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Unusual behaviour noted since I've been here

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Alan Hyde View Drop Down
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    Posted: 09 Aug 2017 at 5:04pm
Ok , Over these past years I noticed some quite worrying unusual behaviour in our native snakes 
Grass snakes locked together near the hibernaculum before going in brumation . 
A female adder that emerged from hibernation gravid . She gave birth in June to 17 neonates , all male 
A grass snake I had that was a rescue from a building site . It did not mate , laid 13 eggs , all were male 
A melanistic male adder locked into a large female , outside the hibernaculum Feb 4th 
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Iowarth View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Iowarth Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2017 at 7:31pm
Sadly I can't point you to actual posts but we do have some reports of snakes producing young very early in the year and gravd appearing animals immediately before hibernation. Similarly, a few years back, I saw a successful mating of sand lizards in late September - the male had even lost all his green - but clearly not his enthusiasm.
I can't help thinking that climate change may be having an effect - we have often seen good weather carried right into December down here on the south coast, together with unseasonably wet and or cold spells in the summer. Are these changes creating triggers to breed? And if so, is this actually worrying or simply animals adapting to environmental changes?
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Alan Hyde View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Alan Hyde Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2017 at 7:47pm
Hey Chris , great that I'm not alone and others are seeing this . The one that really interested me was the female grass snake that produced all males . Parthenogenesis, sperm retention . 
I also wonder if these changes are due to climate change , and the regular flooding over these past years .
Cheers , 
Al
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Iowarth View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Iowarth Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 2017 at 8:31pm
I suppose, Alan, that the first thing we need to consider is whether it was just one of those things. My experience of incubating many species that don't have Temperature Dependent Sexual Determination in incubation is that offspring average about 50/50 which seems reasonable. BUT, that average can include clutches with something like 80/20 in either direction. So, there is a fair chance that where TDSD is not present it's down to the luck of the draw which in turn means that sooner or later one will get a clutch with 100% of one or t'other (which I have experienced - albeit rarely).
I don't discount sperm retention (which is unlikely to affect sex of offspring!) as it has appeared in quite a few species but, in this instance, I do discount parthenogenesis as this (unless they have invented a whole new way of doing it!) should produce only females!
But, that doesn't mean there may not be some other unknown factor influencing this.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote VickyS Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2017 at 9:08am
I had always understood this was fairly normal behaviour but could be wrong!
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Caleb Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2017 at 11:20am
Originally posted by Iowarth Iowarth wrote:

I do discount parthenogenesis as this (unless they have invented a whole new way of doing it!) should produce only females!

Parthenogenesis can produce males in species with ZW sex chromosomes- in this system males are ZZ and females are ZW. This has happened in Komodo dragons- lone captive females have laid fertile eggs that produced only males:

Snakes usually have ZW sex chromosomes, so it would be expected that parthenogenesis would produce only males. 

There are some exceptions- it was recently discovered that some boas and pythons have XY chromosomes (and so produce only females if parthenogenesis occurs):
Presumably the parthenogenetic blind snakes also have XY sex determination (or at least they would if any males ever existed).

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Post Options Post Options   Thanks (1) Thanks(1)   Quote Iowarth Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2017 at 11:31am
Thanks Caleb - that had slipped my memory - rapidly escalating senility!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote GemmaJF Quote  Post ReplyReply Direct Link To This Post Posted: 10 Aug 2017 at 2:02pm
Hi Al, yep still here Big smile

I think it was Will that first mentioned on here a suspicion that snakes were leaving hibernation gravid a couple of years ago. A case of is this something that always went on and we just know now from sharing info, or is it new and possibly a reaction to climate change? I would guess we can assume new if it is being observed at sites that  have been monitored over decades and the behaviour was not noted in the past. Or at least assume that at that particular site things are changing.
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will View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote will Quote  Post ReplyReply Direct Link To This Post Posted: 11 Aug 2017 at 11:52am
Hi Al / Hi All

thanks for the plug, Gemma - yes, it's something that's had me interested for some time.  I think all our species of snake, plus slowworm, can and do produce young outside the 'normal time' (because they haven't read the books...)

A sample of 3 likely-looking smooth snakes turned out to have well developed young this spring in Dorset - confirmed by ultrasound - I need to write this up officially, but too busy / lazy!  Also grassies and smooth snakes regularly seen mating in late summer / autumn.  Female adders basking away from all the hustle of mating animals also look gravid to me, but I have yet to be able to capture and ultrasound them to prove it.

My feeling is that they have always done this, but now we're actually starting to look!
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