Background information and definitions
The natterjack toad Bufo calamita has declined, particularly in the UK where the species is now endangered. The decline is largely due to habitat destruction and the acidification of breeding sites. In Britain, attempts to reintroduce the species to sites where they had recently gone extinct started in the 1970s.
Supporting evidence from individual studies
A replicated, before-and-after study in 1972–1995 at dune and heathland sites in England, UK (Denton et al. 1997) found that at least six translocations of natterjack toad Bufo calamita eggs resulted in expanding new populations and eight showed initial signs of success. Two of three dune sites had breeding within three years and the third (> 5 years old) established one of the largest populations. Five of 17 translocations on heathland were successful, with stable or increasing adult numbers and breeding for at least five years. Six less than three years old, all produced toadlets in their first year. Six failed (five pre-1980) with no successful metamorphosis. Ten successful translocations were to sites with new ponds, in heathland six were concrete and one butyl plastic lined. Nine were undertaken after 1991 and comprised translocations of eggs (two spawn strings, i.e. 5,000 eggs) each year for two years. Scrub clearance was undertaken at two dune and seven heath sites. One heath site had limestone added to acidic ponds. Low-density sheep or cattle grazing (<1 animal/3 ha) was established at one dune and two heath sites. Spawn strings were counted and toadlet production estimated.Study and other actions tested
A replicated, before-and-after study in 2000–2004 of 13 coastal meadows in Estonia (Rannap 2004) found that translocated natterjack toad Bufo calamita tadpoles bred at at least one site within three years. Following translocation of tadpoles in 2000, the first calling males were heard and spawning was recorded in the spring of 2003 in Saastna. In 2001–2004, terrestrial and aquatic habitats were restored on 13 coastal meadows where natterjacks had disappeared but could be reintroduced. Approximately 30,000 tadpoles from isolated quarry populations were translocated to the restored meadows.Study and other actions tested
A review of 29 translocation programmes for the natterjack toad Bufo calamita in the UK (Griffiths, McGrath & Buckley 2010) found that 19 of 27 translocations (70%) that could be assessed were successful in the short to medium term, with adults returning to breed successfully and self-sustaining populations established at some sites. Re-establishing toads on dune or saltmarshes was more successful than on heathland (85 vs 57% success). Translocations have resulted in populations of over 200 adults at some sites, although at other sites populations have remained small. The 10 translocations since 2000 have resulted in an increase of known natterjack sites from about 40 in 1970 to 69 in 2010. Between 1975 and 2010, toads were translocated to 29 sites. Reintroductions were mainly through translocation of eggs and tadpoles from existing populations. In some cases, head-starting of tadpoles and captive breeding was also undertaken. Habitat management has also been undertaken at some sites. Since 1985 all populations have been monitored annually.Study and other actions tested
A replicated, before-and-after study in 1985–2006 of natterjack toad Bufo calamita populations at 20 sites in the UK (McGrath & Lorenzen 2010) found that populations increased at sites established via translocations. The average population trend for translocation sites was significantly positive (0.10) while that for native sites did not differ significantly from zero (−0.04). Numbers of years of translocations of wild (including head-started) animals, but not captive-bred animals had a significant effect on population trends. Overall, five of the 20 sites showed positive population trends, five showed negative trends and 10 trends were not significantly different from zero. Data on populations (egg string counts) and management activities over 11–21 years were obtained from the Natterjack Toad Site Register. Translocations were undertaken at seven sites using wild-sourced (including head-starting) or captive-bred toads. Habitat management for toads was also undertaken at seven of the 20 sites.Study and other actions tested
A before-and-after study in 2001 in northern France (Beebee et al. 2012) found that a breeding population of natterjack toads Bufo calamita was established following translocation of adults and juveniles. Annual survival was 25%, which was half the value estimated in native populations. However, there was repeated breeding over several years. In 2001, a total of 5,000 adult and juvenile toads were translocated from a development site to three receptor sites where natterjacks were still or were historically present. Toads were captured using 5 km of drift-fencing with pitfall traps and 160 plywood or carpet boards laid over a 400 ha area. Monitoring was undertaken annually by surveying potential breeding sites and radio-tracking adults.Study and other actions tested