Saving England's most threatened species from extinction

What stops growing in the winter?

Luckily the Little Whirlpool Ramshorn Snail is able to withstand freezing conditions and so should have survived the cold snap we had in early December.  They stop growing during the winter months but may start again as the water warms up in the spring to reach their grand size of 4-5 mm diameter!

It’s been a busy few months at RSPB’s Pulborough Brooks reserve, one the snail’s few strongholds and where the Back from the Brink project is working.  It started with the creation of new habitat that can be allowed to develop to suit the snail’s needs. A new ditch and several spurs were dug before the ground conditions got too wet to work.  We didn’t get as much done as we wanted so will be continuing this work next autumn.

Next we tackled the unwelcome carp which had found their way into the ditches, probably from the river when it over-topped its banks.  They burrow into the mud and stir it up, which makes the water very cloudy and unsuitable for the snail.  Little Whirlpool Ramshorn Snails like clear water which warms up quicker than cloudy water. They also need well oxygenated water with submerged plants and these don’t grow in cloudy water as there isn’t enough light. Large numbers of small carp, around 15cm long, and quite a few large carp of over 10lb were caught and rehomed, including several fancy varieties such as Mirror and Koi Carp. Let’s hope this helps the water conditions improve so the snail can colonise more ditches.

Finally we set up the trial of four different methods of ditch management. In each one an area is left un-cleared and full of vegetation to act as a refuge for the snail. In time it is hoped that the snail will recolonise the cleared areas as they become more vegetated.  We’ll be monitoring them over the course of the project to see if one method is better than another.

Carrying out the snail monitoring requires the specialist skills of licenced surveyors but volunteers have been able to help with other aspects of the monitoring. We’re very grateful to Justin, our volunteer intern, who monitored the turbidity or cloudiness of the ditches before the carp were removed. This will need repeating over the next few months along with other ditch measurements.

Looking forward to the New Year!

 

Jane Sears

Project Officer.

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