All animals used in the present study were already found dead (road-killed), and therefore an ethic approval is not required.
You know, sometimes I see a study (this one was tweeted around a few weeks ago), and you just sit and wonder WHY. Why did scientists DO this study, why was it necessary? What is its purpose in life? I mean, this one must have a purpose. It’s not like most people WANT to drive around counting and assessing the state of roadkill.
And indeed, this study DOES have a purpose. And it’s more than staring at roadkill.
Santos et al. “How long do the dead survive on the road? Carcass persistence probability and implications for road-kill monitoring surveys” PLoS ONE, 2011.
There are a LOT of roads in the world, particularly in developed countries. Where there are roads, there are generally cars. And these roads, and these cars, are going to have an impact on the environment around the road. The migratory patterns of the animals for example, not to mention the number of animals that like a piece of nice warm blacktop on a sunny day (snakes are a good example of this. Also armadillos. Especially armadillos. Ask a Texan). So where there are roads, and cars, and animals, well, animals are going to get hit by the cars. This means cleanup work, and efforts by ecologists to try and prevent some of roadkill carnage. And this means that you have to actually figure OUT just how much roadkill there is. For this, you have to know how long a given piece of roadkill is going to remain on the road before getting eaten or squished into something entirely unrecognizable. If you’re only driving around once a week, you may not catch all there is and your numbers may not be reliable.
This requires dedication. This requires scientists driving around in a truck over the same patches of road, day after day, counting roadkill.
Let us have a moment to pause and think of those poor scientists, and for our eyes to water on their behalf. For truly, they have sniffed the stink of many dead skunks.
TO THE ROADKILL!
The scientists observed over 4,000 specimens in a typical Mediterranean forest in Portugal, over a period of about a year. The vast majority were small birds, salamanders, and toads, and the rarest roadkills were turtles. By far. Considering the slowness of the turtle, I think we need to think for a moment about their possible craftiness when faced with roads. A few large carnivores and large birds were represented as well. There were also 82 bats. BATS. This is the point where I looked up and exclaimed to Mr. S “people hit BATS while driving?!” If you are a person who has done this, please report in.
But the other question is, how long do these carcasses PERSIST? After all, dead meat is dead meat, and to many animals dead meat is tasty. Not only that, you’ve got other cars coming along to squish your carcass into oblivion. So the scientists came back day after day, each time they found a new carcass, to see how long it lasted. From this, they computed the somewhat amusingly named “survival curve” (for the survival of the carcass, obviously, the animal’s been toast for a while).
You can see that the toads, salamanders, and bats had by far the worst of it. Though the toads and salamanders were among the most often hit, they, along with the bats, persisted in most cases for less than a day. Too much traffic on some very soft anatomy. The longest persistence was credited to the carnivores, the large birds of prey, and hedgehogs, which had a 40% probability of making it to 15 days by the side of the road. In the middle you’ve got your small mammals, your bunnies, snakes, etc.
So what does this show? Well it mostly shows that other estimates of roadkill had a lot of bias, being biased toward carnivores and the larger animals, because those were still around when the trucks came by. Most other estimates show toads and salamanders and such represented pretty low, but this study indicates that this is because they just don’t make it that long.
But it makes me wonder. This was Portugal. They don’t really report things like deer (do deer live in Portugal?). How would this differ in parts of the US? What is the persistence time of armadillos? What of skunks? Clearly we need to be eyeing our roadkill more carefully. It might be gross, but it can tell us a lot about what gets hit, why, and when, and can help us find ways to save some animals from that deer in headlights look.