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Impact of surveys: |
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rhysrkid Senior Member Joined: 14 Nov 2003 No. of posts: 98  View other posts by rhysrkid |
Posted: 12 May 2005 Hi I am into my second season of grass snake surveys and a couple of issues have come to my attention which I hope an expert or two in the forum can comment on. I am more than aware that all too often work carried out such as habitat management or radio tagging individuals etc can be done with the best intensions but can actually do more harm than good unless carefully researched, which made me question the ethics of my surveys. In order to monitor populations I have been capturing individuals and photographing neck and belly markings to identify individuals (which has been very successful with a population so far around 20 individuals on a site of about 11 ha, of which 5.5 is open water). Handling times are kept to a minimum but inevitably there is some discomfort experienced by the individuals. I carry out surveys approximately once per month. What if any, is the cost of predator avoidance behaviour such as the excretion of anal fluids or playing dead? Does handling like this affect their behaviour post capture - i.e. hunting success/mate finding success etc. Most of the snakes caught are young or juvenile - does anyone feel that handling like this will impact upon their overall fitness? The data is providing some interesting info on the snakes basking site fidelity and movements. However, obviously the welfare of the snakes is far more important than the population data. Attempting this sort of survey has not been possible without capture as the photos taken simply do not reveal enough information. Any thoughts on this matter would be very much appreciated, although I appreciate that it is unlikely anyone has done a study on this topic! In addition, I will be supplying records at the end of this season for anyone who is interested. Thanks
Rhys |
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Tony Phelps Forum Specialist Joined: 09 Mar 2003 No. of posts: 575  View other posts by Tony Phelps |
Posted: 12 May 2005 One develops ones own code of ethics over the years. With adders for example, I never handle adults during the mating season. My old snakes are living proof that mark & recapture has no negative effect - same for smooth snakes. Not all snakes are so cooperative. If you catch and mark a large elapid, cobra/mamba, at its refuge it will desert never to return. On the other hand such as puff adders and African rock pythons have shown to be very obliging. I would only add that all 'processing' MUST be done at time of capture on site. Tony |
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rhysrkid Senior Member Joined: 14 Nov 2003 No. of posts: 98 View other posts by rhysrkid |
Posted: 12 May 2005 Thanks Tony. One the main issues I had was that the snakes are generally young rather than adult. Of course all 'processing' takes place there and then (I try to handle as little as is necessary), but when they start to perform predator avoidance behaviour I sometimes feel that, for a young snake, this could be detrimental - remember its the same snakes that are recaptured on each survey. However, I guess if it is that bad they cant remember as they always return to the same spot unlike cobras and mamabas! Thanks for your comments, particularly with reference to breeding season. Rhys |
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Chris G-O Member Joined: 14 May 2003 No. of posts: 36 View other posts by Chris G-O |
Posted: 15 May 2005 Hi, I'd be interested in knowing your findings, especially if you're doing mark-recapture-type population estimation (Jolly-Seber index etc). We have a PhD student who's doing photo-recognition on sand lizards. What's your research for - work , education or pleasure? cheers, Chris (reply off-list if you like to chris.go@herpconstrust.org.uk) Chris Gleed-Owen, Research & Monitoring Officer, The HCT & BHS Research Committee Chair |
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stuart Member Joined: 26 May 2005 No. of posts: 12 View other posts by stuart |
Posted: 26 May 2005 Hi,just joined your forum.Over the last three years I have been surveying a local grass snake population and have noticed that the first appearance of immature snakes seems to be as late as early may whereas I am finding adults as early as second week in march. Has anyone else noticed similar findings? Obviously I appreciate I only have reports for the last three years,and up until this year I have not used refugia, relying solely on personal observation. I am based in Staffordshire. |
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rhysrkid Senior Member Joined: 14 Nov 2003 No. of posts: 98 View other posts by rhysrkid |
Posted: 26 May 2005 The earliest record I have for grass snake this year was the 12th of April and that was a juvenile under refugia (SE England).
Rhys |
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B Lewis Krag Committee Joined: 24 Aug 2004 No. of posts: 146  View other posts by B Lewis |
Posted: 13 Jun 2005 One of my colleagues has been doing a study of grass snakes for a good number of years now here in the southeast and has photo ID'd over 240 individuals with a good number of them being re-recorded/captured each year. I think you are right that if the individual continues to re-appear that it would show little side effects from the short time of handling. My colleague records weight, SVL & TL and also photo's the belly pattern. So in general, your concern is one that we all ask ourselves when surveying with mark-recapture methods and invariably good hereperĘs come up with similar conclusions. Seeking advice from other experts with experience with the species is really the right way to go. Good luck with your surveys. Brett. Lewis Ecology Brett Lewis Photography Kent Reptile & Amphibian Group DICE - University of Kent |
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rhysrkid Senior Member Joined: 14 Nov 2003 No. of posts: 98 View other posts by rhysrkid |
Posted: 13 Jun 2005 Thanks Brett. Sounds like a good site that your colleague is working on! Rhys |
- Impact of surveys |
