Regulate wildlife harvesting

Supporting evidence from individual studies

1. A replicated study in 1995 and 2004 in a community in Ostional, Costa Rica (Campbell et al. 2007) found that a regulated harvest of olive ridley turtle Lepidochelys olivacea eggs resulted in community members reporting a willingness to do more to protect turtles. A majority of survey respondents reported a willingness to do more to protect sea turtles in 1995 (67%) and in 2004 (78%). A long running programme (over 20 years at time of publication) of legalized turtle egg harvesting was established and run by a community cooperative. The project made use of the “arribada”: a phenomenon of mass nesting by olive ridley turtles on nesting beaches. Members could harvest and sell turtle eggs and also carry out a range of activities relating to turtle protection, including beach cleaning, guarding and ‘liberating’ hatchlings (details of this not provided). A survey of households was carried out in 1995 (76 households) and followed up in 2004 (60 households).

   Study and other actions tested

   Referenced paper

   Campbell L.M., Haalboom B.J. & Trow J. (2007) Sustainability of community-based conservation: Sea turtle egg harvesting in Ostional (Costa Rica) ten years later. Environmental Conservation, 34, 122-131.

2. A before-and-after study in 1975–2009 in 12 tidal rivers in the Northern Territory, Australia (Fukuda et al. 2011) found that after introducing regulated egg harvests and legal protection, saltwater crocodiles Crocodylus porosus increased in population density and average crocodile size increased over time. After saltwater crocodile harvests were regulated, relative population density of crocodiles (excluding hatchling crocodiles <0.6 m in length) increased by >three times (2009 estimate: 5 crocodiles/km; 1975 estimate: 2 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 (harvests in 1983–1986: 994–3,470 eggs, increasing to <50,000 in 2009–2010, see original paper for details). Saltwater crocodiles were surveyed in 12 large tidal rivers using a 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 river length surveyed). Crocodile size was estimated when possible and only crocodiles >0.6 m (‘non-hatchlings’) were reported. Relative non-hatchling crocodile population densities were estimated using the sightings data divided by the length of river surveyed.

   Study and other actions tested

   Referenced paper

   Fukuda Y., Webb G., Manolis C., Delaney R., Letnic M., Lindner G. & Whitehead P. (2011) Recovery of saltwater crocodiles following unregulated hunting in tidal rivers of the Northern Territory, Australia. Journal of Wildlife Management, 75, 1253-1266.

3. A study in 1999 and 2005–2006 in Indonesia (Nijman et al. 2012) reported that regulating reptile harvests through quotas did not limit the number of tokay geckos Gekko gecko, Javan filesnakes Acrochordus javanicus and Asiatic softshell turtles Amyda cartilaginea that were harvested and exported. Trade in tokay geckos was estimated at 1.2 million individuals/year, compared to an annual quota of 50,000; trade in Javan filesnakes was estimated at 330,000 individuals/year, compared to a quota of 200,000; and trade in Asiatic softshell turtles was estimated at 200,000–450,000 in 1998 and 1999 in three cities, compared to a national quota of 10,000. The Indonesian authorities set annual quotas for the harvest and export of reptile species that were not legally protected, and determined quota numbers through consultation with various stakeholders, including reptile traders. Data on trade were collected from the Indonesian authorities (CITES Management Authority), as well as through interviews with members of reptile and amphibian trade associations and other stakeholders in the reptile trade. In 1999, trade data for Asiatic softshell turtles was collected from reptile traders in three cities in Sumatra. In 2005–2006, trade data for tokay geckos was collected at four locations in Java, and Javan filesnake data was collected in five cities and involved all major exporters in the country.

   Study and other actions tested

   Referenced paper

   Nijman V., Shepherd C.R., Mumpuni . & Sanders K.L. (2012) Over-exploitation and illegal trade of reptiles in Indonesia. The Herpetological Journal, 22, 83-89.

4. A before-and-after study in 1975–2015 in two island groups in Ogasawara, Japan (Kondo et al. 2017) found that in the years following regulations to limit the annual harvest of green turtles Chelonia mydas and a long-term programme of allowing harvested females to lay eggs before being killed the estimated number of nesting female turtles and hatchlings tended to be higher. Results were not statistically tested, and the effects of the interventions cannot be separated. The estimated number of nesting female turtles tended to be higher following regulations (180–580 turtles/year) compared to before regulation (25–210 turtles/year) and in years that regulation started (110–205 turtles/year). The number of hatchlings produced in natural nests was also higher in years after regulations were put in place (10,000–95,000 hatchlings/year) than before (0–16,000 hatchling/year). Fisheries regulations implemented in 1994 and 1997 limited the annual catch to 150 and then 135 turtles/year respectively. In 1975–2008, harvested female turtles were taken to an enclosed beach to lay multiple clutches of eggs before being killed. Surveys were conducted in May–September 1975–2015 (Chichi-jima islands) and 1988–2015 (Haha-jim islands) and used the number of nests to estimate abundance of females (see paper for details). In July–November, nests were excavated, and hatchling numbers were estimated by counting empty shells.

   Study and other actions tested

   Referenced paper

   Kondo S., Morimoto Y., Sato T. & Suganuma H. (2017) Factors affecting the long-term population dynamics of green turtles (Chelonia mydas) in Ogasawara, Japan: influence of natural and artificial production of hatchlings and harvest pressure. Chelonian Conservation and Biology, 16, 83-92.