steamer

Why is it that deer do not have razor sharp points on their antlers? Deer antlers come to a point, but it is not a very sharp point, in fact it's kind of blunt compared to the horns of many animals. It seems to me that evolution should have favored sharper points on the antler both for defence from predators and for dealing with rivals. Any ideas?

Angrillori

A few thoughts:

#1) Structural limitations? Maybe the structure of antlers just dulls more quickly than others. like how our teeth aren't as sharp as they were when they first grew in.

#2) Since the antlers play a key part in mating rivalry, non-lethality is important. (Remember what doesn't hurt the other guy as much also doesn't hurt you as much when it is used against you.)

#3) Since deer are primarily "escapers" and not "fighters" perhaps antlers with sharper points and edges were more likely to get stuck/tangled whereas smoother, rounded antlers were less likely to "snag"?

#2 would be most important I imagine, but I can see how #1 and #3 could play a part.

Mageth

Some species of deer have sharp points on their antlers; some don't. Remember, Elk, moose (called "elk" in Europe, I believe), whitetail, blacktail, mule deer, red deer, and reindeer/caribou are all species of deer. There are others.

My experience with the ones that do (e.g., whitetail and mule deer) is that their antlers are plenty sharp to inflict major damage.

Hiowever, deer antlers are primarily for "dealing with rivals", and not defense against predators. In many deer species, the females don't grow antlers. Further, most deer shed their antlers in the late winter and regrow a new set for the next mating season (when the males compete for females).

Like many other species, the intent of the "bouts" between males (bucks) is to establish dominance, not to inflict injury. Such bouts are generally more like shoving matches than "swordfights". Thus, sharpness is not essential when two male deer fight (the bucks are not trying to kill, or even injure, each other, but to establish dominance), nor is it essential to impress female deer (does). It's really size, strength and health that are important. Larger, stronger bucks with typically larger antlers tend to win the "bouts", or win by default when the smaller bucks back down, impressed by the size of the larger bucks with their big "racks". Further, the size of the antlers may express to the does the general health of the buck.

steamer

Ah, that's probably it, but how it would get selected out if ever it got selected in?

steamer

I'm not sure that the males aren't trying to kill each other. I think they would if they could and that would certainly establish which one is not going to participate in the gene pool. The way that antlers are grown though seems like it may be a structual issue as opposed to another selector.

Mageth

When deer fight, they generally don't gore each other, though it happens from time to time. Again, note that the intent is not to kill or injure, but to establish dominance. Deer jousts are typically head-to-head shoving matches, not lethal gore-fests.

But, suppose that, in one group of of a species of deer, for some reason sharpness/lethality was selected for, either in the form of the antlers or in the method of fighting (they fought with the intent to injure/kill), or both. In another group, it was not.

The male of the lethal deer would tend to kill each other off at a higher rate, no? And thus, probably, have fewer offspring.

Thus, non-lethality in mating rituals can be a survival advantage for a species, and thus may be (has been) "naturally selected".

steamer

That makes sense. Also answers my other question.

cgordon

I've seen a man gutted, more or less, by a common North American deer, and have heard of other similar events. During mating rituals, the 'dance' is pretty well-established and not lethal. They're a bit like Niven's Puppeteers ... well suited for flight, but also capable of great damage.

Mageth

I am. The intent of fights between male deer is to establish dominance. Once one retires from the fight, it's over.

They could, but they don't. That's the deal. Deer antlers (of those species that have sharp antlers) are sufficiently lethal to inflict serious injury or death on other male deer. But they fight in such a way (shoving matches) to not do injury, but to establish dominance.

Their non-lethal behavior has been selected for. A propensity to kill other members of your own species is not a good "plan" for passing down your genes. Remember, those you kill may share many of the same genes as you.

And, this is important, you may get killed yourself. If a male deer has a "violent" tendency and thus tries to kill an opponent, the opponent (no matter what its tendency) may instead kill it.

Suppose you had a population of deer, where 50% of the male deer "went for the kill". Let's call them the "lethal group." Instead of shoving matches, they tried to kill their opponent. In so doing, their opponent, in self-defense, might instead kill them, no matter what its behavioral tendency was. For simplicity, let's assume, for deer in this group, the chance of surviving or getting killed in a fight against any opponent is 50/50.

Now, the other 50% locked antlers and shoved, and backed down when they figured out they weren't the strongest. Let's call them the "non-lethal" group. For simplicity, let's assume, for deer in this group, the chance of surviving confrontations with each other is 100%. (note that it would be 50% against "lethal" deer).

So, when two males confronted each other, they may both be of the lethal group, or both of the non-lethal group, or one from each.

The deer from the "lethal group" would get killed at a higher rate than the ones from the non-lethal group - no matter from which group their opponent is from. The bucks from the "lethal" group have a 50/50 survival rate, no matter which group their opponent is from.

The bucks from the "non-lethal" group have a 50/50 survival rate in fights against males from the lethal group, and a 100% survival rate against males from the non-lethal group. They survive confrontations with other males more often. And are thus selected for.

The numbers I used are, of course, exemplary. The same priinciple holds, however, if you tweak the numbers up or down. For example, the "non-lethal" bucks would still have an advantage if their survival rate was 75% against members of their own group, and 40% against males from the lethal group.

A tendency to non-lethality in confrontations with members of your other species is a significant survival advantage.

Again, deer antlers (on species that have sharp antlers) are sufficiently sharp to inflict major injury or even to kill. Yet, generally, male deer don't kill each other. Why? Because doing so is not beneficial, and tends to be selected against.

Mageth

Typically, North American deer defend themselves against predators or other threats (e.g., humans) with their hooves more than their antlers, anyway, though their antlers can do serious damage. Their hooves can tear you up as well.