reasons to explain adders absence: |
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evilmike Senior Member Joined: 15 May 2004 No. of posts: 85 View other posts by evilmike |
Posted: 17 Sep 2004 on the south Wales coast there are two dune systems, one at Methyr Mawr and the other at Kenfig, at kenfig there are common lizards and grass snakes but no adders, at Methyr Mawr there are adders and i imagine both other species. trying to think of a possible reason why adders havent choosen to or been able to settle at kenfig, there very close to each other being on the same stretch of coast, any one have any ideas? Mike Lister BSc hons Ecology & Env management |
calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351 View other posts by calumma |
Posted: 17 Sep 2004 Never exclude random chance! Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090 View other posts by GemmaJF |
Posted: 17 Sep 2004 Hi Mike, I've seen the same a couple of times before, adjacent habitats one with adder, the other without. Taking it to individual site level I find adder will use specific areas and be totally abscent from the rest of the site that looks at first to be equally as good. Factors such as basking opportunity, cover and food source play a part in this and though difficult to measure in the field, may give clues as to why one area of habitat has been colonised and another apparently similar, has not. Also consider that adder can be very 'traditional' with regard to hibernacula, basking areas and foraging grounds. I agree with Lee though that it could just be down to chance. I'm currently surveying a site that looks ideal for slow-worm, plenty of vivi lizards are showing and grass snake are known to be present, so far not one single slow-worm and none have ever been reported.. if they are abscent I can see no good reason other than slow-worm have not reached the site in sufficient number to establish a viable/detectable population. Gemma Fairchild, Independent Ecological Consultant |
Matt Harris Senior Member Joined: 03 Jun 2003 No. of posts: 196 View other posts by Matt Harris |
Posted: 20 Sep 2004 There is a lot less scrub at kenfig than at Merthyr Mawr, and also the latter is much more diverse in terms of habitats. Kenfig is mostly fixed, grey dune and there isn't really that much cover for Adders. Perhaps this has comething to do with it? Gwent Amphibian and Reptile Group (GARG) |
evilmike Senior Member Joined: 15 May 2004 No. of posts: 85 View other posts by evilmike |
Posted: 20 Sep 2004 M Mawr does have more dense veg on a wider area but i still think kenfig has enough suitable to allow for adders, certainly other factors should all be favourable. Kenfig is being left to natural succession if i remember correctly and there are areas of good scrub and woodland, especially by the lake which i would guess would be excellent summer hunting grounds. Chance may be the key or habitat choice, i dont think that there there in such a small number as not to be found as the site is too widely walked etc mmmmm good question this :) thanks for ya ideas Mike Lister BSc hons Ecology & Env management |
Matt Harris Senior Member Joined: 03 Jun 2003 No. of posts: 196 View other posts by Matt Harris |
Posted: 20 Sep 2004 About a year ago I wrote a Site Management Statement for Kenfig SSSI, and current opinion is that it needs more grazing to stop the grassland from becoming rank and to combat natural succession to scrub. I think there might even be some fencing going up to keep sheep and cattle in. Arguably this may reduce the suitability of the site for snakes. Dave carrington of Bridgend CBC is the one to ask. Gwent Amphibian and Reptile Group (GARG) |
evilmike Senior Member Joined: 15 May 2004 No. of posts: 85 View other posts by evilmike |
Posted: 20 Sep 2004 yeah i know Dave, due to do some work exp next month when i hand my MSc dis in next week, if grazing is their approach then yes i'd agree with the loss of site suitability there, how much high ground is there, not a great deal for hibernation sites? 2/3rds floods in winter if i remember correctly could have a good reason here, not to sure on n natrix hiberntion whether its similar? Mike Lister BSc hons Ecology & Env management |
GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090 View other posts by GemmaJF |
Posted: 20 Sep 2004 Mike, berus and natrix will share the same hibernacula, so one could presume requirements are broadly similar. (adder hibernaculum are known to range from grass tussocks to the more obvious rotten tree stumps, banks and mounds). I would place hibernation opportunity very high on a list of criteria if making an assessment of a sites suitability for adder. Gemma Fairchild, Independent Ecological Consultant |
Tony Phelps Forum Specialist Joined: 09 Mar 2003 No. of posts: 575 View other posts by Tony Phelps |
Posted: 22 Sep 2004 I recorded adders at Kenfig in 1979 - have not been back since - my main study area is of course Cors Caron in Ceridigion. Good adder pops around Gower. Tony |
calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351 View other posts by calumma |
Posted: 23 Sep 2004 Mike, You seem quite sure that there are no adders at Kenfig. Could it be that there are simply not yet detected? My own survey work has shown that adder can be difficult to confirm from some sites. It has taken just over a year of fairly intense effort to confirm adder from one site where we know that they are present! Remember it is easy to confirm presence, but nigh on impossible to *confirm* absence - only predict it. Even if animals are absent from a site one year, who's to say that they won't recolonise it in a year or so? In Kent, we have just reconfirmed adder from 2 sites where that have not been recorded since the late 1960's! Given Tony's observations above, I would recommend that you review your survey strategy at the site. Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090 View other posts by GemmaJF |
Posted: 23 Sep 2004 Mike, I'll back Lee up on this 100%, I surveyed a site in 2003 intensively for adder. It took 12 visits to record the first individual, a neo, using both refugia and visual techniques. It was only returning this year in the early spring that I caught up with the main group emerging form hibernation and established that a good population was present. This was only possible by focusing visual survey around the immediate area where the neo was recorded the previous autumn. Having said this, I also managed to find 3 gravid females within 60 seconds of stumbling out of the car at a 'new to me' site this year, as Lee said it's often easy to establish presence, absence is a whole different ball game! Gemma Fairchild, Independent Ecological Consultant |
Tony Phelps Forum Specialist Joined: 09 Mar 2003 No. of posts: 575 View other posts by Tony Phelps |
Posted: 23 Sep 2004 As I am a 'Surrey' boy for a week before I fly out to SA, I thought I would visit an old site of mine on the edge of Chobham Common. Found two females very recent post-birth and a total of eight neos within ten sq m. Also a good number of males (5) all in the same location. If this was Dorset males would be still well dispersed - could this unsettled weather be promoting an earlier return to hibernacular. I must add that all males were in splendid condition, and two were in the 'blue'. Going back tomorrow have another look, weather looks more promising. Tony |
evilmike Senior Member Joined: 15 May 2004 No. of posts: 85 View other posts by evilmike |
Posted: 23 Sep 2004 thats interesting, i have survyed the site only one day and it is a huge site, nice pic of a common lizard, but was told no we dont get adders here only grassies by the warden, hes done the job for years and is there everyday seemed very certain of the lack of adders. brings up more questions and uncertainties hehe dam this disertation :P
Mike Lister BSc hons Ecology & Env management |
GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090 View other posts by GemmaJF |
Posted: 23 Sep 2004 Mike, I'm currently surveying a site where the warden reliably informed me it was a bad year for adder, I'm recording on average 6 adults per visit, can't wait for a 'good year' :)). I have a couple of sites where locals will tell you adder are absent, at one I recorded 18 in single morning this year. Remember, if they ain't looking for nadder they won't see.. and chances are if they are, they still won't!!!!! Gemma Fairchild, Independent Ecological Consultant |
GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090 View other posts by GemmaJF |
Posted: 23 Sep 2004 Tony, I've noticed males moving back to hibernation areas here in Essex at a couple of sites. I've been a bit suprised to see them lying out much as they do in the spring, has been very unsettled here also. Gemma Fairchild, Independent Ecological Consultant |
Tony Phelps Forum Specialist Joined: 09 Mar 2003 No. of posts: 575 View other posts by Tony Phelps |
Posted: 23 Sep 2004 Yes Gemma, I would call the aggregations witnessed at Chobham on a par with spring emergence, which is most unusual. Like I said gonna go back tomorrow, and also shoot some movie as a sort of intro to my SA Video Diary for C4 (were all at it you know!) T |
Tony Phelps Forum Specialist Joined: 09 Mar 2003 No. of posts: 575 View other posts by Tony Phelps |
Posted: 24 Sep 2004 Went back to Chobham site today - a total of 19 adders, only three of which were adult female all in good condition (non-breeders) Two cracking melanic males. Males were in singles and groups up to three, and three immature females and two neos. Four grass snakes, one which was coiled with two male adders. Sorry no stills, but got some nice movie. T |
evilmike Senior Member Joined: 15 May 2004 No. of posts: 85 View other posts by evilmike |
Posted: 24 Sep 2004 is there any idea on mortality on females when they give birth? imagine must put them through some stress taking that they need a year off to recouperate before breeding again. the thing that still amazes me is the paper infront on me now 'beyond hypothesis a long term study of british snakes' Phelps T, June 2004 British Wildlife, where tony found the same adder and smooth snake making them over 30years old! did you see them between 1976 and 2003 or were there good at hide n seek? Mike Lister BSc hons Ecology & Env management |
Tony Phelps Forum Specialist Joined: 09 Mar 2003 No. of posts: 575 View other posts by Tony Phelps |
Posted: 24 Sep 2004 A biennal reproductive output represents absolute maximum for adder - more likely to have longer gaps - 3-4 years - also females breeding on maturity(4th season) almost always die. Females that postpone until 6,7.8. years go on to live a long life, or potentially so. Yes, I have seen my 'old' snakes regularly since first recorded. T |
evilmike Senior Member Joined: 15 May 2004 No. of posts: 85 View other posts by evilmike |
Posted: 24 Sep 2004 thanks for that info Mike Lister BSc hons Ecology & Env management |
- reasons to explain adders absence |