Action: Create ponds for frogs
- Three of five before-and-after studies (including one replicated study) in Australia, Spain, the UK and USA found that translocated, head-started, captive-bred and naturally colonizing frogs established breeding populations in created ponds. Two found that breeding populations were established at one of four sites by translocated frogs, but were not established by captive-bred frogs. One replicated, before-and-after study in Denmark found that frogs colonized created ponds. One before-and-after study in the Netherlands found that pond creation, along with vegetation clearance, increased a breeding population of European tree frogs.
- An additional three of four replicated, before-and-after studies in Italy, the UK and USA found that naturally colonizing frog species reproduced in 50–75% of created ponds. Two found that translocated frog species reproduced in only 31% of created ponds, or colonized but did not reproduce successfully. One replicated study in the USA found that survival of translocated Oregon spotted frogs increased with increasing age of created ponds.
Supporting evidence from individual studies
A replicated before-and-after study in 1983–1993 of eight created ponds in a Country Park on restored farmland in England, UK (Williams & Green 1993) found that common frogs Rana temporaria colonized and reproduced in six of the ponds (see also Williams 2005). By 1992, a total of 195 egg clumps were counted (1–70/pond). Numbers declined to 123 egg clumps in 1993 (0–32/pond), which was considered to be due to drought. Ponds of 4–625 m2 were created in 1983–1987. Twenty ponds were also restored in the area increasing the total pond area from 2,248 m2 in 1983 to 4,965 m2 in 1993. Egg clumps were counted, as an index of numbers of breeding females, in created ponds in February–March.
A before-and-after study in 1986–1993 of 13 created ponds in a marsh reserve in Peterborough, England, UK (Cooke & Oldham 1995) found that translocation resulted in breeding populations of common frog Rana temporaria. Froglets emerged in 1986 and 1987 and the first naturally laid eggs were recorded in 1988 for frogs (peak in 1989: 162 clumps). Up to 16–39% of eggs were lost to desiccation each year. In 1985, 13 ponds were excavated. Local frog eggs were introduced to the ponds in spring 1986 (200 clumps), 1987 (150), 1990 (8), 1991 (4) and 1993 (14). Adults and eggs were monitored 1–3 times/week in spring 1986–1993.
A replicated, before-and-after study in 1991–1994 of nine created ponds on the island of Lolland, Denmark (Hels & Fog 1995) found that European tree frogs Hyla arborea colonized three of the ponds by 1994. Those colonized were within 500 m of densely populated ponds. The ponds were dug in 1991–1993. Frogs were monitored by call surveys and dip-netting each year.
A before-and-after study in 1974–1995 of seven created forest ponds in Missouri, USA (Sexton et al.1998) found that one of four translocations of wood frogs Rana sylvatica established breeding populations in five ponds. The successful translocation resulted in a stable population between 1987 (311 captured) and 1995 (364). Wood frogs also colonized four additional created ponds (0.9–2.4 km). In 1980, 11 wood frog egg masses were translocated 50 km into four created ponds. Monitoring was undertaken using drift-fencing with pitfall traps around ponds and by egg mass counts and call surveys.
A small, replicated, before-and-after study in 1995–2000 of two created ponds in agricultural land and a reserve in Ohio, USA (Weyrauch & Amon 2002) found that translocated gray tree frogs Hyla versicolor did not reproduced in created ponds. Gray tree frogs were heard calling at one pond in 2000, but no evidence of breeding was found. Green frogs Rana clamitans, northern leopard frogs Rana pipiens and American toads Bufo americanus colonized both and bred in one pond. Ponds were created in 1995–1997 and were 2–4 m deep. Water, vegetation, plankton and organic matter (from local wetlands) were added. Larvae (0–35) and metamorphs (0–4) were added in spring 1996–1998 and 2000. Amphibians were monitored drift-fencing and pitfall traps around ponds and by dip-netting and egg counts.
A replicated, before-and-after study in 1998–2003 of 13 created and one restored pond in Gipuzkoa province, Spain (Rubio & Etxezarreta 2003) found that translocated adult and released head-started and captive-bred juvenile stripeless tree frogs Hyla meridionalis established breeding populations in 11 ponds. Translocated adults survived in good numbers and returned to 12 ponds. Mating, eggs and well-developed larvae were observed in 11 ponds and froglets were recorded in some ponds. However, introduced predators, dense vegetation, eutrophication and drying resulted in reduced survival and reproduction in some ponds. In 1999–2000, 13 ponds were created, one restored and vegetation was planted. In 1998–2003, a total of 1,405 adults were translocated to the ponds. Eggs were collected and reared in captivity (outdoor ponds) and released as 871 metamorphs and 19,478 tadpoles into eight ponds. An additional 5,767 captive-bred tadpoles were released.
A continuation of a previous study (Williams & Green 1993), in this case combining data from 31 ponds in a grass and woodland park in 1983–2004 (Williams 2005), found that pond creation and restoration significantly increased reproduction by common frog Rana temporaria. Numbers of egg masses increased from 40 in 1983 to 1,852 in 2002, but then declined to 1,000 in 2004. Numbers of egg clumps increased with pond size and eight ponds contained 89% of the egg masses. The numbers of ponds used for breeding each year increased from one in 1983 to 20 in 2000. Breeding tended to occur two years after pond creation or restoration. Eggs, tadpoles and frogs were introduced and removed from ponds by the public, particularly in 1984. Colonization may not therefore have been natural.
A replicated study in 2001–2004 in four created ponds within a wetland in Oregon, USA (Chelgren et al. 2008) found that survival of translocated Oregon spotted frogs Rana pretiosa increased with increasing pond age. Nine ponds were created in 2001–2004 using explosives (0.01–0.07 ha; 2 m deep). In spring 2001, nine spotted frog egg masses and in June–September 2001, 41 frogs were translocated to the four largest ponds from a site 2.5 km away. Frogs were tagged.
A replicated, before-and-after, site comparison study in 1999–2006 of 13 created ponds in woodland, wetlands and agricultural land in Lombardy, Northern Italy (Pellitteri-Rosa et al. 2008) found that translocated Italian agile frog Rana latastei tadpoles reproduced in four of 13 created ponds. At least one egg mass (1–14) and/or more than one adult calling male (4–8 in two ponds) were recorded in four of 13 created and two of five existing unmanaged ponds; the difference was not statistically significant. Up to four adults were found in three of the ponds. Human disturbance and predator presence had a negative effect and woodland, shore incline and pond permanence a positive effect on success. Ponds were excavated in six Natural Parks in 1999–2001. In 2000 and 2001, tadpoles were released in 13 created and five existing unmanaged ponds, which had not recently been used for breeding. Ponds were monitored by visual, torch and call surveys from February to April 2006 during 45 field surveys (average 2.5/pond).
A before-and-after study in 2004–2006 of three created ponds in wetlands in New South Wales, Australia (Stockwell et al. 2008) found that captive-bred green and golden bell frog Litoria aurea released as tadpoles did not establish a stable population because of death from chytridiomycosis. Tadpole survival was high following release and some metamorphs survived for up to a year. However, numbers declined over the following 13 months and no frogs were recorded from March 2006. Four of six dead frogs found in 2005 and 53% of 60 juveniles captured tested positive for chytridiomycosis. In 2005, 850 tadpoles were released into three ponds created in 2002 within a restored wetland. A fence was installed surrounding the ponds and grassland (2,700 m2) to contain the frogs and to attempt to exclude competing species, predators and the chytrid fungus. Visual encounter surveys were carried out two to four times each month. A sample of frogs were captured and tested for chytrid fungus.
A before-and-after study in 1999–2004 of two created ponds in Arncliffe, near Sydney, Australia (White & Pyke 2008) found that a stable population of green and golden bell frogs Litoria aurea was established from released captive-bred, translocated and colonizing individuals. By January 2000, five non-translocated frogs had colonized the ponds. In March 2000, eight adults, eggs, metamorphs and 20 juveniles were recorded, along with other species. The following spring, 14 adults, including 10 first year adults, were recorded in the ponds. The population was estimated at over 50 adults by 2004. Two ponds (25 x 20 m) were created as mitigation for development in 1999. Three frogs were translocated 150 m from the development site to the new ponds in early 2000. Fifty tadpoles were released into the ponds in March 2000 and 150 in February 2001. Frogs were monitored at night
A before-and-after study in 1978–2011 of 10 created ponds within a nature reserve on historic clay pits and farmland in Limburg, the Netherlands (van Buggenum & Vergoossen 2012) found that pond creation, along with vegetation clearance, increased the breeding population of European tree frogs Hyla arborea. Numbers of males increased from 50 to 150–400. Numbers increased with increasing pond area. Ponds (100–450 m2) were created in 1983, 1985 and 1993. Vegetation removal was also undertaken. Calling males were surveyed two to four times in April–May each year.
- Williams L.R. & Green M. (1993) Pond restoration and common frog populations at Fryent Country Park, Middlesex, 1983-1993. London Naturalist, 72, 15-24
- Cooke A.S. & Oldham R.S. (1995) Establishment of populations of the common frog Rana temporaria and common toad Bufo bufo in a newly created reserve following translocation. Herpetological Journal, 5, 173-180
- Hels T. & Fog K. (1995) Does it help to restore ponds? A case of the tree frog (Hyla arborea). Memoranda Societatis pro Fauna et Flora Fennica, 71, 93-95
- Sexton O.J., Phillips C.A., Bergman T.J., Wattenberg E.W. & Preston R.E. (1998) Abandon not hope: status of repatriated populations of spotted salamanders and wood frogs at the Tyson Research Center, St.Louis County, Mo 1998. Pages 340-344 in: Status and Conservation of Midwestern Amphibians. Iowa City, Iowa.
- Weyrauch S.L. & Amon J.P. (2002) Relocation of amphibians to created seasonal ponds in southwestern Ohio. Ecological Restoration, 20, 31-36
- Rubio X. & Etxezarreta J. (2003) Plan de reintroducción y seguimiento de la ranita meridional (Hyla meridionalis) en Mendizorrotz (Gipuzkoa, País Vasco) (1998-2003). Munibe, 16, 160-177
- Williams L.R. (2005) Restoration of ponds in a landscape and changes in common frog (Rana temporaria) populations, 1983-2005. Herpetological Bulletin, 94, 22-29
- Chelgren N.D., Pearl C.A., Adams M.J. & Bowerman J. (2008) Demography and movement in a relocated population of Oregon spotted frogs (Rana pretiosa): influence of season and gender. Copeia, 2008, 742-751
- Pellitteri-Rosa D., Gentilli A., Sacchi R., Scali S., Pupin F., Razzetti E., Bernini F. & Fasola M. (2008) Factors affecting repatriation success of the endangered Italian agile frog (Rana latastei). Amphibia-Reptilia, 29, 235-244
- Stockwell M.P., Clulow S., Clulow J. & Mahony M. (2008) The impact of the amphibian chytrid fungus Batrachochytrium dendrobatidis on a green and golden bell frog Litoria aurea reintroduction program at the Hunter Wetlands Centre Australia in the Hunter region of NSW. Australian Zoologist, 34, 379-386
- White A.W. & Pyke G.H. (2008) Frogs on the hop: translocations of green and golden bell frogs Litoria aurea in Greater Sydney. Australian Zoologist, 34, 249-260
- van Buggenum H.J.M. & Vergoossen W.G. (2012) Habitat management and global warming positively affect long-term (1987-2011) chorus counts in a population of the European tree frog (Hyla arborea). Herpetological Journal, 22, 163-171