Result is mostly toward smaller and shorter-lived individuals-
Human fishing and hunting accelerating evolution of species. Fishing and hunting by humans is accelerating the speed of evolution in some species as it removes whole generations of large adults who would otherwise reproduce. By Richard Alleyne, Science Correspondent. UK Telegraph.
Assuming that the prey does not become extinct, this finding is just what you’d predict when faced with heavy hunting, harvest, or whatever you call it. Heavy predation speeds up evolution, and the direction of the evolution is in the direction that makes the prey less desirable (such as smaller). Therefore, more of the prey survive by evolving into something not so sought after by humans.
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All the reason for more national parks and hands-off areas to wildlife management. There are virtually none of those in the east and I (and others) have been blasted for suggesting them….
Ralph – I emailed you the following article from Newsweek on the same subject but by a different author last week. Here’s the link, for those interested.
http://www.newsweek.com/id/177709
This was the most interesting aspect of the newsweek article to me:
“So what if fish or kangaroos are smaller? If being smaller is safer, this might be a successful adaptation for a hunted species. After all, ” ‘fitness’ is relative and transitory,” says Columbia University biologist Don Melnick, meaning that Darwinian natural selection has nothing to do with what’s good or bad, or the way things should be.”
Of course it would be ironic if hunting pressure forced elk and deer to have smaller (or no) antlers – kind of takes the trophy out of trophy hunting. It is another story altogether, however, if that pressure caused the species’ fitness for survival to be in jeopardy, which, of course, is happening with certain species.
There was an interesting article in Nature about 3-5 years ago that looked at bighorn’s in the Calgary area. They examined the size of the animal, and the horn size and complexity of animals currently alive versus those analyzed 50 years ago. They found that the same age of animal now had reduced size and reduced horn complexity compared to the earlier animals. Their conclusion was that years and years of hunters taking the most impressive animals allowed the smaller. scrawnier animals to survive and breed. Probably cutting back on predation also helped the less fit males to survive as well. So by the combined effect of trophy hunting and reduced predation, a less fit bighorn was being actively selected for.
jdubya – to play the devil’s advocate, less fit for what? Certainly, the bighorns that were being selected (the ones that survive/were not killed) as a result of the increased hunting/predation were less fit as trophy game animals and therefor potentially more fit to survive given the current environmental pressures (I am including human hunting), so selection was working in their favor on that end.
Is it safe to assume in all circumstances that because the traits we equate with fitness make them less fit as a species? We must be careful when we make blanket value judgments about species fitness, in these instances. It is an interesting discussion, though. I’m certainly not claiming that I know the answer!
I think in certain cases this could be true, espicially with unregulated hunting. But on the flip side, prey species that are properly managed have been getting bigger or atleast maintaining there genetic fitness. Look at the number of B&C Elk, Mule deer, and White Tail deer entered the last few years, the threshold has been raised yet the entries still come in. Most of the “data” cited delt more with poachers than regulated hunting.
Newsweek shoud do an article on how people are becoming less genetically fit due to lack of predation and natural selection.
If only such an evolutionary process were to happen to humans, like a selected for trait that included intellect and kindness… Maybe that’s what were headed for eventually, especially after all the wars, synthetic drugs and fast food that surely must be affecting us somehow. One odd factor is that the more intellectual and educated the persons, especially women (studies show), the less likely they are to reproduce or do so in large quantities (number of children born to each individual). Of course, less children per bearer, the better each is able to survive… hmmm.
Most people are discussing hunting, where there are some good examples (and after Ryan, some not so clear). However, I think this effect is being seen in its most pronounced form in the commercial fisheries of the high seas.
Ralph – yes, and I can’t remember if it was one of these articles or another that said that the logic of keeping the big fish and throwing back the small ones may not be the best, if the concept that the bigger fish are the best reproducers is true. Of course the fishing industry really needs to address not only overfishing in general by by-catch in particular.
I agree with Ralph that the most serious impacts have been in fisheries. That said, sport fishing reg’s in some cases are the most enlightened with the biggest and the smallest fish protected and only those living in the middle of the bell curve allowed for capture.
On the ungulate side, managing hunting relative to the rut can ensure that big antlered males pass on their DNA prior to being hunted. Death is not a genetic selector, breeding is. Similarly, that is why humans begin suffer so many ugly diseases and cancers after about age 35, nature could care less about how and when we die after we have bred and made our kids self sufficient so there has been no selection process to rid us of these ailments.
Perhaps there is a selection process still in play on the human level. Just look at all the birth defects we purport to be engaging a “war” on these days and the number of children suffering by way of these defects that we are supposedly “saving” them from by way of medical intervention, sort of.
And then the supposed “right” to bear children regardless of the genetic “fitness” of the parents, including artificial insemination, sperm banks and such – all to satisfy some “urge” to reproduce for those who lack the capacity to do so naturally.
Nature gets in the way of human satisfaction. How odd to have that as the obstacle instead of accepting nature as the deterrent to overpopulation regardless of genetic health. Humans want to control nature and its dominant features of control, whether it’s pretty or not, we just can’t accept it so we spend billions on insisting that humans are the great controlling feature in the biosphere… and we are losing the “game” so to speak but are in serious denial of that overwhelming truth of it. Just my opinion, but please understand that I am an anthropologist, and that’s my take-home message on the fate of the human population and its longevity and selected-for fitness for survival. When all the synthetic “propping up” of the genetic fitness loses its affect, the “sorting out” will become obvious. Just like all the other flora and fauna of the biosphere. We are not immune to the natural processes, we may be able to temporarily fake it but it will come home to roost eventually.
Speaking only of game animals in the western US…it’s very difficult, if not impossible, to say that there’s been any sort of selection due to human hunting and I would be highly skeptical of anyone making that claim. There were almost no animals at all 100 years ago, and that reduction of genetic variability has to have had a significant impact, much like the genetic bottleneck of the YNP grizzlies.
Anecdotally, habitat has a huge effect on body mass and antler size year to year. You can quickly grow some pretty large game animals if you put them on great ground and protect them from unregulated hunting. Given this variable, it would be tough to measure incremental changes in body size over such a short period of time – even several generations of elk, deer or whatever.
Tom Page,
Good point, evolution of any species takes a long time and localized environment is a major factor. Any year-to-year variance is not a good indicator of evolutionary change. There would have to be a sustained, over a pretty good stretch of time, consistency of the traits manifest for several years for this to be really “proven”, so to speak.
Unrelated except for the evolution part. My daughter just earned her Phd doing this research in Russia and elsewhere.
http://news.nationalgeographic.com/news/2008/10/081027-vampire-moth-evolution-halloween-missions.html
Wow, unrelated or not, that’s really interesting. I wonder how long this transition took for this specific variant to emerge. Insects may or may not take a long time, from human perspective, to make environmental adaptations of that sort.
Everyone has heard of Darwin’s finches in the Galapagos Islands.
When we were there about 5 years ago, we learned that recently a vampire finch had evolved.
“I wonder how long this transition took for this specific variant to emerge. ”
I think that’s the focus of her post-doc research.
Found it.
Letters to Nature
Nature 426, 655-658 (11 December 2003) | doi:10.1038/nature02177; Received 11 August 2003; Accepted 17 October 2003
Undesirable evolutionary consequences of trophy hunting
David W. Coltman1, Paul O’Donoghue1, Jon T. Jorgenson2, John T. Hogg3, Curtis Strobeck4 and Marco Festa-Bianchet5
1. Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK
2. Alberta Department of Sustainable Development, Fish and Wildlife Division, Box 1059, Canmore, Alberta T0L 0M0, Canada
3. Montana Conservation Science Institute, Missoula, Montana 59803, USA
4. Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
5. Département de biologie, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada
Correspondence to: David W. Coltman1 Email: d.coltman@sheffield.ac.uk
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Phenotype-based selective harvests, including trophy hunting, can have important implications for sustainable wildlife management if they target heritable traits1, 2, 3. Here we show that in an evolutionary response to sport hunting of bighorn trophy rams (Ovis canadensis) body weight and horn size have declined significantly over time. We used quantitative genetic analyses, based on a partly genetically reconstructed pedigree from a 30-year study of a wild population in which trophy hunting targeted rams with rapidly growing horns4, to explore the evolutionary response to hunter selection on ram weight and horn size. Both traits were highly heritable, and trophy-harvested rams were of significantly higher genetic ‘breeding value’ for weight and horn size than rams that were not harvested. Rams of high breeding value were also shot at an early age, and thus did not achieve high reproductive success5. Declines in mean breeding values for weight and horn size therefore occurred in response to unrestricted trophy hunting, resulting in the production of smaller-horned, lighter rams, and fewer trophies.
timz,
Thanks for sharing that. And Congrats to your daughter.
Thanks Salle, as you can imagine I’m quite proud of her.
I would be too. I don’t have any of my own children but have raised two generations – my siblings and some of their children. One of the siblings and helped with three of their young who have all been through college now. I am most proud of my one and only nephew who went into environmental sciences at U of Hawaii, got a BS. He was the most difficult to deal with in his teen years but made it through the mire after all.
It’s always a good feeling to see someone you love reach goals and achievements like that. ; )
Jdubya – As we don’t have the whole study to look at here, I can only comment on a couple things. First, the oxymoronic phrase “unrestricted trophy hunting” is worth noting. Management programs that aim to produce big antlers/horns always have very strict kill numbers. I would argue that you can’t have “unrestricted trophy hunting” at all. In a species such as sheep, where there is rarely much interaction between bands, and the bands are usually small in number, killing off the larger males with definitely have an impact on heritable traits within that band.
However, sheep (and elk and deer) live all over the west. Many bands live in unhunted areas, and other bands are subject to very conservative kill numbers. Poor management on one band or herd has little impact on the species as a whole, over time. Taking this study and applying it to othe antlered/horned animals across the west is risky at best.
It’s also worth noting that, at certain times of the year, large breeding males have been highly vulnerable to all kinds of predators for millennia, yet there still seem to be big-antlered elk around every fall in places with good management.
Second, it has been documented that sheep involved in transplants show explosive horn/body growth for several years after being introduced (or reintroduced) into new ungrazed habitat. To try and pinpoint the cause of reduced or increased body mass or antler growth is difficult to do with so many variables in place, for species as widespread as sheep, elk and deer.
Now with fish its very true, even on the sportsfishing size.. No one need look further than the kenai and to see the effect of taking nothing but the biggest and baddest fish out of the gene pool. There used to be 40+ 75lb kings entered into the trophy program, the number is now less than 10 a year on average.
http://www.pnas.org/content/early/2009/01/12/0809235106.full.pdf+html
This is a link to the site where you can obtain the report. Unfortunately, one must have a subscription to the Academy to get it. So, if you know any professor types who just may have that membership….WINK!!…there you are.
I realize this report will bring a flurry of “it doesn’t apply out here” stuff from hunters, but read the report, or listen to the Science Friday segment before you reject the application of its principles to trophy animals here.
I mean, really, would it matter all that much if the head on the wall wasn’t the BIGGEST? Or if the fish you caught that was HUGE was put back to keep those genes in the pool, so to speak?