Collected Evidence: Collected Evidence: Install barrier fencing along roads Seven of eight studies (including one replicated and two controlled studies) in Germany, Canada and the USA found that barrier fencing with culverts decreased amphibian road deaths, or decreased deaths provided that the fence length and material were effective. One found that low numbers of amphibians were diverted by barriers during breeding migrations. One replicated study in the USA found that barriers at least 0.6 m high were required to prevent green frogs and leopard frogs climbing over. Two studies in the Netherlands and USA found that treefrogs and 10% of common toads climbed over barrier fencing during breeding migrations. Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F756https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F756Wed, 14 Aug 2013 11:23:38 +0100Collected Evidence: Collected Evidence: Remove tree canopy to reduce pond shading One before-and-after study in Denmark found that translocated garlic toads established breeding populations following pond restoration that included canopy removal. One before-and-after study in the USA found that canopy removal did not increase hatching success of spotted salamanders.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F758https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F758Wed, 14 Aug 2013 14:36:22 +0100Collected Evidence: Collected Evidence: Create artificial hibernacula or aestivation sites One replicated, before-and-after study in the UK found that providing artificial hibernacula, along with other terrestrial habitat management, maintained populations of great crested newts. One replicated study in the UK found that created hibernacula were used by common frog and smooth newts, but not great crested newts. One replicated study in the UK found four amphibian species close to hibernacula at two of three sites.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F759https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F759Wed, 14 Aug 2013 15:19:25 +0100Collected Evidence: Collected Evidence: Modify gully pots and kerbs One before-and-after study in the UK found that moving gully pots 10 cm away from the kerb decreased the number of great crested newts that fell in by 80%.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F782https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F782Thu, 22 Aug 2013 13:45:55 +0100Collected Evidence: Collected Evidence: Use humans to assist migrating amphibians across roads Two studies (including one replicated study) in Italy and the UK found that despite assisting toads across roads during breeding migrations, 64–70% of populations declined over 6–10 years. One study in the UK  found that despite assisting toads across roads during breeding migrations, at 7% of sites over 500 toads were still killed on roads. Five studies in Germany, the UK and Italy found that large numbers of amphibians were moved across roads by patrols. Numbers ranged from 7,532 toads moved before and after breeding to half a million moved during breeding migrations annually. In the UK, there were over 400 patrols and 71 patrols spent an average of 90 person-hours moving toads and had been active for up to 10 years.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F784https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F784Thu, 22 Aug 2013 13:52:12 +0100Collected Evidence: Collected Evidence: Deepen, de-silt or re-profile ponds Two before-and-after studies in France and Denmark found that pond deepening and enlarging or re-profiling resulted in the establishment of a breeding population of great crested newts or translocated garlic toads. Two studies (including one replicated, controlled study) in the UK and Denmark found that pond deepening and enlarging or dredging increased a population of common frogs or numbers of calling male tree frogs. Four before-and-after studies in Denmark and the UK found that pond deepening, along with other interventions, maintained newt populations and increased populations of European fire-bellied toads or natterjack toads.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F817https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F817Fri, 23 Aug 2013 09:03:23 +0100Collected Evidence: Collected Evidence: Restore habitat connectivity One before-and-after study in Italy found that restoring connectivity between two wetlands by raising a road on a viaduct, significantly decreased deaths of migrating amphibians.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F840https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F840Thu, 29 Aug 2013 15:48:56 +0100Collected Evidence: Collected Evidence: Use signage to warn motorists One study in the UK found that despite warning signs and human assistance, over 500 toads were killed on some roads.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F841https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F841Thu, 29 Aug 2013 15:56:32 +0100Collected Evidence: Collected Evidence: Close roads during seasonal amphibian migration Two studies (including one replicated study) in Germany found that large numbers of amphibians were protected from death during breeding migrations at road closure sites and at road closure sites with assisted crossings and barrier fences.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F842https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F842Thu, 29 Aug 2013 15:58:22 +0100Collected Evidence: Collected Evidence: Translocate toads Two of four studies (including two replicated studies) in Denmark, Germany, the UK and USA found that translocating eggs and/or adults established common toad breeding populations. One found populations of garlic toads established at two of four sites. One found that breeding populations of boreal toads were not established. One before-and-after study in Denmark found that translocating green toad eggs to existing populations, along with aquatic and terrestrial habitat management, increased population numbers. Three studies (including one before-and-after study) in Germany, Italy and the USA found that 33–100% of translocated adult toads reproduced, 19% survived up to six years or some metamorphs survived over winter. One replicated study in South Africa found that translocated Cape platanna metamorphs survived up to 23 years at one of four sites.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F855https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F855Fri, 06 Sep 2013 12:17:03 +0100Collected Evidence: Collected Evidence: Create ponds for toads Four before-and-after studies (including one replicated study) in Germany, the UK and USA found that translocated and naturally colonizing toads established breeding populations in created ponds, or in one case 33% of created ponds. Two before-and-after studies (including one replicated study) in Denmark and Switzerland found that common toads and midwife toads naturally colonized 29–100% of created ponds, whereas captive-bred garlic toads did not colonize. One before-and-after study in Denmark found that creating and restoring ponds, along with head-starting, increased populations of European fire-bellied toads. One replicated, before-and-after study in Switzerland found that midwife toads reproduced in 16% of created ponds.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F868https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F868Wed, 11 Sep 2013 08:55:34 +0100Collected Evidence: Collected Evidence: Create ponds for amphibians Twenty-eight studies investigated the colonization of created ponds by amphibians in general (rather than by targeted species, which are discussed below). All of the studies found that amphibians used some or all created ponds. Nine site comparison studies (including seven replicated studies) in Australia, Canada, Spain, the UK and USA compared amphibian numbers in created and natural ponds. Five found that numbers of species or breeding species were similar or higher in created ponds, and numbers of ponds colonized were similar. Four found that species composition differed, and comparisons between abundance of individual species, juvenile productivity and size at metamorphosis differed depending on species. One found that numbers of species were similar or lower depending on the permanence of created water bodies. One found that populations in created ponds were less stable. One review and two replicated, before-and-after studies in Denmark and the USA found that amphibians established stable populations in 50–100% of created ponds. Six replicated studies (including one randomized study) in France, the Netherlands, UK and USA found that amphibians used 64–100% and reproduced in 64–68% of created ponds, or used 8–100% and reproduced in 2–62% depending on species. One review and 15 studies (including 12 replicated studies, one of which was randomized) in Europe and the USA found that created ponds were used or colonized by up to 15 naturally colonizing species, up to 10 species that reproduced, as well as by captive-bred amphibians. Five replicated studies (including three site comparison studies) in Denmark, Estonia, France, Italy and the USA found that pond creation, and restoration in three cases, maintained and increased amphibian populations or increased numbers of species. Seven studies (including one review) in Austria, Denmark, Poland, the Netherlands and USA found that use or colonization of or reproductive success in created ponds was affected by pond age, permanence, vegetation cover, surrounding landscape, distance to existing ponds and presence of fish.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F869https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F869Wed, 11 Sep 2013 09:16:41 +0100Collected Evidence: Collected Evidence: Create wetland Fifteen studies investigated the effectiveness of creating wetlands for amphibians. Five site comparison studies (including four replicated studies) in the USA compared created to natural wetlands and found that created wetlands had similar numbers of amphibian species, amphibian abundance or communities depending on depth as natural wetlands. Two of the studies found that created wetlands had fewer amphibian species or lower abundance and different communities compared to natural wetlands. One site comparison study in the USA found that created wetlands had similar numbers of species to adjacent forest. One global review and two site comparison studies (including one replicated study) in the USA combined created and restored wetlands and compared them to natural wetlands and found that numbers of amphibian species and abundance was higher or similar, or higher in 54% of studies and similar in 35% of studies reviewed compared to natural wetlands. Three site comparison studies (including one replicated study) in the USA found that certain amphibian species were only found in created or natural wetlands. One before-and-after study in Australia found that captive-bred green and golden bell frog tadpoles released into a created wetland did not establish a self-sustaining population. Five studies (including two replicated studies) in Kenya and the USA that investigated colonization of created wetlands found that four to 15 amphibian species used or colonized the wetlands. One global review and three studies (including two replicated studies) in the USA found that numbers of amphibian species and amphibian abundance in created wetlands were affected by wetland design, vegetation, water levels, surrounding habitat, fish presence and distance to source wetlands.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F880https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F880Fri, 13 Sep 2013 11:16:59 +0100Collected Evidence: Collected Evidence: Head-start amphibians for release Twenty-two studies head-started amphibians from eggs and monitored them after release. Six of 10 studies (including five replicated studies) in Denmark, Spain, the UK and USA and a global review found that released head-started tadpoles, metamorphs or juveniles established breeding frog populations or increased populations of frogs or toads. Two found mixed results with breeding populations established in 12 of 17 studies reviewed or at two of four sites. Two found that head-started metamorphs or adults did not prevent a frog population decline or establish a breeding toad population. For five of the studies, release of captive-bred individuals, translocation or habitat management were also carried out. Nine of 10 studies (including nine replicated studies) in Australia, Canada, Europe and the USA found that head-started amphibians released as tadpoles, metamorphs or adults metamorphosed successfully, tended to survive the first season, winter or year or bred successfully. One found adult survival was 1–17% over four years and one found limited breeding following the release of adults. Four replicated studies in Australia, the UK and USA found that frog survival to metamorphosis and size at metamorphosis was greater and time to metamorphosis shorter in head-started compared to wild animals. One replicated study in Canada found that young head-started leopard frogs were smaller than those in the wild. One replicated study in Australia found that corroboree frog tadpoles released earlier had higher survival, but metamorphosed two weeks later than those released a month later. Three studies (including one replicated study) in the USA only provided results for head-starting in captivity. Two found that Houston toad eggs could be captive-reared to tadpoles, but only one successfully reared adults. Three studies (including two replicated studies) in Canada and the USA found that during head-starting, amphibian growth rate, size, stress levels and survival was affected by the amount of protein provided, housing density or enclosure location. One found that mass, stress levels and survival were not affected by the amount of food or habitat complexity.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F881https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F881Fri, 13 Sep 2013 13:02:34 +0100Collected Evidence: Collected Evidence: Install culverts or tunnels as road crossings Thirty-two studies investigated the effectiveness of installing culverts or tunnels as road crossings for amphibians. Six of seven studies (including three replicated studies) in Canada, Germany, Italy, Hungary and the USA found that installing culverts or tunnels significantly decreased amphibian road deaths; in one study this was the case only when barrier fencing was also installed. One found no effect on road deaths. Fifteen of 24 studies (including one review and 17 replicated studies) in Australia, Canada, Europe and the USA found that culverts/tunnels were used by amphibians, by 15–85% of amphibians or 3–15 species, or that 23–100% of culverts or tunnels were used by amphibians or used in 12 of 14 studies reviewed. The majority of culverts/tunnels had barrier fencing to guide amphibians to entrances. Four found mixed effects depending on species, or for toads depending on the site or culvert type. Five found that culverts were used by less than 10% of amphibians or were not used. The use of culverts/tunnels was affected by diameter in three of six studies, with wider culverts used more, length in one of two studies, with long culverts avoided, lighting in all three studies, with mixed effects, substrate in three of six studies, with natural substrates used more, presence of water in two of three studies, with mixed effects, entrance location in one and tunnel climate in one study. Six studies (including one replicated, controlled study) in Canada, Spain, the Netherlands and USA investigated the use of culverts with flowing water and found that they were used by amphibians, or rarely used by salamanders or not used, and were used more or the same amount as dry culverts. Certain culvert designs were not suitable for amphibians; one-way tunnels with vertical entry chutes resulted in high mortality of common toads and condensation deposits from steel culverts had very high metal concentrations. One study found that thousands of amphibians were still killed on the road.  Collected Evidencehttps%3A%2F%2Fwww.conservationevidence.com%2Factions%2F884https%3A%2F%2Fwww.conservationevidence.com%2Factions%2F884Mon, 16 Sep 2013 12:20:30 +0100
What Works 2021 cover

What Works in Conservation

What Works in Conservation provides expert assessments of the effectiveness of actions, based on summarised evidence, in synopses. Subjects covered so far include amphibians, birds, mammals, forests, peatland and control of freshwater invasive species. More are in progress.

More about What Works in Conservation

Download free PDF or purchase
The Conservation Evidence Journal

The Conservation Evidence Journal

An online, free to publish in, open-access journal publishing results from research and projects that test the effectiveness of conservation actions.

Read the latest volume: Volume 21

Go to the CE Journal

Discover more on our blog

Our blog contains the latest news and updates from the Conservation Evidence team, the Conservation Evidence Journal, and our global partners in evidence-based conservation.

Who uses Conservation Evidence?

Meet some of the evidence champions

Endangered Landscape ProgrammeRed List Champion - Arc Kent Wildlife Trust The Rufford Foundation Save the Frogs - Ghana Mauritian Wildlife Supporting Conservation Leaders
Sustainability Dashboard National Biodiversity Network Frog Life The international journey of Conservation - Oryx Cool Farm Alliance UNEP AWFA Bat Conservation InternationalPeople trust for endangered species Vincet Wildlife Trust
For a full list of, and information about, our champions:
All Evidence Champions
About our champions, why and how to become one:
Become an Evidence Champion

This website uses Cookies

We use limited Cookies to run the site and to analyse our traffic (none for site vendors). By using this site, you will be providing your consent to our use of Cookies.

Accept & continue