Legally protect reptile species

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages



  • Abundance (2 studies): One of two studies (including one replicated, site comparison study and one before-and-after study) in the USA and Australia found that waterbodies where turtle harvesting was prohibited had a similar abundance of red-eared sliders and Texas spiny softshell turtles compared to unprotected waterbodies. The other study found that following legal protection and harvest regulation, the density of saltwater crocodile populations increased.
  • Reproductive success (1 studies): One before-and-after study in the Seychelles found that following legal protection of both green turtles and their habitat, nesting activity increased.
  • Condition (2 studies): Two studies (including one replicated, site comparison study and one before-and-after study) in the USA and Australia found that in areas with legal protection and/or harvest regulation, Texas spiny softshell turtles and saltwater crocodiles were larger than in areas with no protection or before protection began. One study also found that female red-eared sliders were larger, but males were a similar size in protected compared to unprotected waterbodies.


OTHER (3 studies)

  • Human behaviour change (3 studies): Two reviews in the Netherlands found that despite legislation protecting reptiles and their habitat, only one of four development projects completed their habitat compensation requirements or that compensatory slow worm habitat was not completed in time. Both studies also found that monitoring data was not available or that the success of a slow worm mitigation translocation could not be assessed. One replicated, before-and-after study in Cape Verde reported that following legal protections combined with public awareness campaigns, self-reported harvesting, selling and purchasing of sea turtles and turtle products decreased.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

  1. A review of habitat compensation for protected reptiles in the Netherlands (Bosman et al. 2011) found that legislation was not effective at protecting habitats and reptiles. Only one of four development projects completed habitat compensation measures as set out within legal contracts. Some of the compensation required was provided in two projects (36–68%) and none by one project. Two projects created compensation habitat after destroying habitat, rather than before as required, and the timing was unknown for the remaining two projects. No monitoring data were available from any project. In the Netherlands, reptile species are protected and loss of habitat for these species must be compensated by creating new equivalent habitat. Thirty-one projects required to undertake compensation were selected from government files, of which four had commenced and impacted reptiles. Projects were assessed on the implementation of proposed measures in the approved dispensation contracts and on monitoring data. Field visits were undertaken.

    Study and other actions tested
  2. A replicated, site comparison study in 2008–2009 of freshwater sites in Texas, USA (Brown et al. 2011) found that prohibiting freshwater turtle harvesting in public water bodies did not increase turtle abundance but did increase the size of Texas spiny softshell turtles Apalone spinifera and female red-eared sliders Trachemys scripta compared to unprotected water bodies. One–two years after protections were introduced, red-eared slider and Texas spiny softshell turtle abundance was similar in protected waterbodies (slider: 0.15; softshell: 0.01 turtles/trap day) compared to unprotected waterbodies (slider: 0.12; softshell: 0.05 turtles/trap day). Both male and female Texas spiny softshells were longer in protected waterbodies (male: 171 mm; female: 352 mm) than unprotected waterbodies (male: 151 mm; female: 276 mm). Female red-eared sliders were longer on average in protected waterbodies (222 mm) than unprotected waterbodies (210 mm), whereas males were not (protected: 161 mm; unprotected: 163 mm). From 2007, commercial harvest of freshwater turtles was prohibited in public waterbodies (‘protected’) but unregulated in private waterbodies (‘unprotected’). Turtles were monitored using baited hoop nets in 12 public and 48 private waterbodies spread across three counties (17–22 sites/county > 1 km apart; 5,245 trap days) in May–June 2008 and May–July 2009. Harvest levels were high in two counties and low in one county (see original paper for details). Turtles were marked and carapace lengths were measured.

    Study and other actions tested
  3. A before-and-after study in 1975–2009 in 12 tidal rivers in the Northern Territory, Australia (Fukuda et al. 2011) found that after legal protection and regulated harvests, saltwater crocodile Crocodylus porosus increased in density and average crocodile size recorded increased over time. After saltwater crocodiles were legally protected and harvests regulated, relative density of non-hatchling crocodiles increased by >three times (2009 estimate: 5.3 crocodiles/km; 1975 estimate: 1.5 crocodiles/km). The proportion of larger crocodiles (>1.8 m in length) increased over time in all rivers (most common size in 2007–2008: 2.7 m long, and in 1978–1979: 1.5 m long). Saltwater crocodiles were legally protected in the Northern Territory in 1971. Harvest of non-hatchling crocodiles was limited to <200/year and commercial fishing was banned on most rivers. A managed egg harvest was introduced in 1984–2009 (see original paper for details). Crocodiles were surveyed in 12 large tidal rivers using standardized approach (spotlight surveys at night by boat) in June–October in 1975–2009 (11–29 survey years/river, 33–138 km long surveys/river, 682 km total survey length). Crocodile size was estimated when possible, and only crocodiles >0.6 m (‘non-hatchlings’) were reported. Relative non-hatchling crocodile densities were estimated using the sightings data divided by the length of river surveyed.

    Study and other actions tested
  4. A before-and-after study in 1968–1976 and 1981–2008 on sandy beaches on an atoll island, Aldabra atoll, Seychelles (Mortimer et al. 2011) found that legal protection for green turtles Chelonia mydas, followed by protection of the whole island 15 years later, resulted in an increase in nesting activity. Results were not statistically tested, and the effects of species and habitat protection cannot be separated. Overall nesting activity was estimated to be higher 36–40 years after turtle protection began (2004–2008: 28,200 nesting attempts/year) compared to 13–17 years after turtle protection began (1981–1985: 10,900–16,500 nesting attempts/year). Authors also reported that estimates of nesting activity around the time that turtle protection began ranged from sightings of seven females (11-day survey in 1967), to 2,000–3,000 nests/year (surveys during 1968–1970 and 1975–1976). Protection for turtles began in 1968, with the Green Turtle Protection Regulations 1968, and the atoll became a UNESCO World Heritage Site in 1983. In 1981–2008, up to 68 nesting beaches on the atoll were surveyed for turtle tracks and evidence of nesting. Survey effort was variable between different years and beaches, with beaches surveyed 0–37 times/years in 1981–1994, and 4–171 times/month in 1995–2008.

    Study and other actions tested
  5. A review in 2011 of compliance with legislation during development projects in the Netherlands (Spitzen-van der Sluijs et al. 2011) found that evidence was not provided to suggest that legislation protected a population of slow worms Anguis fragilis. Mitigation translocations of slow worms to a compensatory area began in 2009, but the new habitat was only considered finished in the year following translocations and so slow worms were released into potentially unsuitable habitat. Monitoring before and after translocation was insufficient to determine population numbers or to assess translocation success. In June–September 2009, one hundred and forty-nine slow worms were translocated from a 1.1 ha area of rough grassland to a 2.1 ha compensation area. In the Netherlands, the Flora and Fauna Act protects amphibians. The development project was required by law to provide a compensation area for slow worms and to translocate the species from the development site to that area.

    Study and other actions tested
  6. A replicated, before-and-after study in 2011 on Santiago and Boa Vista islands, Cape Verde (Hancock et al. 2017) reported that after implementing legal frameworks to penalise killing and consumption of marine turtles and protect turtle nests on beaches, as well as public awareness raising campaigns, participation in consumption of turtle products, turtle harvesting and, in some locations, selling turtle products, declined. Results were not statistically tested. After national legal protections for marine turtles were introduced, fishers self-reported a decline in turtle harvesting from 61–87% to 17–18% of survey participants between 2002 and 2011. Fish sellers self-reported a decline in selling turtle products from 78% to 22% of participants on Santiago between 2002 and 2011 (on Boa Vista only one seller self-identified as selling turtle products and continued to do so). The general public self-reported a decline in turtle product consumption on both islands (Boa Vista: 28% decline, Santiago: 62). However, the authors also reported a significant increase in commercial use of turtle meat with trade increasing between Boa Vista and Santiago (see original paper). In 2005 and 2010, legal frameworks were put in place to penalize killing and consumption of marine turtles. Turtle nests on beaches were protected by the military and public awareness campaigns were carried out by local and international NGOs. In May–June 2011, interviews were carried out with individuals from Santiago and Boa Vista coastal communities. Survey participants were fishers (Boa Vista: 46 individuals; Santiago: 82), fish sellers (5; 18) and the general public (94, 189).

    Study and other actions tested
Please cite as:

Sainsbury K.A., Morgan W.H., Watson M., Rotem G., Bouskila A., Smith R.K. & Sutherland W.J. (2021) Reptile Conservation: Global Evidence for the Effects of Interventions for reptiles. Conservation Evidence Series Synopsis. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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Reptile Conservation

This Action forms part of the Action Synopsis:

Reptile Conservation
Reptile Conservation

Reptile Conservation - Published 2021

Reptile synopsis

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