Artificial selection in action: African elephants are losing their tusks

Reader John O’Neall called my attention to a new article in The Independent about the continuing slaughter of African elephants for their ivory tusks.  This is a form of artificial selection—the elephants targeted are those with the largest tusks—that has a predictable result given that artificial selection on a trait almost never fails:

An increasing number of African elephants are now born tuskless because poachers have consistently targetted animals with the best ivory over decades, fundamentally altering the gene pool.

In some areas 98 per cent of female elephants now have no tusks, researchers have said, compared to between two and six per cent born tuskless on average in the past.

. . . About 144,000 elephants were killed between 2007 and 2014, leaving the species at risk of extinction in some areas. Meanwhile those African elephant populations that do survive could become virtually tuskless, like their Asian cousins, researchers have warned.

Joyce Poole is head of the charity Elephant Voices and has been tracking developments in the species for more than 30 years. She told The Times she had seen a direct correlation between the intensity of poaching and the percentage of females born without tusks in some of the herds she monitored.

In Gorongosa National Park in Mozambique, 90 per cent of elephants were slaughtered between 1977 and 1992, during the country’s civil war. Dr Poole said that because poachers disproportionately targetted tusked animals, almost half the females over 35 years of age have no tusks, and although poaching is now under control and the population is recovering well, they are passing the tuskless gene down to their daughters: 30 per cent of female elephants born since the end of the war also do not have tusks.

You can read a longer and more scientific article about this at the African Wildlife Foundation. When I read about a “tuskless gene” in the bit above, I was dubious, for such selection will work regardless of its genetic basis, and traits like tusk size are usually influenced by many genes of smaller effect. But it turns out that, according to Poole, there is such a gene:

“Elephants carry a sex-linked gene for tusklessness, so in most populations there are always some tuskless elephants,” says Poole. “Because males require tusks for fighting, tusklessness has been selected against in males and very few males are tuskless. For African elephants, tuskless males have a much harder time breeding and do not pass on their genes as often as tusked males.”

I don’t know much about that gene, but it would seem to be recessive, so that tuskless males will always pass on the gene to their daughters, but not their sons (the gene is on the X, not the Y). Tuskless females would have to carry two copies of the recessive gene, and all their sons would be tuskless. But regardless of the genetics, selective poaching of elephants with bigger tusks will cause tusklessness to spread in the population.

tuskless-elephant-ngorongoro-crater-tanzania-michael-hutchins-l-www-worldsafaris-com_

An adult female elephant without tusks, perhaps homozygous for the “tuskless” gene. Source.

You might think that this is fine: that once all the elephants are virtually tuskless, the poaching will stop, for elephants are killed only for their ivory. But it’s not that simple, for tusks are there for a reason: they’re used for self-defense, for digging, and, perhaps most important, females prefer to mate with males having larger tusks. While tuskless elephants may survive without their armaments, a strong female preference for mating with tusked males might mean that such populations simply won’t mate, and that means extinction.

This is not the only case in which artificial selection through hunting has changed a species: many edible fish, for example, have evolved reduced body size because fisherman not only go after the big ones, leaving the smaller ones to breed, but overfishing imposes selection on fish to breed when younger and smaller (those fish with genes allowing them to breed when younger are more likely to leave their genes to the next generation).

What we have, then, is another example of the efficacy of artificial selection, something that we’ve known for decades. (In fact, I know of only three laboratory selection experiments that have failed to change a population, and two of those are mine.) And the effect is predictable. The solution is not to cut the tusks off living elephants to prevent their slaughter, or to let elephants evolve tusklessness, which could lead to their extinction.) The solution is to stop the ivory trade. Steps have been taken to do this, but so long as ivory is coveted in countries like China, driving the price of tusks to stratospheric levels (a pound of ivory can fetch $1500 on the black market; a huge amount given the weight of tusks), the problem will persist, and we’ll see horrible scenes like this:

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Since the tusks extend into the head, poachers have to partially decapitate the elephant.

 

34 Comments

  1. Posted November 27, 2016 at 1:05 pm | Permalink

    Bruce Weir has published on the poaching topic (use of forensic gene tics to identify the poaching hotspots:

    https://www.ncbi.nlm.nih.gov/m/pubmed/26089357/

  2. Posted November 27, 2016 at 1:07 pm | Permalink

    I’m sure Ted Nugent will sign a petition, but not for the sake of the elephants.

    The ubiquity of evil is thoroughly depressing.

  3. Randall Schenck
    Posted November 27, 2016 at 1:13 pm | Permalink

    Could we call this evil – unnatural selection.

    • Diane G.
      Posted November 28, 2016 at 12:42 am | Permalink

      I dunno…it seems pretty natural to our species…

    • peepuk
      Posted November 28, 2016 at 10:53 am | Permalink

      “evil”

      These elephants weren’t killed for no reason (wikipedia):

      “By the mid-19th century, elephants were being slaughtered for their ivory at an alarming rate, just to keep up with the demand for high-end billiard balls – no more than eight balls could be made from a single elephant’s tusks”.

      Now, it seems, after all these years, natural selection has found a way for elephants to fight back a bit so humans lose interest in these animals.

      Isn’t that wonderful?

  4. Mark Sturtevant
    Posted November 27, 2016 at 1:19 pm | Permalink

    It would be helpful if the Eastern countries that value ivory would please just stop, but that will be a long time coming. As several of them grow in affluence, China among them, the poaching problem will only get worse before it ever gets better.

    • Heather Hastie
      Posted November 28, 2016 at 1:14 pm | Permalink

      Also, these days most of the poaching is being done by both Christian and Islamist terrorist groups to fund their own brand of evil. That’s the reason the poaching has increased so much in recent years.

      • jeremy pereira
        Posted November 29, 2016 at 6:58 am | Permalink

        But they wouldn’t do it if there wasn’t a demand.

  5. Posted November 27, 2016 at 1:31 pm | Permalink

    Unfortunately, the Chinese are not the only guilty ones. Religious object of ivory are still highly prized, in spite of the Pope’s recent push for stopping ivory trafficking.

    • gravelinspector-Aidan
      Posted November 27, 2016 at 7:30 pm | Permalink

      True points, however at least in the UK there have been strict regulations concerning movement and ownership in ivory objects for some time now (2+ decades?). When the legislation was introduced, people had a “window of grace” to register existing “historical” artefacts … after which they could not be sold, and without the appropriate certificates became effectively impossible to sell (from an estate), move (particularly by air) or own (without raising an investigation if their existence comes to light).
      I caught 10 minutes of an “antiques” programme last week about this, and the regulations reminded me in strictness of those governing the ownership of “historical” bird egg collections – which can still retain genuine scientific value. Dad had to deal with getting a literal “attic find” of a well-curated amateur egg collection into the BMNH a few years back, and it took about 4 years to do under the threat of the collection being seized and destroyed by the police. Quite a stressful time.
      To be honest, since sex isn’t much involved, I suspect that the western churches will be pretty compliant to this. It’s not “worth the candle” of getting around.

  6. Bruce Grant
    Posted November 27, 2016 at 1:40 pm | Permalink

    I quibble about terminology. Artificial selection is not only imposed by humans, it is goal-directed, as in selecting FOR faster race horses, or FOR higher yield corn. In the case of the elephants it is true that human predators are the agents of selection, but they did not have the goal of selecting FOR tuskless elephants. Despite direct human involvement, the outcome is really an example of mindless natural selection.

    • Gregory Kusnick
      Posted November 27, 2016 at 6:07 pm | Permalink

      I agree. If unintended consequences count as artificial selection, then all predators (not just humans) are guilty of it.

    • W.Benson
      Posted November 27, 2016 at 7:51 pm | Permalink

      Anthropic natural selection.

    • peepuk
      Posted November 28, 2016 at 10:55 am | Permalink

      Fully agree.

  7. Posted November 27, 2016 at 1:57 pm | Permalink

    What a horrifying and sad picture.

    • Diane G.
      Posted November 28, 2016 at 12:45 am | Permalink

      Indeed! Now that could merit a trigger warning.

  8. Posted November 27, 2016 at 2:24 pm | Permalink

    Selection can happen quickly. And to think, when I was a kid, I got my mom an ivory elephant because I knew that she liked elephants. In this case, education made me stop.

  9. Mark R.
    Posted November 27, 2016 at 2:35 pm | Permalink

    The earth would be a lot healthier without the naked ape.

  10. nicky
    Posted November 27, 2016 at 3:37 pm | Permalink

    I seem to remember a graph of declining task size in Ugandan elephants from the thirties tomfifties (cancan’t remember exactly, but there was a wobble during WWII). I even think it was in one of Dawkins books.
    I also remember a pair of giant tusks in the
    Museum for Central Africa in Tervuren, near Brussels, as a child. Tgigantic absolutely gigantic, with a (estimated from memory) widest diameter of about 30cm and well over 2 m long. You don’t see them like that abymore.
    I think that to cut the demand -just like the demand for rhino-horn) will be exceedingly difficult, if not impossible.
    I can think of 2 possible (?) Solutions:
    1 – If ivory is so expensive, might it not be easier to have a captive breeding programme artificially selecting for giant tusks? Selling them in in a market outcompeting the illegal trade? I know such a programme would be fraught with difficulty, both practical and theoretical and the idea might not be really viable. Still something to consider, methinks. Btw, do sawn-off tusks grow back?
    2 – Even better: can ivory not be grown artificially ‘in the lab’ with a quality that is not readily distinguishable from the real thing? If so, the market can be flooded and would make poaching unprofitable.
    (The salvation of the pearl oyster reminds us of both potential solutions here)

    • nicky
      Posted November 27, 2016 at 3:48 pm | Permalink

      Sorry for all the typos, but I hit the “post comment” button before ‘proof-reading’. I hppe it is still intelligible.

    • gravelinspector-Aidan
      Posted November 27, 2016 at 7:46 pm | Permalink

      Both of these ideas have the problem of allowing the existence of a significant market in “legal” ivory to exist, and experience is strongly that a legal market will assist an illegal market because all you need to do to legitimise an item or a shipment is forge some paperwork and pay someone to not notice that it’s forged. The payment can be as low as “do you see this picture of your child at school this morning?” Un-nice people.
      Up thread I mention legitimising a bird-egg collection outside the “window of grace” for such things. It wasn’t my problem (Dad’s problem), but I heard far more than I wanted to about the gory details over the 4 or so years the process took. The process was long, convoluted and difficult precisely to make it really really hard to do, precisely to destroy any residual market in such things.
      The market is the problem. Why is there a red laser-T on my chest?

    • Brendan Moyle
      Posted November 27, 2016 at 9:10 pm | Permalink

      Natural mortality produces about 100 tons a year, not all of which is ever found. But its still a significant amount. There’s a reason many African range states have stockpiles.

      I believe, but don’t quote me on the exact figures, that around 2000 elephants a year are culled in HAC, often belligerent males.

      In trade policy terms however, The CITES ban that came into effect in 1990, and the moratorium that followed the 2008 one-off sale, has made it difficult to pursue a legal trade option.

  11. cherrybombsim
    Posted November 27, 2016 at 4:32 pm | Permalink

    Hmmm, if tusklessness is caused by a recessive gene on the X, then you would expect more males to be affected than females. I think I’d go with your first instinct of it being a polygenic trait.

  12. Posted November 27, 2016 at 5:22 pm | Permalink

    There is a petition to stop the domestic ivory market in the UK. I’ve signed it.

    https://petition.parliament.uk/petitions/165905

    • gravelinspector-Aidan
      Posted November 27, 2016 at 8:01 pm | Permalink

      Good start. Step 2 : next time you are at a car boot sale or second-hand shop (unlikely at an auction sale) and you see an item that may be ivory, call the police. Kick up a stink. Get uniforms to the shop. I think you’d probably need to ask for the “art crimes” unit – that should get you bumped up the food chain to the point that “too many people have been called for this to not be responded to” takes effect.
      As I said up thread, the market is the enemy. If you make every possible small-scale dealer think “that looks like ivory, I’d better not touch it” then you leave only the professional dealer in the game.
      My inner magpie pains to say it, but I’d rather see a nice but unimportant piece of Victorian ivory carving go onto the bonfire than the ivory trade survive. I know enough to know that I couldn’t tell an important piece from an unimportant piece. But I’m perfectly happy to be the “philistine at the gate” who scares those who do know the difference into going through the (long, difficult, involved) process of getting important pieces through the registration process.
      Damn. As Dad’s executor, I’d better make sure that he goes through that process with their house contents (I didn’t get my magpie genes from him – he’s still got his.) before I have to do it.

      • nicky
        Posted November 28, 2016 at 10:26 pm | Permalink

        That might work in the UK, but virtually all ivory is exported to the far east … (and rhinohorn even more so).
        In the West we should better fight the exotic reef-fish trade, often ‘harvested’ using cyanide….

  13. ThyroidPlanet
    Posted November 27, 2016 at 6:09 pm | Permalink

    Sub

  14. gravelinspector-Aidan
    Posted November 27, 2016 at 8:07 pm | Permalink

    Sometimes my inner sadist wonders about a genetic-engineered virus which transmits human-to-human and which would react to ivory (topical contact, or even more if ingested as a powder) by rendering the contacted person green-skinned, sterile, or both.
    Wohlbachia can do similar things, so it’s probably not impossible. Harder to do the “topical contact” than the “ingest powder” thing.

  15. Brendan Moyle
    Posted November 27, 2016 at 8:29 pm | Permalink

    As someone who has researched the legal and illegal markets in China for several years, a few comments are warranted.

    First, I’m not sure the generational length nor the sample range mentioned in these articles, suffice to be confident selection is fast enough, or extensive enough, to end poaching. I note that Asian elephants (Elephas maximus) also have tuskless females and their populations have also declined.

    The dominant characteristic of the illegal trade since 2008, has been the surge in very large shipments of raw tusks (1 ton or more). The illegal traffic in carvings remains a much smaller, and stable element of the trade. It is this surge in raw ivory that has flipped poaching levels to unsustainable.

    This increase in demand for raw ivory (not carved), is linked to financial variables (it’s sensitive to global interest rates), a decrease in stability in many African range states (Central African range states are the worst hit, with poaching rates double elsewhere), and post-GFC, a massive drop in shipping container costs- the modus operandi for criminal organisations. Their costs have fallen.

    Rather than affluence leading to carvings being coveted, investors seem to be treating *raw* ivory like gold. An investment good. If they’d put their money into the Bank or Chinese stock exchanges since 2008, the returns were less than inflation. Ivory has tended to go up in value. They’re not oblivious to this fact. In fact, they’re quite astute investors. We estimate that roughly 200 tons of ivory pa have been smuggled from African range states. The legal market in China uses around 4 tons of ivory per year. The illegal market (which has its own stores and factories) uses roughly double. The evidence suggests most of the ivory is being stored by speculators (cf UNODC report from earlier this year). It is possibly unhelpful to keep overlooking this point.

    As an aside, in terms of the quoted illegal prices, there’s a lot of uncertainty around these above. Black market prices are often inflated in reports. Ivory comes in different grades (4 according to Chinese) and different sizes, making it a very heterogeneous product. You really have to know exactly where in the supply chain the ivory is caught, the year, the quantities and the grades.

    • nicky
      Posted November 28, 2016 at 10:44 pm | Permalink

      So the best tactic would be a drop in value. Flooding the market with artificially grown, but real ivory, for example (if that were possible, some research project?)

  16. Posted November 28, 2016 at 12:36 pm | Permalink

    “I know of only three laboratory selection experiments that have failed to change a population, and two of those are mine.”

    I know you do not like readers to tell you what to blog about, but I’d enjoy a post about this, and I am sure so will many others. I vaguely remember having read somewhere (maybe in Mayr) about a failure to select fruit flies with one-sided traits.

  17. Posted November 29, 2016 at 11:42 am | Permalink

    Another way to help stop this is to work (however one does this – fairer trade, etc.) so that local people do not feel as tempted to work in this horrible business. MacGyver (!) got this right – they point out that the trafficers and the buyers are the problem – the locals are often poor trying to make a living. This is not always so, but it is true that the closer one gets, generally the more “local” the earnings are, etc.

    (MacGyver did an episode, “Black Rhino”, about another wasteful, superstitious practice with another large mammal. Trigger warning on *that*, even though of course it is faked for the fiction.)


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