Collected Evidence: Collected Evidence: Release captive-bred reptiles into the wild: Snakes & lizards Ten studies evaluated the effects on reptile populations of releasing captive-bred snakes and lizards into the wild. Three studies were in New Zealand, two were in the USA and one was in each of the Galápagos, Spain, Australia and Canada and one was global. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (10 STUDIES) Abundance (2 studies): One global review found that when using recruitment to the adult population as a measure of success, 32% of reptile releases (releases of captive individuals were 7% of total projects) were successful. One review in New Zealand found that 13% of lizard releases (some involving captive-bred animals) found evidence of populations growth Reproductive success (3 studies): Three studies (including two reviews) in the USA and New Zealand found evidence of breeding following release in one of two captive-bred populations of cornsnakes, one captive-bred population of Otago skinks and in at least 16 lizard mitigation translocations, some of which involved captive-bred animals. Survival (9 studies): One replicated, controlled study in Spain found that released large psammodromus lizards had similar annual survival compared to resident lizards. Two of six studies (including one replicated study and two reviews) in the USA, Australia, New Zealand and Canada reported that 13% of 40 indigo snakes were re-sighted at least once during 5–8 years following release or that 58% of 12 Otago skinks survived at least 18 months. Two studies found that zero of nine and 27 individuals survived more than 143 days or beyond their first hibernation. The other two studies found that one of two and five of 53 releases (only some of which involved captive-bred animals) failed completely (no individuals survived). One study in New Zealand found that survival of captive-bred Otago skinks released into an enclosure was higher when mice had been eradicated compared to when skinks were released in the presence of mice. One replicated study in the Galápagos found that while releases were ongoing over a decade (183 released in total), 17–32 Galápagos land iguanas were recaptured each year. Condition (1 study): One controlled study in New Zealand found that body condition of captive-reared Otago skinks was higher than wild skinks, but sprint speed was lower. BEHAVIOUR (1 STUDY) Behaviour change (1 study): One replicated, controlled study in Spain found that released large psammodromus lizards moved between habitat fragments more frequently than resident lizards but showed similar behaviour in three other measures. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3771https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3771Wed, 15 Dec 2021 11:29:15 +0000Collected Evidence: Collected Evidence: Release captive-bred reptiles into the wild: Crocodilians Four studies evaluated the effects of releasing captive-bred crocodilians into the wild. Two studies were in China, one was in South Africa and one was a global review. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (4 STUDIES) Abundance (2 studies): One global review found that when using recruitment to the adult population as a measure of success, 32% of reptile translocations/releases (releases of captive individuals were 7% of total projects) were successful. One study in South Africa reported that following releases of captive-bred Nile crocodiles, wild populations increased in size over 30 years, but then declined in the subsequent 15 years. Reproduction (2 studies): Two studies (one replicated) in China reported that breeding or nesting was observed within four years of releasing captive-bred Chinese alligators. Survival (1 study): One study in China reported that of nine captive-bred Chinese alligators, three survived for nine years and six survived for at least one year following release. BEHAVIOUR (1 STUDY) Use (1 study): One replicated study in China reported that after 10 years of releases of captive bred Chinese alligators to an area that had historically been occupied, 56% of constructed ponds were occupied. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3772https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3772Wed, 15 Dec 2021 11:53:57 +0000Collected Evidence: Collected Evidence: Release captive-bred reptiles into the wild: Tuatara Two studies evaluated the effects of releasing captive-bred tuatara into the wild. One study was in New Zealand and one was a global review. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (1 STUDY) Abundance (1 study): One global review found that when using recruitment to the adult population as a measure of success, 32% of reptile translocations/releases (releases of captive individuals were 7% of total projects) were successful. Condition (1 study): One study in New Zealand found that tuatara reared close to the release site had higher growth, but similar body condition compared to individuals reared in a warmer climate. BEHAVIOUR (1 STUDY) Behaviour change (1 studies): One study in New Zealand found that tuatara reared close to the release site had similar home range sizes and post-release dispersal compared to individuals reared in a warmer climate. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3773https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3773Wed, 15 Dec 2021 12:02:09 +0000Collected Evidence: Collected Evidence: Use holding pens or enclosures at release site prior to release of captive-bred reptiles Two studies evaluated the effects on reptile populations of using holding pens or enclosures at release sites prior to release of captive-bred reptiles. Both studies were in the USA. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (2 studies): Two controlled studies (including one replicated study) in the USA found that survival of captive-bred smooth green snakes and desert tortoises held in pens before release was similar over 3–5 months or 2–3 years compared to individuals released directly. BEHAVIOUR (1 STUDY) Behaviour change (1 study): One controlled study in the USA found that movement of smooth green snakes held in pens before release was similar compared to snakes that were released directly. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3774https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3774Wed, 15 Dec 2021 12:04:46 +0000Collected Evidence: Collected Evidence: Head-start wild-caught reptiles for release: Sea turtles Seven studies evaluated the effects of head-starting wild-caught sea turtles for release. Two studies were in the Caribbean Sea and one was in each of the Torres Strait, northern Australia, the Gulf of Mexico, Japan, the USA and Thailand. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (6 STUDIES) Abundance (1 studies): One replicated, before-and-after study in the USA found that over the course of a 37-year head-start programme, the number of kemp’s ridley nests laid on the Texas coastline increased from near zero to 119. Reproductive success (2 studies): Two studies (including one replicated, before-and-after study) in Mexico and the USA found that all 11 head-started Kemp’s ridley turtles bred in the wild following release and head-started turtles that were allowed to crawl to the sea before recapture began laying nests on their beach of origin 10–12 years after release. Survival (4 studies): One of four studies (including two replicated and two controlled studies) in the Caribbean Sea, Torres Strait near Australia, Gulf of Mexico and Japan reported that all 11 head-started Kemp’s ridley turtles survived at least 11–19 years following release. Two of the studies reported that 1–16% of sea turtles were recaptured 10–27 month or 0.5–13 months following release. The other study found that four head-started hawksbill turtles survived at least 4–9 days, and one survived at least 10 months following release. Condition (1 study): One replicated study in Thailand found mixed effects of tank depth on growth rate, size and body condition of green turtles during a head-starting programme and no effect of feed type. BEHAVIOUR (2 STUDIES) Use (1 study): One replicated study in the Caribbean Sea reported that one head-started green turtle travelled 2,300 km from its release location, whereas other recaptures were within 1–14 km of the release site. Behaviour change (1 study): One replicated study in the Caribbean Sea found mixed effects on swimming behaviour of released head-started loggerhead turtles at 1.5 years old compared to 2.5 years old. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3775https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3775Wed, 15 Dec 2021 12:21:11 +0000Collected Evidence: Collected Evidence: Head-start wild-caught reptiles for release: Tortoises, terrapins, side-necked & softshell turtles Eighteen studies evaluated the effects of head-starting wild-caught tortoises, terrapins, side-necked and softshell turtles for release. Thirteen studies were in the USA, two were in Venezuela and one was in each of the Galápagos, Poland and Madagascar. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (18 STUDIES) Abundance (1 study): One controlled study in Venezuela found that 57% of captured giant sideneck river turtles were head-started individuals. Survival (13 studies): Two of three studies (including one replicated, controlled study) in the USA and Poland found that head-started European pond turtles and desert tortoises had similar survival compared to wild turtles or hatchlings released directly into the wild. The other study found that head-started northern redbelly turtles had higher survival than wild hatchling turtles. This study also found that in the first year of release, larger head-started turtles had higher survival, but in year 2–3 survival was similar for all sizes. Four of 12 studies (including nine replicated studies) in the Galápago, the USA, Madagascar and Venezuela reported that 50–100% of head-started individuals survived for three months to 1–5 years after release. Three of the studies reported that 6–43% of individuals survived for 1–3 years. Two of the studies reported that six of six, two of 10 and nine of 10 radio-tracked individuals survived 3–12 months. Two of the studies reported that annual survival was 80–100% or 3–100% in the year following release but 82–100% in subsequent years. The other study reported that some giant sideneck river turtles survived up to 14 years. Two studies also reported that survival during the captive phase was 91–100%. One study also found that more tortoises head-started in outdoor seaside pens died than did those from indoor pens. One replicated, controlled study in Venezuela found that survival of Arrau turtles during the captive phase was lower for turtles from relocated nests compared to those from nests that were not moved. Condition (5 studies): One of two replicated studies in the USA found that two-year-old head-started gopher tortoises were larger at their time of release than two-year-old tortoises released in to the wild directly after hatching. The other study found that Agassiz’s desert tortoise hatchlings grew more slowly in captivity than tortoises in the wild. Two studies (including one replicated study) in the USA found that Alabama red-bellied cooters and wood turtles grew during 12–16 months in captivity, and wood turtles showed no signs of shell malformation. One controlled study in Venezuela found that the size distribution of released head-started giant sideneck river turtles was similar to that of wild turtles when newly released individuals were excluded. BEHAVIOUR (1 STUDY) Use (1 study): One study in the USA found that 81% of desert tortoises established home ranges within 13 days of release. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3776https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3776Wed, 15 Dec 2021 12:31:41 +0000Collected Evidence: Collected Evidence: Head-start wild-caught reptiles for release: Snakes & lizards Nine studies evaluated the effects of head-starting wild-caught snakes and lizards for release. Five studies were in the USA, two were in Puerto Rico and one was in each of the Cayman Islands and Jamaica. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (9 STUDIES) Abundance (2 studies): Two studies (including one before-and-after and one replicated study) in Jamaica and the Cayman Islands reported that the number of Jamaican iguanas found in the wild was higher after 23 years of head-starting and releasing compared to at the start of the programme and that there was a stable population of blue iguanas over four years during ongoing releases of head-started individuals. Reproductive success (4 studies): Four studies (including two replicated studies) in Jamaica, Puerto Rico and the USA reported successful reproduction following release of head-started Jamaican iguanas (but not for 16 years) and Mona Island iguanas, and that timber rattlesnakes copulated or participated in pre-copulatory behaviour. One study also reported that 88–90% of Mona Island iguana eggs hatched successfully. Survival (8 studies): Two of three controlled studies (including one replicated, randomized study) in the USA found that head-started plains gartersnakes and common water snakes were recaptured a similar number of times or had similar survival compared to resident snakes. The other study found that head-started northern water snakes had lower survival following release than resident snakes. One study also found that 76% of snakes survived the captive phase of head-starting. Three studies (including two replicated studies) in the USA and Puerto Rico reported that 22–40% of timber rattlesnakes or Mona Island iguanas survived for monitoring periods of eight months to six years. One replicated study in the USA found that head-started eastern massasaugas released in summer had higher survival than snakes released in autumn. One before-and-after study in Jamaica reported that 16% of Jamaican iguanas died during the captive phase of head-starting. Condition (5 studies): Two of three controlled studies (including one replicated, randomized study) in the USA found that head-started northern water snakes and common water snakes grew more slowly than resident snakes. The other study found that head-started plains gartersnakes had similar growth rates to resident snakes. One study also found that head-started common water snakes had similar body condition to resident snakes. One controlled study in Puerto Rico found that body condition of head-started Mona Island iguanas was higher than wild iguanas before release, but similar at their first recapture after release. One replicated study in the USA found that more head-started eastern massasaugas released in summer gained weight before hibernation than snakes released in autumn. BEHAVIOUR (3 STUDIES) Behaviour change (3 studies): One of three studies (including one replicated, randomized, controlled study) in the USA found that head-started common water snakes showed similar behaviour to residents across a range of behaviour measures. One of the studies found that head-started northern water snakes had smaller home ranges and showed less surface activity than resident snakes. The other study found that head-started eastern massasaugas released in summer had larger home ranges than snakes released in autumn. Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3777https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3777Wed, 15 Dec 2021 13:03:25 +0000Collected Evidence: Collected Evidence: Head-start wild-caught reptiles for release: Crocodilians Seven studies evaluated the effects of head-starting wild-caught crocodilians for release. Two studies were in each of the Philippines and Nepal and one study was in each of Zimbabwe, Venezuela and Argentina. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (7 STUDIES) Abundance (2 studies): Two studies (including one replicated study) in the Philippines and Nepal reported that following releases of head-started crocodiles or gharials, wild populations increased in size over 8–9 years. Reproductive success (2 studies): One replicated study in Argentina reported that released head-started broad-snouted caimans had similar clutch sizes and hatching success compared to non-head-started caiman. One replicated study in Nepal reported successful reproduction in all four rivers where head-started gharials were released. Survival (5 studies): Three studies (including one replicated, controlled study) in Venezuela, the Philippines and Nepal reported that 88% of head-started Orinoco crocodiles survived 8–12 months and 53% of Philippine crocodiles or gharials survived for one year following release. One study also found that survival of Philippine crocodile hatchlings during the captive phase of head-starting was higher than for non-head-started hatchlings in the wild. One replicated study in Argentina reported that at least five released head-started broad-snouted caimans survived 9–10 years. One replicated study in Zimbabwe found that 38% of released head-started Nile crocodiles were recaptured at least once over four years. This study also found that hatching success of Nile crocodile eggs in the head-start programme was 74%, and that survival of hatchlings during the captive phase was lowest during the first year. Condition (1 studies): One study in Venezuela found that released head-started Orinoco crocodiles grew at a similar rate to resident juvenile crocodiles. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3778https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3778Wed, 15 Dec 2021 13:26:54 +0000Collected Evidence: Collected Evidence: Head-start wild-caught reptiles for release: Tuatara Two studies evaluated the effects of head-starting wild-caught tuatara for release. Both studies were in New Zealand. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (2 STUDIES) Survival (2 studies): One study in New Zealand reported that 67–70% of head-started tuatara survived over monitoring periods of 9–11 months. One study in New Zealand found that 56% of head-started tuatara were recaptured over six years following release. Condition (1 studies): One study in New Zealand reported that head-started tuatara increased in weight by around 100 g during the five years following release. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3779https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3779Wed, 15 Dec 2021 13:42:27 +0000Collected Evidence: Collected Evidence: Release reptiles born/hatched in captivity from wild-collected eggs/wild-caught females without rearing Five studies evaluated the effect on reptile populations of releasing reptiles born/hatched in captivity from wild-collected eggs/wild-caught females without rearing. Four studies were in the USA and one was in Australia. COMMUNITY RESPONSE (0 STUDIES) POPULATION RESPONSE (5 STUDIES) Reproductive success (1 study): One replicated, controlled study in the USA found that for plains gartersnakes released as newborns, two of over 350 released snakes were found to be gravid two years after release. Survival (5 studies): One before-and-after study in the USA found that survival of captive-born desert tortoises released as hatchlings was similar over six months compared to hatchlings that were head-started in indoor or outdoor enclosures. One replicated, controlled study in the USA found that alligator hatchlings released into their mother’s home range had higher survival than those released outside her home range. Three replicated studies (including one controlled study) in Australia and the USA found that 11% of Murray short-necked turtles and 7% of plains gartersnakes survived for 1–3 years after release, and first year survival of gopher tortoise hatchlings released into a predator proof enclosure was around 30%. Condition (2 studies): One before-and-after study in the USA found that captive-born desert tortoises released as hatchlings grew more slowly over six months than hatchlings head-started in an indoor enclosure. One replicated, controlled study in the USA found mixed effects on growth of alligator hatchlings released inside or outside of their mother’s home range compared to wild hatchlings. BEHAVIOUR (0 STUDIES)Collected Evidencehttps%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3780https%3A%2F%2Fconservationevidencejournal.com%2Factions%2F3780Wed, 15 Dec 2021 14:31:38 +0000
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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.

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