Otters (Lutra lutra) are an elusive semi-aquatic species which were once widespread in Great Britain and Europe. In the 1950s and 1960s the populations of otters declined rapidly and drastically. It is thought that the use of pesticides such as DDT and Dieldrin, and pollutants such as PCBs, was very common at this time and this resulted in the population declines.
Thankfully the otter population has increased over the last 25 years and their range has expanded across much of England. Today it is estimated that the population in Great Britain as a whole is 10,300 (Scotland 7,950; England, 1,600; Wales; 750). It is thought that otter population recovery has been most successful in the South West and along the Welsh borders where they had a stronghold during the decline years.
Otters are fully protected in the UK by Schedule 5 of the Wildlife and Countryside Act (1981) as well as the Conservation of Habitats and Species Regulations 2010 (which makes it a European Protected Species). They are protected against killing, injuring, disturbance and their habitat and resting places are also protected. Due to this protection, it is highly important that land owners and developers are aware of the presence of otters, particularly where rivers are present. If otters are thought to be present on your site or in any surrounding areas then surveys need to be carried out by someone who has training and experience.
Surveys for otters can be carried out all year round, but they are most successful in the spring when evidence is usually easier to see as water levels tend to be lower and wet mud is exposed, therefore signs such as tracks may be visible. Spraints (dung) are also definitive evidence of presence and they are usually deposited on prominent places such as rocks and fallen trees in order to mark their territory. A number of other indicators are used as well including feeding remains, otter slides (into the water), holts (underground dens) and couches(above ground sites where otters rest during the day ).
Otter movement varies from season to season meaning that several surveys may need to be carried over the year to establish how big the impact of the project is and what mitigation measures may be necessary.
Otter surveys can take place all year round, although vegetation cover and weather conditions may limit the times the survey can be carried out. Recent heavy rain or floods need to be avoided.
If you think you may have otters on site call Acorn Ecology for advice.