Number of clear trap days

5 clear capture days probably originated from the GCN mitigation guidleines. Though I have also heard it quoted in conjunction with Highways projects in reference to reptiles.

The advise I've been given by EN in the past is that ultimately it is the decission of the consultant as to whether sufficient capture effort has been applied.

I agree with this stance. For example I could feel that ACO capture had served its purpose and judge that the site should be destructively searched - should one wait for 5 - 10 days to carry on pointlessly checking cover objects if it is strongly felt that capture effort by ACO is no longer effective?

Be very interested to hear others views on this and also if there is any published reference for reptiles.

Perhaps of some help, this is my preferred method of keeping a handle on reptile mitigation works. From an area of a current mitigation we are working on.

Temperatures have been reasonably constant during the capture period, there are a couple of obvious days where it rained heavily etc but I think in all it is pretty clear what is happening from the graph. We expect a new peak tomorrow (showers today, sun out tomorrow with max 18 c)- this will be very informative as conditions should be ideal for ACO obs.. certainly if the decline in observations in this area continues we will have a good indication we are nearing a point of diminishing return.

The more I think about this the  more I think a set number of CTDs is very arbitary for reptiles. Should we be looking towards using another criteria for 'reasonable effort'? Is it reasonable effort for example if in 10 days all that is observed is a single juvenile slow-worm? Can it be reasonable to carry on for a further 10 days just in case there is one more? A very interesting topic indeed.

PS we are not quite as bad at catching things as the graph might suggest, this is raw data that includes a number observations of juvenile lizards on ACOs in warm conditions so the same animals appear over and over as observations as opposed to captures - their day will come

I don't recall ENS No.27 addressing mitigation only survey methodology and can find no reference to CTDs briefly looking through the publication.

I don't always think these guidelines are always a good thing; I will be honest about this. I don't think it is good to be told I need to carry out site survey 20 times when I have made as full an assessment as I'm ever likely to in 7 visits just because someone happened to find the Froglife Advice Sheet 10 and decided to quote it without really understanding the content.

These decisions should be left to the consultant i.e. what is 'reasonable survey effort' and what is 'reasonable capture effort'. The real issue here is that more consultants working with reptiles ought to get a handle on the animalÆs basic ecology, perhaps then we won't need arbitrary rules.

(rant over )

PS we got the new peak for our graph at 9 animals for this area all lifestages/Af & Lv - an indication that capture effort is turning the tide but it ain't over yet..

Hi Matt, yes I know what goes on all too well.

I think the more usual approach for reptiles by most consultants is to book x amount of visits. Something between 60 and 80 being the norm. At the end of this time it is usual to regard that appropriate capture effort has been applied, rather than using CTDs.

I would like to hear from a few of our other members who are consultants as to their methods of reaching 'sign off'. My own experiences of working for other consultants in the past showed 'various' approaches.

The M+G policy is to book more than sufficient sessions, if we capture a site out before we complete all of them, so be it we charge the client for the completed sessions and the job is done. Many consultants will take the opposite approach of booking as few as possible when tendering for a contract in hope of getting the work, only then to book more or to run into problems with the number of animals on the site/size of the receptor area/client cost and time.. well you probably know the score!

It interests me a lot as a subject as I strongly believe that adequate initial survey is the key to avoiding all these problems on a site and it should be perfectly within the consultants ability to book an appropriate number of capture sessions based on site complexity/species/relative density etc.

Without being able to reach these conclusions from survey data how on earth can an appropriate receptor area be identified or appropriate capture effort appled? In other words how can the site be effectively mitigated at all?