Ilian Velikov wrote:Ruggero Morimando wrote:I could make you a list of the causes that in 40 years caused the decline and/or the total destruction of snakes around my house, where I live since 1972, but I can reassure you that at number 1 I will put roadkills.
I'd say you have to switch the places of some causes in your chart. From what you described I'd say those growing in numbers wild boars have a much much bigger impact on your local snake population than road traffic and you'd have to come up with some really solid proof to convince me otherwise. Wild boars would maybe indeed eat a snake and most definitely snake eggs, but above all they destroy snake habitat on a large scale. And there's your number 1 reason for snake decline. If the snakes don't have a network of good places to rest, hunt, hibernate, breed and all of this in close proximity you can be sure there will be no snakes in this area. They would rather die out or move to more suitable places, which by the way could be the case in your area. Why do you think the reason you see less snakes is because all of them died? On the other hand a few snakes killed on the road wouldn't have such an impact on the overall population. Is your area changed so much since you live there? Except for the bigger number of cars are there many new roads built?
Ruggero Morimando wrote:And, please... you cannot compare "road kills" with a sort of "natural predation"...
I meant as in the frequency and number of dead snakes. I can assure you that if you have a lake with a road next to it annually much bigger number of snakes die in the lake or surrounding area from natural predation than on the road next to it.
Ruggero Morimando wrote:And a natural predation as the one by Circaetus gallicus has certainly more selectivity than roadkills, in which every snake that crosses a road or bask over it is killed without distinctions
That's simply not true! Not every snake that crosses the road is inevitably killed. A lot of them cross roads many times and get to survive. As I said it's down to chance.
I'm not saying road traffic can't be an issue especially on small islands, but I think there's many other threats to snake survival on which we should concentrate first if we want to preserve them. And anyway you stated your opinion on what the problem is but I also asked what the solution could be. What do you think? I don't think many of us would be willing to switch back to riding horses or go on field trips in nature by long distance running on foot...? And having said that how many of us even hardcore herp lovers would drive along a road in a considerable speed with other cars behind you for example and break suddenly risking car crash and killing themselves, maybe their family and the passengers in the car behind them to save a baby snake on the road?
You write: That's simply not true! Not every snake that crosses the road is inevitably killed. A lot of them cross roads many times and get to survive. As I said it's down to chance.
But you must read my assertions with some elasticity...
It's "not true" only if while the snake is on that road, on that road passes no car. Or passes a car and TOTALLY casually that car does not hit the snake, without any relationship to a possible "selection".
And as I've written a natural selection mechanism will need thousands of years to take place. Or would you think that with road traffic snakes will have enough time to be selected in a darwinian way by their speed or intelligence to avoid roads?
Your lake example could be right if the lake is big and wild, with only small and few roads around it, or many roads but with few traffic.
Could be wrong with a small lake, with few natural predators and many trafficked roads around it.
As regards my region, Oltrepo' Pavese, yes, I can write and say loud that the MAIN difference from 1970 to 2017 is an increased traffic on roads (I could say e.g. with absolutely no scientific meaning/claim, of a factor from 1 to 1000!) AND the increased presence of wild boards. And, surely, the opening of new roads with the tranformation of rural roads with no traffic to asphalted roads with heavy vehicular traffic.
Other factors are less important in my opinion and experience (which is not poor) and I could speak about them. But then we go totally off topic...