Individual study: Conservation at home: recovery programme for the agile frog Rana dalmatina in Jersey
Gibson R.C. & Freeman M. (1997) Conservation at home: recovery programme for the agile frog Rana dalmatina in Jersey. Dodo, 33, 91-104
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
A replicated, before-and-after study in 1987–1997 in Jersey, UK (Gibson & Freeman 1997) found that agile frog Rana dalmatina breeding populations were established from translocated eggs. Translocated eggs hatched and were successfully reared at all three sites. Populations started breeding within two to three years of release and then bred most years. In 1987, six egg masses were removed from a polluted pond and translocated to a garden pond (1 m2). In 1993, two enclosures in a second pond were stocked with translocated eggs. Surviving frogs were translocated to a third pond in 1994.
Release captive-bred frogs
A replicated, before-and-after study in 1994–1997 in Jersey, UK (Gibson & Freeman 1997) found that there was limited breeding by released captive-bred agile frogs Rana dalmatina. The first egg mass was recorded two years after the first release and eggs were head-started due to the risk of predation by palmate newts Triturus helveticus. However, there was no breeding at the site the following year, although adults were recorded. In 1994–1996, 100–200 well-developed tadpoles each year and in 1996 twenty young frogs were released into two ponds.
Captive breeding frogs
A replicated study in 1993–1997 of captive agile frogs Rana dalmatina in Jersey, UK (Gibson & Freeman 1997) found that frogs bred successfully in one of two captive populations. Breeding occurred at the Jersey Wildlife Preservation Trust in 1994, 1995 and 1997. However, breeding did not occur in the first two years within the five enclosures at the second site. In 1993, three males, two females and 17 juveniles and in 1994 an additional eight juveniles were acquired and housed in a landscaped enclosure with a pond (20 m2). In 1995, an additional five enclosures (3 x 3–7 m) were built on private land and stocked with captive-bred tadpoles and young frogs.
Head-start amphibians for release
A before-and-after study in 1987–1994 of ponds on Jersey, UK (Gibson & Freeman 1997) found that releasing head-started agile frogs Rana dalmatina did not prevent a decline in breeding within the population. Over 300 head-started toadlets were released. However, frog activity at the release site decreased over the years and there was no breeding in 1991 or 1994. In 1987–1989 and 1992, eggs were collected in the wild, reared to froglets and released back in the wild.