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Michal Szkudlarek wrote:Mark, can You explain why in Your opinion there is a dependence between length of mating season and mating balls commonness?

Well I don't really have much of an opinion, as I have never seen a N.natrix mating ball, I just thought I would share this information I had read. If the evidence from that book is true, then if the mating season is short, the females will all be out at once, so the sex ratio will be relatively equal, thus no competition for females, which may mean less mating balls. But as I stated I think there must be more to it than this – density of population and hibernation site potential etc.

Berislav Horvatic wrote:If a short mating season (at high latitudes or altitudes) should mean more mating balls, then
why should a long mating period in the UK also imply more mating balls? I don't get it.

And if mating balls have rarely been observed in British snakes, this would be in accordance
with a long mating period in the UK, not at odds with it. So why your "Oddly, though,..."?

The wording in italics was from the book, so the "Oddly, though....." sentance aren't my words. I was getting slightly confused on the wording from the book as well. I believe it means in colder climates / higher altitudes = shorter mating season = less chance of mating balls. Warmer climates / lower altitudes = longer mating season = more chance of mating balls. Again I was simply trying to provide more information for the discussion.

But same percent of both sexes will emerge after hibernating to mating, unless females are more termophilic- but they aren't as I know. So, in my opinion sex ratio is constant all the time. Both in high and low altitudes.
Michał

I think it is up to the weather condition.
Last year we had a hot and very dry April, I saw not many mating groups and only small ones, one female and one or two males, rarely three males, but not more.
2010 we had a cold and wet April and I saw not many mating groups and only small ones, one female and one or two males, rarely three males.
But in years with perfect snake-weather-condition, warm and humid, I saw some groups with one female and five, eight, ten males.
All in the same area.

Mark Barber wrote:If the evidence from that book is true, then if the mating season is short, the females will all be out at once,
so the sex ratio will be relatively equal, thus no competition for females, which may mean less mating balls.

But the book you quote says just the opposite, at least to me:

At high latitudes the cold climate permits only a relatively short mating season. As not all females emerge from hibernation at the same time it is likely that the sex ratio will be skewed towards males and this will increase competition for females, and thereby likelihood of mating balls.

Mark Barber wrote:I was getting slightly confused on the wording from the book as well. I believe it means in colder climates / higher altitudes = shorter mating season = less chance of mating balls. Warmer climates / lower altitudes = longer mating season = more chance of mating balls.

But the book says just the opposite, see above.

What I'm talking about here is logic, not biology. I'm no mind reader, I read what has been written.

Of course, if the quoted thesis is biologically unsound (= not verified) as such, then it does not matter after all.

At least, the info from the book (as understood like Bero & myself), fits with the garters from N America...

Today I have found out that in 1987 near Nowa Sól there was a mating ball consisting of at least 70 grass snakes with over a dozen of them being females.