If you look at this python swallowing a springbok, the springbok has horns poking up that the snake has to swallow down. I understand that snakes can stretch a lot, but they’re stretching from the pressure of the animals inside them, and I would think the sharpness of the horns would injure the snake’s insides on the way down.
As a separate but related question, there are other animals which have pretty big horns, the sheer size of which would make them hard to swallow. And in that case, I’m wondering if the snakes have a way of recognnizing that they won’t be able to get them down, or if they just kill them first and find out the hard way.
I can mostly answer the second part: snakes are pretty darn smart about only killing what they can eat. I’m sure the occasional mistake is make, but the average snake would rather wait another week (or month) for an ideal meal than to risk expending a lot of energy, or even getting hurt, on something they might not be able to eat. They do know by sight whether a particular animal is the right size and shape.
My pet snake, for example: I used to buy rats, but he has a very specific mental line regarding rat size that he’ll eat. So now I feed him mice because there’s no risk of mis-judging the size at the store and having him refuse to eat the almost-medium-size rat. I know he’d be physically capable of eating a rat even twice that size… he just doesn’t consider it worth the risk, though.
As they get hungrier, they do get a little more desperate, though. Using my snake as the example again: usually, he does this slow and methodical stalking of each mouse. He’ll spend ten minutes just two inches away from the mouse before he has the perfect moment to strike But if it’s been more than about two months, he abandons most of the subtle and stealthy techniques and just crawls up, coils and strikes. So if a snake were to try eating something that it couldn’t eat, I’d bet the snake had gone a particularly long time without food and decided the risk was worth it.
dracoi pretty much nailed it. Snakes of all sizes are excellent judges of “swallowability”. They rarely risk injury or wasted effort attacking prey of unsuitable size. And their esophagus and stomach is made of very tough tissue since even prey lacking horns or antlers may have sharp beaks, teeth, claws, or hooves. Prey is preferentially swallowed head first so that projections like limbs and antlers will be folded down into the least problematic geometry.
ISTM that there’s a big difference between sizing up the overall size of a prey animal and figuring out that while the prey is small enough the shape of the horns and the angle they’d be at when being swallowed would make it difficult for them.
I think prey is swallowed head first because the nose is a relatively small part that can fit in easily, and the snake’s mouth and body are gradually forced to expand by the gradually increasing size of the prey body being forced in.
But it’s true that limbs will get folded down (and beaks tend to be in the center and not pressing into the snakes interior walls). That’s exactly why horns should give snakes a much harder time. Because they are frequently sticking out at right angles to the head and neck, and are fixed in place and can’t be folded down.
Horns only stick up when the animal’s face is more or less perpendicular to the neck. By swallowing the antelope head first, the head and neck will be forcibly extended so that the horns will lie flat.
Picture taking a horned animal’s chin in your hand and lifting it up and out, or check out this picture which shows the general effect.
And I bet they break up into gelatinous goo pretty quickly once the stomach acid hits them.
