Conservation of New Zealand lizards (Lacertilia : Scincidae) by translocation of small populations

The successful removal of rodents from islands around New Zealand has enabl ed translocation of rare species of lizards to new sites within their forme r range. Four species of skinks were translocated to Korapuki Island, Mercu ry Islands, New Zealand: Cyclodina alani, C. oliveri, C. whitakeri and Olig osoma suteri. Responses of three of the lizard species to release were pred icted using a deterministic population model then compared with the actual performance of wild populations. The population models predicted that if po pulations of about 30 C. whitakeri and O. suteri were released, C. whitaker i would be increasing by 7% p.a. and O. suteri would be increasing by over 35% p.a, during year five. If 20 C. alani were released, the population cou ld be increasing by 70% p.a. during year five. Population expansions are be ing recorded for all three species, but observed population increases were lower than those predicted for two species, partly because of low catchabil ity of immature lizards. The lowest rate of increase (up to 7% p.a.) was fo r C. whitakeri. Low rates of population expansion found in species such as C. whitakeri raise a conundrum: the rarer a species is, and the lower its a nnual reproductive output, the larger the number of individuals that may be required for translocations to succeed. Translocations may be regarded as successful when new populations are self-sustaining and comprised only of l ocally born animals. Despite the populations increasing, it may not be poss ible to claim success far the three intensively studied species on Korapuki Island until at least 20 years after release. This is because of longevity of the founders, which are still being caught up to 12 years after release . Extreme longevity, and hence prolonged post-release monitoring, is likely to be a recurrent problem for translocations of rare lizards. O 2001 Elsev ier Science Ltd. All rights reserved.