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© 2013 Lizzie Ross BSc MSc

The Otter Network

Research

The Otter Network 2019 Spring Otter Survey
The seventh Annual Spring Otter Survey took place over the weekend of the 27th/28th April 2019 and

once again thanks and congratulations are extended to all the volunteers who took part. Tees Valley Wildlife Trust volunteers also took part again allowing us to continue to monitor the otter population in the Tees Valley. 

The Otter Survey bounced back this year with a new expanded area and more volunteers and survey patches than ever before.  A total of 123 patches of watercourse were surveyed on both days containing 681 sites. Of those 681 sites 281 (41%) were positive for otter signs. A further 18 sites had possible or inconclusive signs. There were 382 sites (56%) which were totally negative. This continues to give us confidence that we are looking in enough places as there are still more sites where there are no otters than sites where we find evidence of otter activity. It is unlikely therefore that we are overlooking many.

There were 82 Day 2 ‘hits’ (fresh signs) which is the highest yet but not surprising given the larger area covered and increased number of volunteers. As usual, many of these ‘hits’ were close together in the same or neighbouring patches and so have been adjudicated to belong to a single territory. The total number of adjudicated territories this year is 47 - again it must be emphasised that this is for a larger survey area. If the territories that were identified in the new areas are taken out then the equivalent number of territories for the previous survey area is 40. This is still an increase and a very positive result.

 

For those unfamiliar with the way the data are analysed it is important to emphasise that we are counting otter territories here not individual animals. It is reasonable to assume therefore that at least some of the adjudicated territories will contain females with cubs meaning the number of actual otters will be greater than the number of territories. However, this really is the only way of getting any kind of numerical data when surveying for otters which are an elusive, wide-ranging, cryptic animal with no individually identifiable markings.

The full report is available as a pdf on the Links and Downloads page.

The 2020 survey will be again be an Otter Network event and will take place over the weekend of 25th/26th April. If anyone reading this would like to take part please contact Vivien through the Contact page of the website.

 

 

Other Research

 

We also try to answer new questions using a mixture of old and new survey techniques.

 

2014 concentrated on mortality on roads in and around Newcastle and if such mortality could be explained.

2012-2013 investigation (Lizzie Ross, Krzysztof Dabrowski, Catherine O'Reilly, Peter Turner, David O'Niell)
 
'A pilot study along 57km of the Tyne to investigate the use of non-invasive DNA technology to aid our understanding of the local otter'
 
Using records of previous otter sightings and signs across the northeast, the area from Newcastle to Hexham (roughly 57km in length) was chosen due to the high density of signs in these areas and the vast diversity of environments due to the combination of a large river and many tributaries in both urban and rural areas. Spraint (faeces) collection took place between February and March 2013 and samples were taken to the Waterford Institute of Technology in Ireland as they are pioneers in the field of such DNA studies.
   
Where is the best place to find otter spraint?
 
26.5% of samples were found on the main River Tyne but on tributaries and small streams 73.5% of spraints were found. This is likely to  be because smaller tributaries are easier to study and therefore investigations wanting to collect spraint quickly and in abundance should be weighted towards smaller watercourses (dependent on the overall outcomes of the investigation).
 
Do otters avoid pollution and human disturbance?
 
We did not measure pollution within the water during this study, however, spraint densities were unexpectedly abundant in highly disturbed areas, closely followed by low disturbance and finally medium disturbance at considerably lower densities. 
 
What do we know about number of otters within the study area?
 
From 166 positive otter samples, 82 were suitable for sex typing. From this, 38 produced gender specific results with an equal split of male and female samples. Only genotyping can be used to identify individual animals. Of the 38 gender confirmed samples, only 21 were suitable for genotyping. From those analysed, only 5 samples were typed successfully with no recaptures. These were 3 females and 2 males. The DNA quality was not sufficent to assess relationships between animals.
Applying average territory sizes to male and female DNA records, it is suggested that there is minimum of 13 animals along this stretch. 
What is the density of otters on the Tyne?
 
Our estimate through this study is 0.22 otters per kilometre of the Tyne 
 
Are there otters in Newcastle?
 
We have evidence of two-three males which appear resident and a single female. Further studies will tell us more.
 
What can I do to help?
 
Send us your records
 
Help us collect data
 
Donate funding - each spraint costs around £15 from collection to genotyping