Individual study: Adder Vipera berus hibernacula construction as part of a mitigation scheme, Norfolk, England
Whiting C. & Booth H. (2012) Adder Vipera berus hibernacula construction as part of a mitigation scheme, Norfolk, England. Conservation Evidence, 9, 9-16
A significant adder, Vipera berus, population was identified within the Upper Thurne river catchment during baseline surveys in 2009. An adder bank (hibernacula) was constructed in the autumn 2009 in advance of flood defence works at Horsey in 2010 to mitigate any temporary loss of hibernation and natal den sites. Reptile fencing was erected around the adder banks and some adjacent grazing marshes in February 2010 to create reptile enclosures. During March to May 2010, 119 adders were moved to the adder banks from the flood banks that were then stripped of vegetation and topsoil to discourage animals from re-entering the working corridor. Sections of the adder fencing were removed in mid-May to allow animals to disperse to their summer foraging grounds. Surveys during summer 2010 indicated breeding success within the banks. Pre hibernation surveys in 2010 recorded a peak count of 22 animals, and a spring emergence survey of the adder bank in 2011 identified 17 individual adders. A further four were recorded using an adjacent store of rush, Juncus, bales. Monitoring through summer and autumn 2011 identified a further 16 individual animals on or close to the adder bank, including six gravid adders. Eighteen out of the 33 adders recorded using the adder banks in 2011 were recaptures. Fifteen ‘new’ adders (i.e. not relocated during the 2010 mitigation) were subsequently identified as using the adder banks to hibernate or give birth. The total cost of constructing the adder banks and erecting/dismantling the reptile fencing was £63,500.