2017 Mammal Report

Mammal report 2017

By John Drewett

Based on the number of records received, Brown Rat must be one of our rarest mammals! This year only four records were received, all of individuals with the exception of an obviously well-established colony in a muck heap near Bainbridge. All but one of the records were in August, when they are more easily seen as they are disturbed by harvesting.
Mole hills were reported from a few locations during the year, but records must represent only a tiny proportion of their true distribution.
Hedgehog continue to be poorly recorded with just three records during the year. Individuals were seen at Low Row and Barningham and breeding was reported from a neighbour's garden in Arrathorne.
Grey Squirrel were recorded at Hackforth and Marfield and a Red Squirrel was at Cotterdale.
There were a number of reports of Brown Hare during the year, mostly from around the Wensley and Middleham areas including 11 seen feeding in a field near Wensley in March. A relatively small number of reports of Rabbit were also received, despite the general abundance of the species in the area. The greatest number counted was 79 in 1 square kilometre at Brompton-on-Swale. As Rabbit are said to be declining in the UK at present, more records would be particularly welcome to enable some monitoring here.
Nine records of Roe Deer were received during the year, all between January and May. Records came from locations near Hackforth, Spennithorne, Wensley and in Colsterdale. As this species lives either alone or in small family groups records were mostly of individuals, the maximum count together being four.
As usual, Common and Soprano Pipistrelle accounted for the majority of bat records during the year, turning up in flight during almost every bat survey. Several small Common Pipistrelle roosts were found, the largest containing ten bats. The continued presence of a maternity roost of Soprano Pipistrelle at the visitor centre at Aysgarth Falls was confirmed.
The behaviour of bats at a roost can be interesting. For example, at one Common Pipistrelle roost at Helwith the bat emerged from the ridge of a single storey outbuilding, before flying along the rear of the adjoining derelict barn and passing through the upper storey north to south, rather than just flying straight off in a southerly direction from its roost. This behaviour was repeated on every visit to the site.
During June several bridges were surveyed, in advance of repair works proposed by North Yorkshire County Council. At Downholme, given the location and surroundings, we expected to find roosts, but only encountered the occasional bat flying past. However, at Grinton we were able to confirm that a maternity roost of Daubenton's bats was still present when we counted out 44 as they left to hunt over the River Swale at dusk.
Natterer's Bat were recorded at eight locations during the year, usually in ones or twos, but a sizeable maternity roost of 80 was found at a barn in the Hunton area in June. A nice record for a species that is very sensitive to light.
2017 was a particularly good year for flying Noctule Bat. A large proportion of 
my survey work over the summer was at locations in Wensleydale and Swaledale and Noctule were seen in flight at most sites, usually just one or two bats passing quickly overhead; no roosts were located.

Brown Long-eared Bat were recorded on 17 occasions during the year in Wensleydale and Swaledale. Some of these were records of bats in flight, but a number of small roosts were located. Except where the animals could be seen within a roof void, this is a very difficult species to track down due to their quiet echolocation calls.

Often, even with years of practice, it is not possible to identify all the bats heard on a bat detector. Recordings are later analysed with computer help, but even theis may not be enough. During the year we therefore note many bats as just 'bat'. Others, in the Myotis genus may be noted as Myotis species, or sometimes a little more precisely as Whiskered / Brandt's. If we really need to know the species (if a roost would be disturbed due to building works, for example) we would then catch the bats under licence to identify them precisely. Consequently, quite a few rather vague bat records are added to the database each year.

Among the more interesting bat records of 2017 we recorded a single passing Nathusius' Pipistrelle flying near Aysgarth Falls in June. Although there are quite a few bat roosts of different species in the vicinity, but this is a relatively rare species and the first Nathusius' record for the area and not known to roost in Wensleydale. It is partially migratory (bats fly in from Scandinavia in autumn), but the timing of the observation suggests that this individual may be resident.

Right at the start of our summer survey season my colleagues and I recorded a single call from a bat during a survey at Redmire. The characteristics of the call were clearly different to those species we usually find, so copies of the echolocation file were sent to other bat experts around the country. Quite quickly three of us agreed that the call was very much like that of a Savi's Pipistrelle, a species generally confined to the Mediterranean, North Africa and the Middle East. This is an extremely rare vagrant to the UK, the only four records being from near the coast in southeast England, Lancashire and Sutherland. Anyone who works with bats will tell you that bat calls vary considerably (even from a single bat) so one call is most definitely NOT enough to provide a record that can be validated. It most likely that if it was a Savi's Pipistrelle it was just passing through, but sadly we will never know.

Badger setts were confirmed in three locations during the year, two in lower Wensleydale and one near Richmond. Two of these were discovered during bat surveys, making the evenings even more interesting. A Badger was also seen running along a road in mid-Wensleydale late one evening.

At the end of July a walker reported an injured Otter on the Ure between West Witton and Wensley, and spraint was found on the Swale at Downholme. Despite few records, Otter are thought to be pretty well established throughout the area.

There were just four reports of Stoat during the year, coincidentally two on the same day, by different observers in different places. The most interesting of the four was a Stoat observed swimming across the River Ure by John Nuttall. No Weasel was reported in 2017.

Only two probable Polecat records this year, one was watched hunting along the roadside at Ballowfields at night on 29th

July, and a large dead animal was reported from Low Lane, Wensley.
There were seven records of Red Fox in Wensleydale and Coverdale, though only two records were of animals seen. The rest of the fox reports were of the distinctive scent left by these animals.

More records are always appreciated and can be sent at any time to ynhsmammals@btinternet.com

Our 2018 Mammal report is published in our 2019 Bulletin, distributed to our members.