Pigeons at Bunhill Fields in the City of London
Dear Readers, I was reading an interesting article in The Guardian today, and thought I’d find out what you think (and share some of my thoughts). It appears that scientists are working very hard to find a way of persuading various ‘pest’ and ‘invasive’ species, from feral pigeons to grey squirrels to wild boar, to ingest contraceptives in order to control their numbers. This is the ‘holy grail’ of control methods, but it remains to be seen how practical or effective it will be, and also whether there will be unintentional side effects.
Some species of animal, such as the grey squirrel, have become an intrinsic part of the wildlife of the UK, but they are associated with the decline of the red squirrel and blamed for £37m worth of damage to timber through bark stripping. A study, that proposes using contraceptives in hazelnut spread, is aiming to find a more humane way of reducing the number of squirrels than trapping or shooting. One problem has been finding a hopper that can only be opened by grey squirrels, so that it could be used in areas where both red and grey squirrels are present. In spite of the headline for The Guardian article, no contraceptives have yet been used in the field, while research continues to see which levels of the medication would be safest and most effective.
The University of York is hosting the first ever workshop on Wildlife Fertility Control, looking at not just the issue of contraceptives for squirrels, but also for pigeons, parakeets, rats, wild boar and deer. Contraceptives have been used with wild boar in Europe, but at the moment it involves delivering the drug by injection – clearly, an oral contraceptive would be cheaper and less dangerous for humans and animals. Contraception has also been used on elephants in the Kruger National Park in South Africa.
However, I have questions. First up, there is a clear correlation between pigeon numbers and the amount of food available to them – reduce the food, and you get less pigeons. It seems as if better litter bins and less waste food would bring down the number of birds over time, without having to resort to feeding them ‘the pill’. This is probably also the case with a number of other species. Shouldn’t we simply be a bit tidier and less messy?
More worrying, for me, is the potential impact on not only the animals who ingest the contraceptive, but also on the animals that feed on them. What if a peregrine falcon eats a pigeon who has been treated with ‘the pill’, or an owl picks off a rat who has been similarly treated? Of course, the use of poisonous chemicals to kill ‘pest’ animals, particularly rodents, also has a terrible effect on their predators, but the cumulative effect of eating prey animals laced with contraceptive may also have an effect on the breeding potential of some of our rarest birds of prey.
And finally, the effect of human urine that contains the residue from the contraceptive pill and ends up in our rivers has been shown to have a feminising effect on the fish who swim there.
As with so many things, we’ve made a massive mess by moving animals from one place to another, and providing the conditions that have resulted in some animals proliferating without any natural controls. Using a contraceptive is one way to try to sort things out, but it will undoubtedly have side-effects, both predicted and otherwise. It will be interesting to see if any of these research projects actually result in reducing the numbers of the targeted species, or if nature will, as usual, find a way around human controls.
What do you think, Readers?
Food for thought indeed. I agree with you re the amount of food lying around or that is easily accessible for, say, pigeons and squirrels. We were inundated with (indigenous) speckled pigeons a year or so ago: up to sixteen pairs breeding in under our roof. Not only was this unpleasant in terms of their droppings, but they wolfed up all the bird seed I put out. I stopped providing seed for at least a month and we had our eaves closed in. No food and no shelter. The upshot is that we now only have one pair that roosts on a ledge overnight … the others have found homes elsewhere.
Food and shelter are key resources for most creatures, so it’s interesting to see how it works in practice!
I always get really uncomfortable when we start talking about ‘invasive’ and non-native species and how we should control them, because there is always going to be an element of making species into ‘good’ and ‘bad’. Although I can understand things like eradicating rats from islands where they are decimating the bird populations, I think we’re the ones who have usually done the damage in the first place and I worry that interfering more will only create more problems in the future. Having said that, I’d rather we used contraceptives that killing. I love pigeons – they have a really bad rap I think, and often for people who live in towns, they’re one of the few ways people can interact with wildlife.
I agree – we cause the problems and then, if we’re not careful, we mess things up even more by trying to undo the damage. Plus I agree re the invasive species stuff, which often plays into a particular kind of mind set. I agree also about getting rid of populations of creatures on islands – Lundy has had a dramatic resurgence of puffins and other seabirds since the rats were eradicated. And I say that as someone who is very fond of rats!
I guess it comes down to how much of the chemicals can be passed on. I presume there is a way to check the levels retained in the animals which have been given the ‘pill’. E.g. Does 100% of the chemical intake become 30% or 10% or whatever in their body? Though perhaps even a tiny fraction might upset the balance.
An interesting thought, Mike – the scientists are being very cautious, and rightly so in my opinion. So often when we try to sort out a human-made ‘problem’ we end up making things worse…
Enforced contraceptives for wildlife? Very cautious about this. Remember Myxamatosis back in the 50s and 60s? An example of well-meaning control with disastrous unintended consequences. (Might be OK for the wasps in our garden though!)
My Dad was doing national service at the time of myxamatosis in the UK, and had to walk through the fields of Essex knocking the poor blind rabbits on the head with a stick to put them out of their misery. He never forgot it…
I think it’s a terrible idea. The contraceptives will persist in the environment, directly affecting predators that eat the squirrels and pigeons and indirectly affecting everything else.
As you say, pigeon populations would reduce if we stopped leaving souch waste food around. I believe pine martens are a good deterrent to grey squirrels too.