Surveying for otters Lutra lutra

It’s been a busy few weeks at Oakley Ecology, with the end of seasonal surveys and a move from field work, to focused client engagement and delivery of written assessments.

OLYMPUS DIGITAL CAMERA

This week we want to share with you a typical otter survey. Our otter survey methods follow standard survey methods, developed and published by Paul Chanin, a mammal ecologist who developed the survey methods for the first widespread otter surveys in the UK. His collaborated methods are widely used today by UK ecologists as standardised techniques for searching for and ultimately determining the use of water bodies by otters.

The main objectives to any otter survey are to identify whether otters use a waterbody and, if so, to what extent; whether use be occasional, for commuting or foraging purposes or for more frequent use with resting places present. In order to do this we need to look for evidence and this comes from searching for clues that help to build up an assessment and enables a true reflection on the suitability and functionality of the habitats present. This information can then either be used in population research and assessment or for developing landscape opportunities to encourage the spread of otters, for example, by identifying negative influences to dispersal, such as barriers to movement.

Firstly, through discussion with our clients and information obtained about the nature of the development, we identify the need for an otter survey. This may be because the development directly impacts a waterbody, such as a river, stream, lake or wetland or even because the development is likely to have an indirect impact on otter through increased noise, lighting or vibration during and after construction.

The second stage of the assessment is to determine the use of a waterbody by otters and this follows the standard methods as mentioned above. Surveys are typically completed between May and September, however survey seasons can be extended if weather conditions allow, for example, if there are no heavy periods of rain through October which would remove signs of use, survey could be completed. Surveys are avoided during and directly after any rainfall event as these will remove fields signs.

Maps are produced for the waterbodies affected by the development and will include wider search areas to ensure sufficient information is gathered giving a true interpretation of the results captured. Waterbodies are walked by our experienced ecologists and the following information is recorded:

  • Locations of otter spraints (faeces) – often located on prominent features within the waterbody or on the banks, features like weirs, bridges, rocks, berms or tree roots
  • Location of slides and tracks – slides are formed when otters frequently slip into the water, using the same route. Tracks can be found on in-channel features like berms, sand banks, tree roots as well as on bareground within 10m of the waterbody.
  • Location of otter tarring – where otters mark territory with faeces higher up the bank where prominent features aren’t present.; features include grass, loose earth and rocks.
  • Otter evidence can include urine staining and anal secretions (can be known as otter jelly)
  • Location of any day resting places – worn areas of grass or other vegetation on or close to the bank
  • Location of otter holts or other large entrances along the waterbody.

All information is mapped and a picture forms on the otter use of the waterbody. This information can then be used to determine to what extent the development will impact, if it does at all, on the local otter population.

If you are thinking of developing land close to a waterbody and want to ensure the impacts on otters are assessed appropriately, get in touch with Oakley Ecology, we will pull together a free check of local information for you.