Why do deer shed their antlers? Could you just walk up to a deer and take their antler off without hurting them?
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They only need them during breeding season so otherwise they’re just heavy and a hindrance so they just naturally sort of fall off.
Image a tire swing on a tree that kids play with in summer. As winter approaches, they know they won’t be using it as much, so it makes more sense to take it down and put it away. The same is true for deer antlers. Antlers require a lot of nutrition to grow, and after a period of growth in the spring and summer, their need for nutrition decreases as winter approaches. Deer are very conscious of their energy expenditure in the winter months, so shedding their large antlers can save them energy and help them survive the cold season.
I’ll add there was a biological theory I was taught back when called the “Spatula Theory” which says sometimes deliberately detrimental features can be selected for via sexual attraction.
For example in this sense, let’s allow that having the biggest, strongest antlers is correlated to being a really fit organism and getting the opportunity to reproduce more effectively. Let’s allow that part of it is that female deer are *choosing* mates based on having big, impressive antlers.
Now growing antlers is nutritionally demanding so there is clearly a benefit to *not* losing them, to just growing the biggest most impressive set once and being done with it. BUT what if a male deer loses their antlers and STILL grows a new totally impressive set every spring. On order to do so it would imply that deer is so well fit, so well adapted and strong and hardy that it’s basically showing off every spring. Female deer will chose that male to mate with because he’s basically flexing on all the other deer. That’s the spatula theory, the inheritance of undesirable traits under sexual selection to highlight the “most fit” individuals.
Another example could be birds with wildly brilliant plumage that is like the opposite of camouflage. If a bird can survive and try and mate while clearly being an easy target for all predators, it *must* be a prime example of a super hardy organism.
Antlers are some of the weirdest biological structures.
Anyway, antlers grow every year. They are covered in velvet, a fleshy tissue that encases the growing bone of the antlers. The velvet is shed, leaving dead, exposed bone. That’s the final antler that deer use to spar with each other. After the mating season is over, these antlers are shed.
So why shed antlers? Well, young deer can’t grow very impressive antlers compared to big, mature deer. But antlers are dead tissue, they can’t grow anymore after they are grown. If deer didn’t shed their first antlers, they’d be stuck with their original small antlers. By shedding them, they can regrow bigger and better ones the next season.
Now all this is _super weird_. Normal horns are live bone covered with hard keratin. They constantly grow, because they are living tissue, not dead, exposed bone. There’s no need to shed them because they keep growing.
How did deer get their bizarre headgrowths? I don’t think that is actually well understood yet.
They grow in the spring and are surrounded by velvet (vascular tissue) once the antlers are done growing the velvet dies and falls off this happens in later summer. Once the velvet is gone the antlers are “dead” they are just solid bone sticking out of their head you could saw them off and not inflict any pain. They are however solidly connected to their scull so you can’t just take them off, but in the early spring long after they are no longer useful for sparing for mates and what not the connection to their scull begins to weaken to the point eventually they just fall off. In most cases they fall off within a few minutes of each other. As to why they do this there are a few advantages, but conserving energy probably isn’t one of them like people have said because they keep them well through winter and don’t fall off until spring when the new antlers start to grow. With deer species their antlers get bigger each year which makes them better at fighting and winning more mates as they get older. Their antlers are also susceptible to breaking during sparing or tree marking so regrowing each year keeps that from being a life altering event and keeps it just a one year set back. Also for their antlers to grow their whole lives and never fall off they would need some way to have blood supply and bones just don’t work that way they. In order to grow they need to be surrounded by tissue with blood flow. Animals that have permanent horns are not bone they are actually more like fingernails or claws they made of keratin and grow from a follicle.
So bottom line, they are bone, they grow surrounded by tissue, that tissue needs to be gone for the antlers to be useful in the fall for fighting so it dies and falls off. They use the antlers fight for mates. The antlers then fall off to make way for a bigger pair of antlers the next year so they win more fights. If you were to find a deer right at the right time in the spring yes you could pull them off but any other time they are connected very solidly to the skull.
Evolutionarily speaking and old deer equals a fit smart deer who has done a great job finding food and avoiding predators. Old deer have the biggest antlers so they win the most fights and mate the most. Bata bing bata boom.
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