Based on the article “Mammals of the Welsh Harp”, by Andrew Self and Clive Herbert, in Birds of Brent Reservoir
To ascertain the status of the mammals at the reservoir a survey was carried out in 1995 (Herbert). This, along with reports of bat surveys and the personal observations from several regular watchers at the site, has been used to give a brief summary of the mammals of the Welsh Harp.
- Bank Vole Clethrionomys glareolus
This species was recorded from four separate areas in 1995 (Herbert).
- Field Vole Microtus agrestis
The Field Vole is the small rodent most often seen or heard around the reservoir. The large expanses of unmown grassy areas near the dam and by the Northern Marsh, as well as areas like the disused allotments, provide a perfect habitat for these voles. Their abundance also attracts predators such as Kestrels and owls. Indeed, when pellets from over-wintering Long-eared Owls were examined they were found to exclusively contain the remains of this species (A.Self, pers ob).
- Wood Mouse Apodemus sylvaticus
This was the only species trapped in all five transects in the 1995 Mammal Survey (Herbert).
- Common/Brown Rat Rattus norvegicus
Widespread at the reservoir, the Common Rat is most often observed near the bridge on Cool Oak Lane, where it feeds on scraps that visitors have left out for the birds.
- House Mouse Mus musculus
This species was not recorded in the 1995 Mammal Survey because the traps were mainly laid out around the “wilder” areas of the reservoir. But the species is undoubtedly present within the recording area, probably in many of the houses and sheds as well as many of the factories bordering the Eastern Marsh.
- Grey Squirrel Sciurus carolensis
The Grey Squirrel is the most commonly observed mammal at the reservoir, being recorded from all areas of the reservoir from the woodlands to back gardens, where it can regularly be seen raiding bird tables in the winter.
- Mole Talpa europaea
Although it is rarely seen, the mole’s presence is betrayed by the molehills that can be found among the grassy areas around the reservoir, eg at least 10+ fresh hills were located around the perimeter of the sports pitches on Neasden Recreation Ground in 1995 (Herbert). With the occasional finding of a dead mole, these sightings point to it being fairly common, although they are never recorded on the largest expanse of open grassland at the West Hendon Playing Fields which may well be due to the underlying substrate being dumped material unsuitable for burrowing.
- Common Shrew Sorex araneus
Of all of the small mammals at Brent, this species is the most likeliest dead specimen to be found.
- Water Shrew Neomys fodiens
A Water Shrew was seen on 23rd October 1995 by the cycle track in the Northern Marsh (Herbert). It was considered to be in atypical surroundings so its actual status at Brent cannot be confirmed, although it was recorded on the canal behind the dam in the 1960s (per Batten).
- Hedgehog Erinaceus europaeus
A common mammal at the reservoir but rarely noted due to its nocturnal habits. The remains of one that had been eaten by gypsies was found when there was an encampment at the Northern end of the reservoir in the late 1980s (J. Colmans pers ob). Two road casualties were found on Cool Oak Lane on 7th May 1995.
- Whiskered Bat Myotis mystacinus
One old record from Hendon (Fitter) may be within our recording area.
- Daubenton’s Bat Myotis daubentonii
The first record of this species is from September 1937 when a group of 12 was seen, one of which hit a martin species and fell into the water (Fitter). It was not recorded when bat detectors were used on four occasions between 1978 and 1995, but has subsequently been detected on several bat walks.
- Serotine Eptesicus serotinus
This species was recorded for the first time during a bat walk on September 5th 2007.
- Common Noctule Nyctalus noctula
This species was recorded twice during the 1995 Bat Survey. Both appearances were after dark and both individuals left the area quickly so it was considered that they do not roost locally and that the area only constitutes a minor foraging area (Herbert). One was recorded feeding over the open water. Additionally, one was seen flying over the Northern reservoir in the evening of September 8th 1960 with two smaller bats.
- Leisler’s Bat Nyctalus leisleri
This species was unknown at Brent Reservoir in the 20th century, but is now detected during most bat walks.
- Common Pipistrelle Pipistrellus pipistrelus
All individual pipistrelles located in the 1995 Bat Survey were Common Pipistrelle, which were fairly common and widespread around the reservoir. The largest number recorded together was at least eight immediately north of Cool Oak Lane Bridge. No roost sites were found but the appearance of several at dusk around the Field Centre is suggestive of a nearby roost.
- Soprano Pipistrelle Pipistrellus pygmaeus
Since the separation of this species from the Common Pipistrelle in 1999, it has been recorded regularly, but in smaller numbers than Common Pipistrelle.
- Nathusius’ Pipistrelle Pipistrellus nathusii
This species was recorded for the first time during a bat walk on September 5th 2007, when at least two individuals were present. It has since been detected on other bat walks.
- Fox Vulpes vulpes
Foxes are regularly seen around the reservoir, even during the daytime. There are territories in East Marsh, North Marsh and the Field Centre and possibly elsewhere. They have often been seen from the hides as they walk through the reed bed and have been known to take ducks and feral geese as well as Moorhen eggs, although these observations represent just a fraction of their actual diet.
- Stoat Mustela erminea
No longer present at the reservoir, this species was last known to have occurred in the 1960s, although it was only occasionally seen.
- Weasel Mustela nivalis
Like the Stoat, Weasels are no longer reported at Brent although their smaller size could mean that they are still overlooked. The most recent records are from the 1970s when they were not infrequently seen (L. Batten, pers ob).
- Reeve’s Muntjac Muntiacus reevsi
Muntjac have been present at intervals over the past 30 years or so, but none have been reported since 2012.
Creasey P. (1987) Mammals of the Reservoir. London: Welsh Harp Report 1987
Fitter R.S.R. (1949) A Checklist of the Mammals, Reptiles and Amphibia of the London Area: 1900-1949. London: London Naturalist 28: 98-115.
Herbert C. (1995) Bat Survey Report: Brent Reservoir. London: Welsh Harp Conservation Group.
Herbert C. (1995) Small Mammal Survey Report: Brent Reservoir. London: Welsh Harp Conservation Group
Self A., Herbert C. (2001) “Mammals of the Welsh Harp”, in Birds of Brent Reservoir: The Natural History of the Welsh Harp (eds L. Batten, R. Beddard, J. Colmans, A. Self). London: Welsh Harp Conservation Group.