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Do covers used for surveying benefit reptiles? |
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Suzy
Senior Member Joined: 06 Apr 2005 Location: United Kingdom Status: Offline Points: 1447 |
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Posted: 26 Feb 2013 at 1:59pm |
Sorry if this question or subject has been discussed before. I don't remember it, so here goes...
In placing tins of felt or other materials as covers to enable surveying, is the habitat being made more beneficial to the reptiles? In raising the body temps do we help them to digest their food quicker, shed their skins more speedily, reach breeding condition more quickly after hibernation etc? Have any comparisons been made of the health of a population at a site with covers against one with no covers? To help avoid variables it would seem best for maybe a site to be split in half, with one having no covers. Would the half with no covers show a movement to the half with covers? Maybe this is already researched and written up somewhere. I notice on this site that high saturation of covers is mentioned at times. Again is this even better than 6 sets of five tins widely scattered? Overall I'm wondering are covers beneficial for reptiles or just spreadsheets? |
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Suz
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GemmaJF
Admin Group Joined: 25 Jan 2003 Location: Essex Status: Offline Points: 4359 |
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I think one can easily argue that they improve a habitat and could increase carrying capacity.
Things like the fact gravid animals often sit under them all day and also factors such as male common lizards can be quite territorial about prime natural basking spots and then don't need to be when there are a lot of felts. So anecdotally I would say they offer 'benefits'. It brings up a couple of things I've observed down the years. 1) Finding grass snake in marginal habitat where felts were placed next to optimal habitat. I thought it unlikely they would have been present much at all if it were not for the felts being in place. It led to the conclusion that the management scheme at the site benefited grass snakes, when it fact it was kind of rubbish and well over mowed. 2) Consultancy practice of leaving survey felts down at mitigation sites for long periods before planned capture. It is not a good idea, it can encourage animals to stay in the mitigation area which will then need to be moved! 3) In situations like wildlife gardens, providing them can be an easy way to provide extra good habitat. I leave them down in ours, not just because it makes it easier to locate the animals, but also because they provide extra basking opportunities.
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Suzy
Senior Member Joined: 06 Apr 2005 Location: United Kingdom Status: Offline Points: 1447 |
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Interesting Gemma. Thanks for replying. So I guess in seeking to monitor populations we are in fact having some effect and it can't be considered a neutral action.
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Suz
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GemmaJF
Admin Group Joined: 25 Jan 2003 Location: Essex Status: Offline Points: 4359 |
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It depends really.
If one is looking to detect presence only during a short term survey the results are likely to be indicative of natural occupancy. It would be unlikely for example if they were down for a matter of months they would significantly alter occupancy levels. One can't argue though that the felts are entirely neutral and for sure very long term study that provides numerous felts in a given area must consider that they may have some effects such as concentrating animals into the survey area. Low density of felts over very large survey areas would reduce these effects but it all really comes down to the fact that anyone carrying out surveys needs to be able to interpret the results. At the very least some consideration should be given to whether or not the survey method was neutral and giving a true picture of occupancy. Sadly what I see too often is people thinking it is some how easy to survey for reptiles with felts. It's more a case that it is convenient in terms of positive results compared to say visual searching which would be more (but not necessarily completely) neutral. In a way it is similar to the results at sites where they trash all the habitat and claim they see a lot of animals. The poor things are resorting to the only cover available, so of course they see a lot of them. It won't last in the long term and it is not a neutral picture of what was happening before the action was taken. It takes more thought than a simple snap shot to draw any useful conclusions.
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Robert V
Senior Member Joined: 06 Aug 2004 Location: United Kingdom Status: Offline Points: 1264 |
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Any home range and local population undergoing study should not be monitored in such a way so as to draw attention to the area (such as grid referencing using stakes and marker tape, or high numbers of ground sheet refugia!). Anything that encourages attention to the animals such as the prominent and obvious installation of Artificial Covered Objects (ACO’s), inevitably leads to disturbance and which is likely to be detrimental in the long term. In these studies, “Tins” (ACO’s) were not used as in the opinion of the author they can often provide a disproportionate population indicator in that snakes using such refugia were not then inclined to move as freely as at sites where no such cover existed. “Tins” placed at locations known to contain reptiles could simply encourage reptiles to remain and encourage indolence in species which are supposed to travel and / or migrate! Fallen logs and more natural field cover which can take years to provide suitable day-time refugia will help build a natural course by which many generations of snakes will follow by scent trail and indeed, the ditches, and similar passages provide the normal migration corridors which may not be used if man-made refugia is placed, especially if they become attractive to toads and newts. The whole home range mapping can then become an unnatural falsification of local population numbers. Figure 12: Basking area 2010 prior to the installation of Artificial Covered Objects Note the natural migration movement across site during summer. Three study sites included an enclosed farm site without public access and surveys were undertaken in the summer of 2010 and which showed regular basking areas for Grass Snakes to be beside a hibernacula beneath tree roots in a raised south facing bank and adjacent to natural ‘obstacles’ such as fallen logs, stumps etc, which had appeared over the course of time, to be utilised by different members of the group in a circular migration movement around the site. In the autumn, tins were placed at strategic positions around Plate 67: Overhead shot from balloon which sets out the details of the farm site. the pond and from there along the migration ditch and stream which also included many of the natural refugia sites back to the vicinity of the hibernacula used by most of the group. Figure 13: Comparative study of sightings in 2011 – note the reduction in sightings generally In the Spring, surveying of the site was again instituted and it was found that upon emergence from hibernation although the snakes appeared as expected close to the hibernacula, during the following weeks they began to ignore the more natural refugia in favour of the tins and individual snakes could then be found under the same tin repeatedly, until hibernation again drew close in October / November when most of the group could be found again in the vicinity of the hibernacula. The most striking aspect of this preliminary study is not only how the preference changed from natural refugia to the Artificial Covered Objects, but also how the previously recorded migration around the site was not observed in 2011, but instead the individuals maintained a presence under tins much closer to the hibernacula and for all year round. Figure 14: Recorded observations under tins in 2011 compared to more natural refugia Observation point numbers 3 and 5 for instance, which in 2010 recorded a steady level of sightings in summer suddenly ceased in 2011 to have anything like the same number and whereby the mid point on the site was seemingly abandoned in favour of ACO’s close to the hibernacula and point 2. |
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RobV
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Robert V
Senior Member Joined: 06 Aug 2004 Location: United Kingdom Status: Offline Points: 1264 |
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This is an excerpt from Grass Snakes 3rd Edition, which I am not placing on here as self promotion but because I beleieve ACO /Tins do alter the movement of Grass snakes. I have sent my findings to the Uni of Kent and if anyone would like to see the graphs of results I'll post them on here, its over to you guys.
R
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RobV
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Suzy
Senior Member Joined: 06 Apr 2005 Location: United Kingdom Status: Offline Points: 1447 |
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Thanks Robert. All very interesting.
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Suz
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AGILIS
Senior Member Joined: 27 Feb 2007 Location: United Kingdom Status: Offline Points: 1689 |
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Hi I would like to mention that more smoothsnakes are to be seen under refuges put down then what you would see in the open ,I have been very lucky in my open natural sightings on certain areas. but would certainly say refuges make life easier on us seeing them and they seem to like the shelter it provides for them otherwise they would not be there. Also I agree with Robs comment on making these sites to much high profile as some dog walkers or passing trekkers will lift tins up out of curiosity and quite often shriek out snakes and bash their brains out . Keith
Edited by AGILIS - 28 Feb 2013 at 8:18pm |
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LOCAL ICYNICAL CELTIC ECO WARRIOR AND FAILED DRUID
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GemmaJF
Admin Group Joined: 25 Jan 2003 Location: Essex Status: Offline Points: 4359 |
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I don't think anyone would mind Rob if you self promoted on the forum in any case, we might have pulled your leg about it in the past but it was just banter.
Anyone who hasn't got a copy of Grass Snakes by Robert Vaughan, go buy it! I think grass snakes are very good example to use for modification of behaviour occurring due to felts. It's one of those topics where we have to be a little species specific though I think, for example slow worms are less mobile and refuge survey might provide a fairly accurate indication of natural occupancy. For sure there are cases as Keith as highlighted that without felts we may simply not detect animals that we need to know about. So felts have a place in surveys, we just need to think when they are appropriate and when they may skew results.
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Suzy
Senior Member Joined: 06 Apr 2005 Location: United Kingdom Status: Offline Points: 1447 |
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I wasn't very clear in the first place about time spans for various covers. I was more thinking of places which have them down long term - i.e. all the time - and not ones that are put down for a specific short term monitoring project.
I figure you professionals who put down lots will gather them up afterwards for use elsewhere, whereas some places they are left long term, but that depends on various factors. Yes sadly many are placed in full public view or go walk-about or are disturbed with joke items being placed under them. If I visit a new place and want to find tins I figure they will be just a few paces off the path and I'm usually right. From all I read, smooth snakes are almost impossible to see without tins. Hopefully one day I'll see one. |
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Suz
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