River Survey 2016

Throughout the summer of 2016, volunteers from the Worcestershire Mammal Group (and beyond) studied Worcestershire’s rivers and brooks for signs of mammals, mostly European otter and American mink. From this, we and the Worcestershire Biological Records Centre (WBRC) received a variety of new records, including almost one hundred otter records! These new records were mostly from signs such as spraints and footprints.

The majority of new otter sightings fell in areas where we already had data for otters, which shows that these original strongholds are still well populated. However, in some cases, records were for brand new locations. Examples of these include otter spraint on the Elmbridge Brook and Elmley Brook near Cutnall Green, a new cluster of records to the east of Kidderminster and spraint found on Swans Brook near Redditch. Whilst many of the records gathered follow the major rivers and larger brooks in the county, it is interesting to note that some fall on minor brooks and small tributaries away from the main water sources. This may show that otters are expanding their range further away from the main rivers and existing hot spots due to an increase in population driving the need to expand into new territories.

We received far fewer mink records, and again these were mostly in the same locations as previous records. There were a few new locations, such as on the Blakedown Brook in Churchill, or areas showing new records further upstream than previous recordings such as in Kidderminster town centre.

This survey work just goes to show the difference that a small group of volunteers can make and the analysis we can get out of that work. Clearly, otters are spreading around the county, which is very exciting. By gathering and comparing records from year to year, we can track expansions like this, and also interactions between species.

It is likely that the lack of mink records was due to the lack of resources needed to cover all the waterways in Worcestershire. However, there is plenty of recent research to suggest that where otters are flourishing, mink are declining. This appears to be due to competition for territories and food, in which the larger otter dominates, rather than otters preying upon mink. It is interesting that the number of mink records submitted to the WBRC has decreased dramatically since the early to mid-2000’s whereas otter records are now commonplace. It will be fascinating to see how this unfolds over the next five to ten years, assuming otters continue to increase in Worcestershire and re-colonise its waterways.

We’d like to thank all who took part in this! Please continue to go out and record using the skills you’ve developed for these surveys, as this will feed into the push to collate mammal data for an update to the Worcestershire Mammal Atlas. Approximately 20% of the county has no mammal records at all. You can see from the map on the Mammal Atlas page of the WBRC website that these sparse areas include the Bishampton/Throckmorton region, the area south of the Malverns and around Middle Littleton in the far south-east of the county. Any mammal records for these blank spots would be gratefully received, as most common species are heavily under-recorded; so get out and enjoy recording Worcestershire’s mammals!

(Huge thanks the WBRC for collating the records and producing this report. Don’t forget to check them out at