Monday, 18 June 2012

Daubenton's Bat Maternity Colony

Batty Boat Trip 2012
Over the past 8 years, the London Bat Group Batty Boat Trip has provided time series data, of the bat activity along stretches of the river at Hampton Wick, Kingston, Surbiton and Thames Ditton (see Bat Pages for a species list, right hand tabs). It is one of the annual monitoring visits studying the bats at the Seething Wells Filter Beds. This year there has been concern at the change in activity at the site. We failed to see any Daubenton's bats during their emergence period. A subsequent visit in perfect weather conditions ( 8/8 cloud cover, 16 degrees, no wind,17.6.12) noted that animal numbers and the pattern of activity has changed significantly. Animal numbers are reduced and the bats had no urgency to emerge as per adults with young to feed. The light sampling behaviour normally observed, was not apparent to the same degree as in previous years.

When bats have young, the adults need to forage close-by, as they must return to feed their pups (milk). When the weather is bad or there is a prevailing south-westerly wind creating movement on the water surface, the adults become dependent on the filter-beds, they must forage over calm water.Their optimal habitat is Standing Water, a National Priority Habitat. This information sheet states that this species has an affinity to waterworks www.bats.org.uk/publications daubentons_bat

In the London region, we have evidence of only 4 maternity colonies of this species, within the last five years. As stated Daubenton’s bats have a known interest in waterworks sites, due to their requirements for high humidity and their need to have a range of roost opportunities. The males do not roost with the maternity colony and roost elsewhere, although they remain close by (to keep an eye on the females).

Vanity lighting nearby, note the travel across the water
The environment around the roost is fast changing. The Filter Beds have been drained and no longer provide open water foraging areas with emergent vegetation breaking the water surface. Light pollution is also increasing at this site and Daubenton's bats are a very light shy species. see also Benton the bat or a radio interview about more general topics
Biodiversity of Seething Wells

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