Now that Valentine’s Day is here and spring is upon us, that season when a young man’s fancy turns to love is just around the corner. It seems with all this romance in the air, that we should focus this edition of Conservation Corner on the topic of sexual reproduction. Specifically, let’s talk about mate selection and the surprising way in which trophy hunting is affecting it.
There are millions of species on this planet that reproduce sexually. It takes two to tango as they say, and if an animal is going to have to select a partner, it pays to be picky. There are all kinds of sound scientific principles behind this, but it’s simplest to consider it this way; children tend to take after their parents. This is genetics in a nutshell. If dad is a bigger, stronger specimen, likely his kids will be bigger as well. If mom has unnaturally keen eyesight, there’s a good chance she’ll have eagle-eyed offspring. This is as true for lions and tigers and bears as it is for us humans.
When picking the best dance partner, there are two forces at play. One is natural selection, the other sexual selection. These ideas are closely linked. Natural selection covers the idea of “survival of the fittest” and describes a process by which some genetic traits get weeded out by the trials of life. Those traits that don’t cost an animal its breeding opportunities persist and get passed on to the kids. Sexual selection is a specific mode of natural selection. In the grand scheme of things, being able to survive predators and starvation doesn’t guarantee you a girlfriend. You still have to convince the lady to like you.
To illustrate this idea, let’s talk about the African greater kudu, a beautiful antelope we’re privileged to have here at Safari West. In the wild, kudus face all manner of naturally selective pressures. They have to find food and water in an often arid environment and make it a daily goal not to become someone else’s lunch.
If they survive these naturally selective pressures, kudus also face sexually selective pressures. Like us, kudus have an internal ideal for what they want in a mate. It’s a huge generalization containing a note of truth that women tend to be pickier than men and, in the wild, it’s easy to see why that might be. It costs the male kudu virtually nothing in terms of time or resources to mate with less than ideal females. If the kids he produces with one are less well-equipped to deal with the world, no big deal, he’s likely reproduced with another female anyway. For the boys, it’s often more about quantity than quality.
Not so for the female kudu. She faces an entirely different set of pressures. She’s going to have to carry a baby through an 8 to 9 month pregnancy and then nurse and protect it for another half a year at least. If she breeds with a less-than-stellar male and produces a weaker, less well-equipped infant, that can cost her hugely. In her case, being picky is critically important. The factors by which she judges a potential mate are often going to be indicators as to how well-equipped he is to survive naturally selective pressures.
Consider this, a female kudu can’t go out on a date with a male and ask him how many lions he’s outrun or how often he gets sick. She has to make do with outward signals. Is he big and strong? Then he’s a survivor who’s lived long enough to get that way. If he’s healthy he probably has a good immune system. Does he have big, beautiful horns? Then he’s likely to win dominance fights with other males, indicating overall vigor and ability. It’s an elegant system of encoded signals.
Now here’s where we come in. For nearly 200,000 years now, human beings have served as one of the many forces of natural selection. We’ve always been hunters and, just like lions and leopards, we’ve eliminated certain individuals from the gene pool. Historically, our role has been just like that of our companion predators. The kudu attentive enough to notice the approaching lion would likely also be attentive enough to notice the little guy with the spear creeping up on him. We have generally relied on being able to catch the young and vulnerable or the weak and old. We have helped weed out the less desirable traits and made the target species stronger for it. Our removal of the weakest links left the strongest to breed and thrive; fast, strong, and as heavily horned as ever.
Fast forward to the modern era and the situation has changed dramatically for a few key reasons. First, it’s no longer a fair fight. In the evolutionary arms race between hunter and prey, we’ve taken things to an entirely new level. When we invented projectile weapons like spears, bows, and arrows, we changed the game. The kudu had always needed to stay out of a predator’s reach but now they had to learn to stay out of our range as well. Had we settled for bows and arrows for a million years or so, maybe the kudu could have evolved a response, but we didn’t. In a hilariously short period of time, we also invented snares, lures, firearms, camouflage, scopes, and a hundred other technological toys that tip the scales so far in our favor that there’s now nothing we can’t kill.
Alongside this technical prowess, we changed our targets. Now that we can kill any kudu we choose, why settle for the little guy, or the sickly one, or the old female with the scarred hide? Especially when there’s a big, beautiful male with an incredible rack of horns over on that hill? When we stopped relying on killing just any animal to survive, some of us became trophy hunters instead.
Big game and trophy hunters are not all that common. They are a small subset of the global population, but there are seven billion of us and even that small percentage is big enough to make an impact. There are of course concerns about over-hunting. In the past, we have hunted some species completely out of existence. In many places in the world, there are now strong networks of regulations in place to prevent that very thing. Deer hunting is incredibly popular in the United States, but our resident deer population is in no real danger of extinction. No, the effect caused by trophy hunting is something altogether new.
By targeting the best individuals in a species, we are applying a selective pressure that actively opposes that of other predators. The big male kudu with the long spiraling horns has proven he is a capable survivor. His weaker competitors have fallen to the lions or lost battles with him or starved in the dry season. His genes are exactly those that should be passed along to the next generation. And he’s the very animal we’re now looking to harvest.
This has a tremendous impact in the world of sexual selection. The hornless female kudus (or maneless female lions, or smaller-tusked female elephants) are now being courted by the B-team. The younger, weaker males who’d normally never get close to a fertile female are slowly becoming the only options in town. The females are making do, but this amounts to a degradation of the gene pool. The very animals who are more susceptible to lion attack and drought are the very ones contributing to the next generation.
There are several recent studies outlining the effect of this reverse pressure. Removal of the largest male big horn sheep in Alberta Canada seems to have reduced the overall size of the adult animals and caused them to reach sexual maturity faster. The logic here says that younger animals who can successfully breed before they find themselves in the crosshairs, or smaller-horned animals who are being passed over, are increasingly dominating the gene pool.
Likewise, data collected by Mark and Delia Owens in Zambia demonstrate that the incredible demand for elephant tusks has led to a stark increase in tuskless elephants. Historically, tuskless African elephants are genetic oddities accounting for less than 2% of the population. As their large-tusked herd-mates are harvested, these rarities are presented with unprecedented breeding opportunities. As of 1997, tuskless elephants made up 38% of the herd.
Our focus on the best and most idealized animals is fundamentally weakening many species. Millennia of weeding out the poorest genes have crafted these animals into the beautiful, strong survivors they are today. Our novel habit of taking only the best is causing cataclysmic reversals in population trends.
The so-called “unnatural selection” resulting from activities like big game and trophy hunting, is a relatively recent phenomenon. The effects of this type of selection have only come to light in the last century or so. Furthermore, there has already been some evidence indicating that when our pressures abate, the genetics tend to rebound. Not surprisingly, the process of recovery takes longer than the degradation, but recovery is possible.
We are now too many and too powerful to go charging through the world taking whatever we will, blind to the consequences. We are learning that the force of selection we exert is so strong that we’ve begun to take the reins of evolution. The question is what will we do now that we have them? Will we continue to weaken the species we hunt through apathy and ignorance; destabilizing the ecosystems they are a part of and putting them at risk of extinction? Or will we accept this unexpected challenge and learn to manage our practices responsibly?
Luckily, there’s quite a bit we can do to affect change. Our responsibility first and foremost is to make sure that our hunting practices are sustainable. A few changes to current hunting regulations would be a step in the right direction. The specific rules vary by species, but the driving logic is the same: identify the selective pressures we are introducing to the species and work out how to mitigate them. As a general example, this means less emphasis on size-based regulations and more on viability-based regulations. It’s one thing to mandate that a deer can’t be taken until it’s a certain size, but the overall population would be better served by a regulation based on breeding viability. Waiting to take strong males until they are past their breeding prime would make a tremendous difference.
There are numerous steps we can take to address this problem but they will all stem from the same basic truth. The animals walking this planet today are the result of millions upon millions of years of careful selection. If we want them to continue on that route then we need to apply the same diligence in our own selective practices. Our courtship behaviors have driven our own species relentlessly toward bigger brains and better cognition. Now that we’re being made aware of a problem we’ve caused through ignorance, let’s apply our evolutionary bounty toward finding a solution.