Winter Bats
Bats build up their fat reserves in autumn by foraging at locations where insect biomass is readily available in shed loads (such as at riparian sites, standing water, sewage works). They need to sustain themselves for torpor/hibernation over the winter months, when there is little or no food available. Insects generally do not fly (or are less available) when temperatures fall below 10 degrees centigrade (or during and after periods of heavy rain). Optimal winter roosting conditions are the opposite of those sought in the summer. Bats require cold and humid conditions. They hibernate as singles. They are not seeking warmth, but require cold conditions as they do not want to wake up to no food as this would be high cost to their limited energy budget. Bats are very vulnerable in torpor and can take >30mins to wake up and fly. Very little is known as to the whereabouts of our London hibernation sites: some bat species are known to migrate to European caves; or use gree...