I wanted to try writing more meaty topics, so this is a bit longer and more serious than my other posts…
As a species we have had a pretty big impact on our planet and all who live here with us. Our influence extends to the deepest oceans and the highest mountains. We have even changed our atmosphere. While we label many species, habitats and places as ‘wild’, ‘natural’, ‘native’, or even ‘untouched’, these labels really start to lose their meaning when you consider just how much of our planet has been touched by us.
Yet often we act as if these labels still have genuine meaning. We try to ‘protect nature’ in small packets of land, and then monitor and maintain these islands to ‘keep them natural’. Genetic purity of rare or endangered species is jealously guarded and protected. We get agitated when one species that has benefitted from humans eats, kicks out or breeds with another species that has suffered at our hands.
But wait: why this divide between human and natural anyway? We evolved out of the primeval swamp just like every other bug, plant and animal. While we have found ways to manipulate, control and change our surroundings and fellow earthlings, we are just as much a product of Mother Nature as Bambi and Thumper, surely? We’ve certainly made a mess of the place, but we’re not exactly in a position to put everything back how we found it.
While a part of me would love to see the planet restored to pre-human, or at least pre-industrial condition, this isn’t going to happen. So how far should we go to protect and preserve species and habitats, and is it time for a more pragmatic, realistic form of nature conservation? Species hybridisation is a good place to start in examining the issues: just what is the trouble with mongrels?
The ruddy duck is native to the US but enough captive animals escaped in the UK to form a viable breeding population. So far no problem: we have nothing like the ruddy duck here, the birds posed no threat to UK natives and were generally seen as a welcome addition to the British wildlife scene. But after a while our ruddys started migrating to mainland Europe, where Spain is host to a cousin of the ruddy, the white-headed duck. A duck with problems if ever there was one, the white-headed came close to extinction in the 1970s and is still struggling today. And outrageously, the female white-headeds fell head-over-heels for the male ruddys and produced fertile crossbreed offspring. The Spanish were not amused, and to cut a long story short nearly all the 4000-6000 strong UK ruddy duck population has now been culled.
In the eyes of those who called for the cull, the ruddy duck had committed two crimes: it had arrived in the UK through human – not natural – means, and it had interbred with a duck that we humans consider to be a separate species. While unfortunate for the ruddy, this example throws an interesting light on our relationship with our wild neighbours.
What’s the problem with immigration?
Movement of populations from one place to another is not exactly new. All species – including humans – evolve someplace and then spread out to colonise new places. This colonisation process may or may not be detrimental to the original inhabitants.
In Britain the ice age created a blank sheet from which all our ‘indigenous’ inhabitants started from, trekking or flying across the land bridge between Britain and Europe. The first intake of humans was aggressively added to by Romans, Anglo Saxons, Vikings and Normans. These invaders brought with them animals, plants and birds that had failed to cross the land bridge. Rabbits, fallow deer, edible dormice, rosemary, thyme, walnut and sweet chestnut were all brought to Britain by these invaders.
If we are responsible for moving species from one place to another, does this mean we should feel obliged to ‘put them back’? I think the answer to this should always depend on the situation: have we really screwed up this time (think cane toad and Japanese knotweed), and is it worth the effort anyway (think grey squirrel and sycamore)? But really, I’d like to see conservationists get a little less hung up about how this species got to that place. If it’s not being too much of a nuisance let it be.
With hybrids, where the parents can breed naturally but are only doing so because we introduced them, we get upset because some animals or plants have mixed up their genes with our help. But why should this be a problem? After all, no one gets harmed as a result of the liaison.
Species purity: what’s the fuss all about?
What is a species anyway? In lay terms, if they can produce viable offspring and choose to do so, they’re the same species or sub-species. If the ruddys were allowed to mate with the white-headed ducks, the gene pool would expand, but would the white-headed duck become extinct? And would this be bad for the Spanish population of stiff-tailed ducks?
I think our problem with hybrids stems from our obsession with pedigrees. We love creating and refining breeds. Plant breeders are a lot less fussy about pedigree – they care about their cultivars having the desired characteristics, but this is often achieved through cross-breeding. But in animals it’s a different story. A pedigree dog can be worth so many thousands of pounds. But if the parents don’t have the right paperwork, in the breeding and showing world it is worth nothing.
Yet actually genetic diversity is a good thing. Pedigree animals and rare breeds can have huge problems – deformities, physical weaknesses, behavioural problems, and even killer genes. Yet some of us value these animals more than we do the cross-breeds and mongrels. In the natural world, those animals most vulnerable to extinction tend to have the least genetic diversity. They no longer have the flexibility to adapt to changing environmental conditions, or they cannot breed out harmful genes.
Going back to the white-headed ducks, it turns out that they are suffering from a genetic bottleneck and have been unable to respond to pressures such as hunting and habitat change. By accepting their ruddy suitors the female white-headeds may actually help protect the species by introducing much-needed new blood. But no, the hybrids are not white-headed ducks and must be eliminated. Well done Spain.
Domestic animals and plants cause all sorts of upset too. Now where the difference between wild and domestic really lies deserves a blog of its own, but in most cases domestic species are still closely enough related to their wild ancestors that they can still reproduce with each other. Enter the domestic cat!
Not content with killing our native birds and mammals (the task they were originally brought here for), the domestic cat, felis catus, has had the gall to interbreed with the UK’s only wild cat, felis silvestris silvestris. The Scottish wildcat is a remnant population of the European wildcat, which is itself considered to be a sub species of the wildcat felis silvestris which ranges across Europe and Africa and from which all domestic cats are descended. While our Scottish population is under great threat, the species as a whole is not in danger.
The Scottish wildcat has suffered greatly from hunting and habitat loss, and more recently from interbreeding with domestic cats. As with the ruddy duck, this raises some interesting questions. If the cats are related to each other, and choose to breed together, what’s the problem? Also, we think that cats initially domesticated themselves, so should we get worried that domestic cats eat (or at least kill) our wildlife, and should we worry at all that the Scottish wildcats have taken a fancy to their domestic cousins?
I think that if the cats don’t have a problem mixing, and the hybrids do all the things the ‘pedigree’ wildcats do, we should just leave them to get on with it. It may even be good for our wildcats to get a bit of a genetic refresh. If we take the view that cats domesticated themselves anyway, we can feel even less guilty about all the naughty things our moggies get up to. It’s true that most domestic cats are well fed and kill things seemingly for the fun of it, but certainly our feral cats do no more or less than the wildcat would if we hadn’t persecuted it and driven it to the wildlands of Scotland.
So I say let’s all be a bit more sensible about our relationship with our fellow earthlings. Live and let live. If we have taken advantage of other species (or they have taken advantage of us) let’s not worry so much if cousins take a shine to each other, as the ruddy duck and wildcat examples highlight. We are not the genetic police. Nature usually knows best, and I reckon both the white-headed ducks and Scottish wildcats will actually benefit from their breeding choices, even if their offspring no longer carry the right paperwork.
Ruddy duck v white headed duck
Defra ruddy duck project: https://secure.fera.defra.gov.uk/nonnativespecies/index.cfm?pageid=244
Scottish wildcat v domestic cat
Scottish Natural Heritage: http://www.snh.gov.uk/about-scotlands-nature/species/mammals/land-mammals/wildcats/
More wikipedia links
Genetic pollution: http://en.wikipedia.org/wiki/Genetic_pollution