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What Works in Conservation 2017

 | 
William J. Sutherland
, 
Lynn V. Dicks
, 
Nancy Ockendon
, 
et al.

1. AMPHIBIAN CONSERVATION

1.8 Threat: Invasive and other problematic species

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1.8.1 Reduce predation by other species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing predation by other species?

Beneficial

● Remove or control fish by drying out ponds

Likely to be beneficial

● Remove or control fish population by catching
● Remove or control invasive bullfrogs
● Remove or control invasive viperine snake
● Remove or control mammals

Trade-off between benefit and harms

● Remove or control fish using Rotenone

Unknown effectiveness (limited evidence)

● Exclude fish with barriers

No evidence found (no assessment)

● Encourage aquatic plant growth as refuge against fish predation
● Remove or control non-native crayfish

Beneficial

Remove or control fish by drying out ponds

1One before-and-after study in the USA found that draining ponds to eliminate fish increased numbers of amphibian species. Four studies, including one review, in Estonia, the UK and USA found that pond drying to eliminate fish, along with other management activities, increased amphibian abundance, numbers of species and breeding success. Assessment: beneficial (effectiveness 80%; certainty 66%; harms 3%).
http://www.conservationevidence.com/​actions/​826

Likely to be beneficial

Remove or control fish population by catching

2Four of six studies, including two replicated, controlled studies, in Sweden, the USA and UK found that removing fish by catching them increased amphibian abundance, survival and recruitment. Two found no significant effect on newt populations or toad breeding success. Assessment: likely to be beneficial (effectiveness 50%; certainty 52%; harms 0%).
http://www.conservationevidence.com/​actions/​827

Remove or control invasive bullfrogs

3Two studies, including one replicated, before-and-after study, in the USA and Mexico found that removing American bullfrogs increased the size and range of frog populations. One replicated, before-and-after study in the USA found that following bullfrog removal, frogs were found out in the open more. Assessment: likely to be beneficial (effectiveness 79%; certainty 60%; harms 0%).
http://www.conservationevidence.com/​actions/​825

Remove or control invasive viperine snake

4One before-and-after study in Mallorca found that numbers of Mallorcan midwife toad larvae increased after intensive, but not less intensive, removal of viperine snakes. Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).
http://www.conservationevidence.com/​actions/​830

Remove or control mammals

5One controlled study in New Zealand found that controlling rats had no significant effect on numbers of Hochstetter’s frog. Two studies, one of which was controlled, in New Zealand found that predator-proof enclosures enabled or increased survival of frog species. Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 0%).
http://www.conservationevidence.com/​actions/​839

Trade-off between benefit and harms

Remove or control fish using Rotenone

6Three studies, including one replicated study, in Sweden, the UK and USA found that eliminating fish using rotenone increased numbers of amphibians, amphibian species and recruitment. One review in Australia, the UK and USA found that fish control that included using rotenone increased breeding success. Two replicated studies in Pakistan and the UK found that rotenone use resulted in frog deaths and negative effects on newts. Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 60%; harms 52%).
http://www.conservationevidence.com/​actions/​828

Unknown effectiveness (limited evidence)

Exclude fish with barriers

7One controlled study in Mexico found that excluding fish using a barrier increased weight gain of axolotls. Assessment: unknown effectiveness — limited evidence (effectiveness 30%; certainty 20%; harms 0%).
http://www.conservationevidence.com/​actions/​829

No evidence found (no assessment)

8We have captured no evidence for the following interventions:

  • Encourage aquatic plant growth as refuge against fish predation

  • Remove or control non-native crayfish

1.8.2 Reduce competition with other species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing competition with other species?

Unknown effectiveness (limited evidence)

● Reduce competition from native amphibians
● Remove or control invasive Cuban tree frogs

No evidence found (no assessment)

● Remove or control invasive cane toads

Unknown effectiveness (limited evidence)

Reduce competition from native amphibians

9One replicated, site comparison study in the UK found that common toad control did not increase natterjack toad populations. Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 23%; harms 0%).
http://www.conservationevidence.com/​actions/​821

Remove or control invasive Cuban tree frogs

10One before-and-after study in the USA found that removal of invasive Cuban tree frogs increased numbers of native frogs. Assessment: unknown effectiveness — limited evidence (effectiveness 65%; certainty 30%; harms 0%).
http://www.conservationevidence.com/​actions/​822

No evidence found (no assessment)

11We have captured no evidence for the following interventions:

  • Remove or control invasive cane toads

1.8.3 Reduce adverse habitat alteration by other species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing adverse habitat alteration by other species?

Likely to be beneficial

● Control invasive plants

No evidence found (no assessment)

● Prevent heavy usage/exclude wildfowl from aquatic habitat

Likely to be beneficial

Control invasive plants

12One before-and-after study in the UK found that habitat and species management that included controlling swamp stonecrop, increased a population of natterjack toads. One replicated, controlled study in the USA found that more Oregon spotted frogs laid eggs in areas where invasive reed canarygrass was mown. Assessment: likely to be beneficial (effectiveness 60%; certainty 47%; harms 0%).
http://www.conservationevidence.com/​actions/​823

No evidence found (no assessment)

13We have captured no evidence for the following intervention:

  • Prevent heavy usage/exclude wildfowl from aquatic habitat

1.8.4 Reduce parasitism and disease–chytridiomycosis

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing chytridiomycosis?

Likely to be beneficial

● Use temperature treatment to reduce infection

Trade-off between benefit and harms

● Use antifungal treatment to reduce infection

Unknown effectiveness (limited evidence)

● Add salt to ponds
● Immunize amphibians against infection
● Remove the chytrid fungus from ponds
● Sterilize equipment when moving between amphibian sites
● Treating amphibians in the wild or pre-release
● Use gloves to handle amphibians

Unlikely to be beneficial

● Use antibacterial treatment to reduce infection
● Use antifungal skin bacteria or peptides to reduce infection

No evidence found (no assessment)

● Use zooplankton to remove zoospores

Likely to be beneficial

Use temperature treatment to reduce infection

14Four of five studies, including four replicated, controlled studies, in Australia, Switzerland and the USA found that increasing enclosure or water temperature to 30–37 ° C for over 16 hours cured amphibians of chytridiomycosis. One found that treatment did not cure frogs. Assessment: likely to be beneficial (effectiveness 60%; certainty 70%; harms 10%).
http://www.conservationevidence.com/​actions/​770

Trade-off between benefit and harms

Use antifungal treatment to reduce infection

15Twelve of 16 studies, including four randomized, replicated, controlled studies, in Europe, Australia, Tasmania, Japan and the USA found that antifungal treatment cured or increased survival of amphibians with chytridiomycosis. Four studies found that treatments did not cure chytridiomycosis, but did reduce infection levels or had mixed results. Six of the eight studies testing treatment with itraconazole found that it was effective at curing chytridiomycosis. One found that it reduced infection levels and one found mixed effects. Six studies found that specific fungicides caused death or other negative side effects in amphibians. Assessment: tradeoffs between benefits and harms (effectiveness 71%; certainty 70%; harms 50%).
http://www.conservationevidence.com/​actions/​882

Unknown effectiveness (limited evidence)

Add salt to ponds

16One study in Australia found that following addition of salt to a pond containing the chytrid fungus, a population of green and golden bell frogs remained free of chytridiomycosis for over six months. Assessment: unknown effectiveness — limited evidence (effectiveness 41%; certainty 25%; harms 50%).
http://www.conservationevidence.com/​actions/​762

Immunize amphibians against infection

17One randomized, replicated, controlled study in the USA found that vaccinating mountain yellow-legged frogs with formalin-killed chytrid fungus did not significantly reduce chytridiomycosis infection rate or mortality. Assessment: unknown effectiveness — limited evidence (effectiveness 0%; certainty 25%; harms 0%).
http://www.conservationevidence.com/​actions/​765

Remove the chytrid fungus from ponds

18One before-and-after study in Mallorca found that drying out a pond and treating resident midwife toads with fungicide reduced levels of infection but did not eradicate chytridiomycosis. Assessment: unknown effectiveness — limited evidence (effectiveness 25%; certainty 25%; harms 0%).
http://www.conservationevidence.com/​actions/​766

Sterilize equipment when moving between amphibian sites

19We found no evidence for the effects of sterilizing equipment when moving between amphibian sites on the spread of disease between amphibian populations or individuals. Two randomized, replicated, controlled study in Switzerland and Sweden found that Virkon S disinfectant did not affect survival, mass or behaviour of eggs, tadpoles or hatchlings. However, one of the studies found that bleach significantly reduced tadpole survival. Assessment: unknown effectiveness — limited evidence (effectiveness 10%; certainty 30%; harms 40%).
http://www.conservationevidence.com/​actions/​768

Treating amphibians in the wild or pre-release

20One before-and-after study in Mallorca found that treating wild toads with fungicide and drying out the pond reduced infection levels but did not eradicate chytridiomycosis. Assessment: unknown effectiveness — limited evidence (effectiveness 27%; certainty 30%; harms 0%).
http://www.conservationevidence.com/​actions/​767

Use gloves to handle amphibians

21We found no evidence for the effects of using gloves on the spread of disease between amphibian populations or individuals. A review for Canada and the USA found that there were no adverse effects of handling 22 amphibian species using disposable gloves. However, three replicated studies in Australia and Austria found that deaths of tadpoles were caused by latex, vinyl and nitrile gloves for 60–100% of species tested. Assessment: unknown effectiveness — limited evidence (effectiveness 9%; certainty 35%; harms 65%).
http://www.conservationevidence.com/​actions/​769

Unlikely to be beneficial

Use antibacterial treatment to reduce infection

22Two studies, including one randomized, replicated, controlled study, in New Zealand and Australia found that treatment with chloramphenicol antibiotic, with other interventions in some cases, cured frogs of chytridiomycosis. One replicated, controlled study found that treatment with trimethoprim-sulfadiazine increased survival time but did not cure infected frogs. Assessment: unlikely to be beneficial (effectiveness 38%; certainty 45%; harms 10%).
http://www.conservationevidence.com/​actions/​763

Use antifungal skin bacteria or peptides to reduce infection

23Three of four randomized, replicated, controlled studies in the USA found that introducing antifungal bacteria to the skin of chytrid infected amphibians did not reduce infection rate or deaths. One found that it prevented infection and death. One randomized, replicated, controlled study in the USA found that adding antifungal skin bacteria to soil significantly reduced chytridiomycosis infection rate in salamanders. One randomized, replicated, controlled study in Switzerland found that treatment with antimicrobial skin peptides before or after infection with chytridiomycosis did not increase toad survival. Assessment: unlikely to be beneficial (effectiveness 29%; certainty 50%; harms 10%).
http://www.conservationevidence.com/​actions/​764

No evidence found (no assessment)

24We have captured no evidence for the following intervention:

  • Use zooplankton to remove zoospores

1.8.5 Reduce parasitism and disease–ranaviruses

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for reducing ranaviruses?

No evidence found (no assessment)

● Sterilize equipment to prevent ranaviruses

No evidence found (no assessment)

25We have captured no evidence for the following intervention:

  • Sterilize equipment to prevent ranaviruses

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