Hence the importance of training to be a good shot, to know one's limits and to stay within them. There's more or less a consensus among pest control airgunners that such a limit can be defined as that distance at which one can maintain 100% of shots within the diameter of a dime. Works for me with the very destructive, introduced species of Eastern Grey squirrels, and for the introduced rats of several varieties as well. Both nest in a number of rooftops in my area, doing extensive damage and leaving urine-soaked insulation and wood in their wake. And that's just the nests. Then there's the havoc they bring to any vegetable garden or nut or fruit tree. I've watched a grey squirrel take one or two bites out of every tomato they can find, then move on to the squashes and take one or two bites there. Considering that many studies have determined these animals are carriers of several diseases known to be dangerous to humans, this food becomes wasted in a second as the squirrel tests each and every item they 'might' like and moves on.
Last November a squirrel tore out some stucco from the outside wall around a wire conduit and started building a nest above my downstairs neighbour's bedroom. My neighbours reported hearing a lot of scrambling around up there, worried it might be rats, so I had a look around that side of the house. Sure enough, the hole which had started as just a tiny crack around an improperly sealed electrical conduit entry point (our landlord isn't very attentive to such things) had been enlarged into a 3" diameter hole. They have very strong teeth. A bit of glass and mortar is nothing to a grey squirrel's hard yellow teeth. It took a couple of days for me to find an opportunity for a safe shot. No trap would have been possible as the hole was 6 feet from any flat surface upon which to set one, besides which there aren't any kill traps sold in hardware stores for a rodent that large. And we wouldn't want to be inhumane about it, would we? The squirrel was taken care of before it could complete the nest and settle in to have a family between floors. Had it completed the task unmolested, as suggested by the BCSPCA (who advise that we wait until the young are weaned, then install a one-way door, wait for them all to go out, then seal the hole), the ceiling would have been filled with feces and urine and would have cost rather a lot in biohazardous waste removal and reconstruction. Moldy rodent urine is not safe in any home. Nor is it cute.
Rats seem slightly less destructive, being less picky eaters than squirrels, but the damage they can do inside walls is well established. You may think your home is well insulated, somehow sealed against them, but if there are rats in your yard they are going to get into your walls. Period. A single breeding pair can become close to 200 animals within a year. Sounds fun when they're scuttling around in the ceilings... My father used to run a hotel in San Francisco and one particularly hot summer had an explosion of rats there. He resorted to the best poison he could find. Result? He had to spend over $10,000 and more than a month of his time ripping out walls and removing rotting bodies. Close to 3,000 rats by the time he was done. Humane traps would have done little to dent such a population. Sometimes the numbers just get too bad and something more drastic needs to be done.
And yes, I am very familiar with feelings regarding cute squirrels. I agree, they're cute. But they have no natural predators in Western Canada. They were brought here without any thought being given to this, by enthusiastic wealthy men who wanted to see their fuzzy tails darting around in parks. Vancouver Island is experiencing a wave of the creatures, moving steadily up-island as they dominate more and more ecosystems with their voracious appetites and often 3 litter per year breeding cycles in our favourable climate. Each female can produce a dozen more of her kind per year here. Very rarely does a hawk or coyote catch one, as they're too quick. The BC Government has issued a request for reported sightings:
http://www.env.gov.bc.ca/wld/documents/ce19breummer.pdf
But this suggests no official measures to counter this expansion which began with the release of a few animals in Victoria. Two releases during the last century in Vancouver cemented their presence, and sightings are now as far inland and North as Kamloops. Another release by a zookeeper in Calgary has had similar results, if slowed slightly by the colder winters there. Red Douglas squirrels are becoming more and more rare in Eastern Grey occupied regions - while it is often suppressed by activist groups, the young of other rodents are often consumed by Eastern Greys. Some activist groups (BCSPCA most notably) seem intent on burying their heads in the sand on this issue. But just ask anyone interested in preserving the native UK red squirrels about this invasive species' ability to dominate. They almost lost their reds entirely, some regions having not a single red squirrel spotted for 2 or 3 years, before airgunners and other efforts started turning the tides. Read for yourself about the efforts of the Penrith & District Red Squirrel Group:
http://www.penrithredsquirrels.org.uk/
There are many similar efforts around the UK organised to fight this introduced menace. And the tide has turned. Reds are being spotted in slowly increasing numbers as their habitats are made available again through culling of the American species.
And then there's the songbird problem. Something I've been very happy to see over the past several years is the strong return of nesting bird pairs around here including a couple of types of Chickadees, hummingbirds, robins, finches, even some flickers who have settled in nicely. Grey squirrels LOVE eating up a whole nest full of eggs, or the featherless hatchlings. A single squirrel can wipe out the offspring of 3 or 4 nesting bird pairs per day. And they do. Last summer I watched a family of finches turned into lunch in about 40 seconds, with me helpless to do anything as there wasn't a safe shot available. The squirrel moved on, bloodied lips and all, to attack my garden below. He didn't last another minute.
So cute, aesthetically, sure. As a child I loved seeing squirrels in the park. I grew up. Are squirrels cute in their behaviours? Not at all. They're worse than domestic cats when it comes to the decimation of bird populations. Please give the facts some thought before judging those who are taking responsibility and humanely dispatching these non-native creatures.