Natterer's bats have been found using boxes at two nature reserves
Bat boxes installed across Surrey are now bursting with the mammals, the county's wildlife trust has said.
Species roosting include a rare Bechstein's bat near Ockley, nine Natterer's bats near Dunsfold and a further 12 Natterer's near Elstead.
Surrey Wildlife Trust said the junction of the M25 and A3 dual carriageway was now home to noctule bats, brown long-eared bats and soprano pipistrelles.
Bats first arrived at the sites in 2007 and numbers are growing, experts said.
The wildlife trust is working with the Surrey Bat Group to improve habitats for bats across the county.
Derek Smith from Surrey Bat Group said the reserves at Thundry Meadows, near Elstead, and Fir Tree Copse, near Dunsfold, were the only sites where Natterer's bats had been found using boxes.
Wallis Wood, near Ockley, was the only site in Surrey where the Bechstein's bat had been discovered, he said.