning to twirl a frisbee on its snout just from watching the other. Karen Pryor tells of a dolphin that accidentally got brought in (instead of a different dolphin) to perform a show that it was never trained for. That dolphin managed to perform the whole show kinda-sorta-passably-well, just from having watched the other dolphin do it every day.
There is a story out there of a dolphin who lived in a tank with a manatee. The manatee ate sea grass. The dolphin got sick after a while and died. Upon necropsy (autopsy for animals), they found its stomach was packed solid full of undigested sea grass. The dolphin had gotten into the habit of eating the manatee’s grass. Oops.
Yes, AaronX dolphins have teeth. Bottlenosed dolphins have 88 of them! Every one is a sharp pointed canine-type tooth, like little icepicks. There are no molars, bicuspids, or incisors. Captive dolphins, once tamed, tend to be friendly playful non-agressive critters. Usually. But they are amazingly strong-minded. (I think they must have some dachshunds in their ancestry.) If you piss them off, they sometimes chomp you. For example, it was forbidden (by the dolphins) to try to pet them when they thought you should be busy thawing fish for them. They’d chomp you for that!
One game I played with them was pulling them around through the water. They always like that. I grab them by the tail and pull them backward a ways. (They have very tough tails, so this isn’t going to hurt them.) Then I’d grab them by the snout and pull them forward. They got in the habit of grabbing my arm or hand (with all 88 teeth!) and hanging on while I pulled them around. They were always very gentle about it. I’ve met a few other dolphins like that too. But I’ve also met a few dolphins who weren’t gentle like that.
Dolphins don’t really chomp down when they bite you. Rather, they slash with a sideways movement of the head. This leaves a bunch of long parallel teeth marks in you, which might be deep enough to draw blood. Even just playing (as described above), their teeth are still sharp and leave scratches.
One day, one of the dolphins took a real nasty chomp out of one of our volunteer assistants, for no obvious reason. She had several serious deep parallel slashed on her arm – enough to go to the hospital and have them all stitched up. Nobody had any idea what might have suddenly brought that on. Dolphins have minds of their own. The story came back that the hospital staff was fascinated, having never seen dolphin bites before. They had a staff artist come in to draw a detailed illustration of what an arm full of dolphin bites looks like.