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New Forest Pine Marten survey: methodology & techniques

Updated: Aug 9, 2021

Marcus writes:

It has been great to see so much interest in the current Pine Marten fieldwork that we are carrying out together with our partners at Forestry England and HIWWT. We have had quite a few queries about the fieldwork element of the survey, so I thought I would summarise the techniques we have been using in this short blog.


Trail camera screen grab from footage recorded in the New Forest, 31 May 2021


Research

I have enjoyed watching Pine Martens on several occasions, mainly in the Scottish Highlands, and we were also fortunate enough to record them on our trail cameras in the New Forest in 2016 while conducting Hawfinch fieldwork. However, before fieldwork commenced, I still wanted to do as much research as possible into the species to better understand their behaviour and habitat requirements. This involved reading numerous research papers from across the UK and Europe and digesting as much published material as I could find, including the excellent book ‘Pine Martens’ by Johnny Birks. I also talked to other Pine Marten fieldworkers in the UK, including our very own resident Pine Marten expert, Martin Noble. This research element of any survey is vitally important as it helps one get into the head of the target species, and in this case better understand how Pine Martens might move through and work the habitat locally.


Methodology

The primary aim of this first phase of the project was to get a better understanding of the distribution and number of Pine Martens in the New Forest. After discussion with the project team, it was agreed that the initial focus would be on deployment of trail cameras backed up with nocturnal thermal imaging transects. The overall plan is to cover the New Forest systematically over several years, intensively surveying discrete areas for roughly one month at a time; in this first field season we have covered four areas.


Trail cameras

Appropriate placement of trail cameras is vital; each area was therefore fully surveyed prior to deployment to get a feel for areas of suitable habitat and likely Pine Marten transit routes. A lot of time was spent analysing the habitat to ensure that cameras were placed in a broad spread of locations in any given area, while also reading the ground to ensure we were placing cameras in optimal locations. These are either natural bottlenecks that might concentrate any animals in transit, clear well-used transit routes, or areas that are likely to attract foraging Pine Marten.


We did initially trial a range of lures, however, we found these to be ineffective and could potentially attract species such as Fox that could deter Pine Marten. In addition, the use of lures could also skew results - we wanted to ensure we recorded Pine Marten in areas where they occur naturally, rather than potentially attracting animals in from outside. Each camera was checked around one week after deployment so footage could be reviewed to ensure the placement and angle of the camera was correct and that the camera was working correctly (vegetation can cause the camera to trigger and/or the angle of the sun can impact quality). Thereafter, memory cards were switched at regular intervals until the camera was recovered at the end of the survey period. All cameras generated footage, with anything from 30 to over 200 clips of 20-second duration recorded on each camera.


All cameras are placed under permit and in liaison with Forestry England.


A couple of previously unpublished clips of Pine Marten captured during the survey can be found via the links below:



Thermal Imaging surveys

As a control for the trail camera footage, a transect route was established through the core of each survey area with eight viewing points. The transect route is walked once per week after dark, stopping and scanning with a thermal imaging camera for a few minutes at each transect point. No artificial light is used, so the transect route largely kept to marked trails to aid nocturnal navigation.


Data collection and analysis

All mammals recorded on the trail cameras are documented on a master database - to date around 7000 records of 14 species of mammal have been recorded. This data supports the survey in many ways and gives fascinating insight into the range and density of mammal species active in the New Forest across different areas.


In addition, several interesting bird species have been recorded on the cameras, including numerous hunting Goshawks, Buzzards and Tawny Owls, as well as Lesser Spotted Woodpecker, Nightjar, Hawfinch, Woodcock and even two records of Kingfisher!

Overall, since survey work started in early March, I have logged over 600 hours (roughly 80 days) on the project through a combination of fieldwork, reviewing and documenting footage, and data analysis. We have a lot more work to do over the coming months, but it has been a pleasure to work on this challenging yet charismatic and wholly endearing species, and to get a small insight into their world.


Next Steps

We are at the very early stages of this collaborative project. Survey work will continue over the next few years as we build a better understanding of numbers, distribution, habitat use and integrity of the Pine Marten population in the New Forest. The systematic survey will continue for at least one further season, while the survey will continue beyond, the nature of ongoing fieldwork will be influenced by our findings over the next field season.


We will aim to share further updates via this channel, including additional footage of Pine Martens and some of the other interesting species that have been recorded.

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