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Podocnemis lewyana 

Scope: Global
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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Reptilia Testudines Podocnemididae

Scientific Name: Podocnemis lewyana
Species Authority: Duméril, 1852
Common Name(s):
English Magdalena River Turtle
French Podocnémide de Léwy
Spanish Tortuga del Río Magdalena
Taxonomic Notes: Genetic studies by Vargas-Ramirez et al. (2006, 2007a, 2012) and Restrepo (2008) have shown that P. lewyana has low levels of genetic variability and no evidence of genetic population structure on a micro or macro-geographic scale, in addition to some level of inbreeding on a local scale.

Assessment Information [top]

Red List Category & Criteria: Critically Endangered A2acd+4acd ver 3.1
Year Published: 2016
Date Assessed: 2015-07-01
Assessor(s): Páez, V., Gallego-Garcia, N. & Restrepo, A.
Reviewer(s): Rhodin, A.G.J., van Dijk, P.P. & Horne, B.D.
Facilitator/Compiler(s): Rhodin, A.G.J.
Justification:

This species has for a long time been classified internationally (IUCN 1996) and in Colombia (Castaño-Mora 2002) as Endangered. Recent studies on the extent of range reductions and demographic declines (Gallego-García and Castaño-Mora 2008; Restrepo et al. 2008; Páez et al. 2009, 2015a; Morales-Betancourt et al. 2015) argue that its classification should be elevated to Critically Endangered, with at least c. 80% population reductions over three generations (c. 30-45 years).  Quantitative analysis (Páez et al. 2015a) in the Magdalena River indicated that generation time is approximately 10 years, and for this population the rate of annual decline is 8.8%. Stochastic projections predicted a local extinction in less than three generations (25 years). Many extant populations throughout the distributional range of the species currently face heavy subsistence and commercial exploitation and several show apparent low densities (Vargas-Ramirez et al. 2006; Páez et al. 2015a). Some populations in the upper San Jorge River have already been extirpated (Vargas-Ramirez et al. 2006; Cárdenas-Arévalo et al. 2015). This species is therfore assessed here as Critically Endangered.

Previously published Red List assessments:

Geographic Range [top]

Range Description:Podocnemis lewyana is endemic to Colombia with its presence documented in the Sinú and Magdalena drainages, including the lower Cauca, San Jorge, and Nechí tributaries (Iverson 1992; Rueda-Almonacid et al. 2007; Páez et al. 2009; Ortiz-Yusti et al. 2014). This distribution makes it a biogeographic anomaly, being the only South American podocnemid turtle to occur northwest of the Andes Mountains instead of inhabiting the Orinoco, Essequibo, or Amazon drainages. Also, there are records of its occurrence in the Ranchería and Cocorná rivers (Hurtado 1973; Rhodin et al. 1978; Restrepo et al. 2008; Ortiz-Yusti et al. 2014; Ceballos et al. 2014). Its distributional limits are the Caribbean Sea to the north, Tolima Department to the south, and Antioquia Department to the west. An isolated population of P. lewyana also occurs above the Rodrigo Echandía Hydroelectric Dam located on the Prado River in Tolima Department in the upper Magdalena drainage. It has also apparently been introduced by Colombian settlers into the Tarra River in the Lake Maracaibo basin of Venezuela (Pauler and Trebbau 1995).
Countries occurrence:
Native:
Colombia
Additional data:
Upper elevation limit (metres):800
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:

Many extant populations throughout the distributional range of the species currently face heavy subsistence and commercial exploitation and several show apparent low densities (Vargas-Ramirez et al. 2006; Páez et al. 2009, 2015a). The only study that has estimated annual survival rates showed that they increase with body size (Páez et al. 2015a).  Some populations in the upper San Jorge River have already been extirpated (Vargas-Ramirez et al. 2006). A quantitative analysis (Páez et al. 2015a) in the Magdalena River involving four years of mark-recapture effort in four sites estimated generation time as approximately 10 years, based on female body size growth data and mean size of nesting females. A projection matrix was constructed from the data from the four sites and a Monte Carlo uncertainty analysis indicated the population was declining at an annual rate of 8.8%. An elasticity analysis indicated that the most important parameter for helping the population recover was survival of adults, followed by survival of other age classes, with survival of eggs and hatchlings having the least effect. Stochastic projections predicted a local extinction there in less than three generations (in approximately 25 years).

Current Population Trend:Decreasing
Additional data:
Continuing decline of mature individuals:Yes
Population severely fragmented:No

Habitat and Ecology [top]

Habitat and Ecology:

Páez et al. (2009, 2012) provided an extensive review of the habitats and ecology of P. lewyana. The species is primarily seen along the banks of rivers, although it is also possible to find individuals in small tributaries, lagoons, and flooded areas connected to rivers. Individuals are often observed basking on banks or fallen trunks along the shoreline, either alone or in groups including various size classes (Gallego-Garcia and Castaño-Mora 2008; Restrepo et al. 2008). Smaller individuals tend to occur in shallower, more turbid waters or in flooded pastures, with adults more selective of deeper, wider channels (Gallego-García and Castaño-Mora 2008; Páez et al. 2015a).

Nesting occurs in sand or gravel beaches, as well as in banks and pastures during the months of low river levels. Mean clutch sizes is 22 eggs, with a range of 10-31 eggs (Dahl and Medem 1964; Medem 1965; Castaño-Mora 1986; Correa-Hernández 2006; Cano 2007; Gallego-García and Castaño-Mora 2008).  Based upon a sample size of approximately 1000 individuals (Páez, unpubl. data) adult males on average measure 24.6 cm SCL (range 20-35 cm) with an average weight of 1.6 kg (range 0.7-4.3 kg), while adult females average 37 cm SCL (range 30-46 cm) and on average weigh 5.6 kg (range 2,2-10.4 kg). Hatchlings measure 42-46 mm SCL and weigh 16-22 gram. It has been documented that P. lewyana nests are laid in both the verano and veranillo low water periods each year, but it is not clear whether individual females nest in both periods each year. However, within each period, there is wide variance around the female size/clutch size regression. This often results in species where females of a given body size lay progressively smaller clutches when re-nesting during a nesting season. It is suspected that female P. lewyana in the study population deposited one or more nests during both nesting seasons each year. Males attain sexual maturity at approximately 20 cm SCL, corresponding to 3-4 years of age. Females first nest at 30 cm SCL, at an approximate age of 5-6 years old. The generation time is approximately 10 years (Páez et al. 2012, Ceballos et al. 2014, González-Zarate et al. 2014, Ortiz-Yusti et al. 2014, Sánchez-Ospina et al. 2014, Zapata et al. 2014, Restrepo et al. 2015, Gallego-García and Páez 2016, Páez et al. 2015a,b).  According to Gallego-Garcia and Forero-Medina (in prep.), P. lewyana has high site fidelity, with males and females exhibiting comparable home range sizes (10.3 ha and 14.6 ha, respectively). In the middle Magdalena drainage, the main nesting season is during the primary dry season, from December to April, with a peak in March, and limited nesting also occurring in the secondary dry season from July to August. In the Prado River of the upper Magdalena drainage, the main nesting period is from June to September and a secondary nesting period occurs from December to May (Vargas-Ramirez, unpubl. data). In the Sinú River, two seasons also have been documented in December to March and June to August (Gallego-García and Castaño-Mora 2008).

Systems:Terrestrial; Freshwater
Continuing decline in area, extent and/or quality of habitat:Yes
Generation Length (years):10-15
Movement patterns:Not a Migrant

Use and Trade [top]

Use and Trade: Podocnemis lewyana is used as a source of protein for local people throughout its range. Various capture techniques are used, including hunting adult females with dogs on land during the nesting season, or in water by setting nets and hooks baited with plantain, or diving for individuals along the bottom of canals. In several fishing villages, turtles are also considered important for traditional medicinal purposes. In these communities, it is believed that consumption of turtles helps women to recover after pregnancy, cures skin and eye diseases, confers longevity and strength, and serves as an aphrodisiac. The nesting season includes Easter week each year, when hunting pressures rise notably to satisfy the demand for “white meat” in the large cities on the nearby Caribbean coast. In the lower Magdalena and Sinú rivers, some people exclusively dedicate their time to the capture, transport, and sale of turtles and eggs.

Threats [top]

Major Threat(s):

Páez et al. (2009, 2012) provided and extensive review of the threats to P. lewyana. Several factors that affect populations of the species have been identified throughout its distributional range: 1) habitat destruction and pollution; 2) traditional utilization and consumption; 3) commercial exploitation; and 4) hydrological changes due to dams (Gallego-Garcia 2004; Vargas-Ramirez et al. 2006, 2007b). Pastures and plantations have replaced original forest throughout a large portion of its territory. At urban centres and localities where extensive agriculture is the principal human activity (e.g., the upper Magdalena River), pollution of beaches and water bodies is common. Podocnemis lewyana is used as a source of protein for local people throughout its range. Various capture techniques are used, including hunting adult females with dogs on land during the nesting season, or in water by setting nets and hooks baited with plantain, or diving for individuals along the bottom of canals. In several fishing villages, turtles are also considered important for traditional medicinal purposes. In these communities, it is believed that consumption of turtles helps women to recover after pregnancy, cures skin and eye diseases, confers longevity and strength, and serves as an aphrodisiac. The nesting season includes Easter week each year, when hunting pressures rise notably to satisfy the demand for “white meat” in the large cities on the nearby Caribbean coast. In the lower Magdalena and Sinú rivers, some people exclusively dedicate their time to the capture, transport, and sale of turtles and eggs.

In the Sinú and tributaries of the Magdalena rivers (such as the Prado, La Miel, and Sogamoso rivers), hydroelectric dams have been constructed. Whenever water is released to produce energy during the dry season, beaches that were exposed become submerged. Flooding may last for several days and several of these flooding episodes may occur during a single dry season. The impact of these events has never been fully evaluated but it is likely that thousands of eggs are inundated and drowned every year (Gallego-García and Castaño-Mora 2008).

When neonates begin to emerge from the nests, they also are hunted with the objective of selling them in the illegal pet trade (Castaño-Mora 1986, 1997; Rueda-Almonacid 1999). Moreover, habitat degradation caused by draining wetlands for agricultural or ranching ventures and the sedimentation of other water bodies seriously jeopardizes the survival chances of the species (Castaño-Mora 1997, 2002; Rueda-Almonacid 1999).

Conservation Actions [top]

Conservation Actions: Podocnemis lewyana was last assessed by the IUCN TFTSG in 1996 as Endangered (EN) A1bd. It was assessed in 2002 as EN A1acd+A2acd in the Colombian Reptile Red Book (Castaño-Mora 2002). The species has also been listed in Appendix II of CITES since 1975, as are all other species in the genus. It was assessed again in 2015 as CR-E in the Colombian Reptile Red Book (Morales-Betancourt et al. 2015).

Colombia prohibits the commercial exploitation of this species, as well as the collection of its eggs or hatchlings, by Resolution 0219 of the Ministry of Agriculture in 1964. Also, Resolution 126 by the Executive Directorate of the Regional Autonomous Corporation of the Magdalena and Sinú Valleys in 1965 declared a closed season, prohibiting the sale or purchase of this species on a national scale. However, these legislative acts have not been accompanied by effective implementation programs and they remain largely unenforced. At present, there are no protected areas within the range of the species, so creation of a reserve where even subsistence hunting is regulated is clearly a top priority for this species.

Most management projects for P. lewyana focus primarily on nest transfer and head-starting techniques (Páez et al. 2015b), and also usually include environmental education and community involvement programs. While nest transfer is obviously justified for populations that suffer nest loss each nesting season due to flooding caused by hydroelectic plant water discharges, the method, combined with head-starting, is probably not justifiable for other populations. Projection matrix analyses indicate that even with a 100% increase in egg and hatchling survival thanks to such management efforts, most populations would continue to decline at slightly lower rates. In contrast, efforts to reduce adult mortality via education campaigns with fishing communities, protection of nesting females on beaches, and other improvements to enforcement of legislation for protecting adults could reverse declines and permit population recoveries. 


Citation: Páez, V., Gallego-Garcia, N. & Restrepo, A. 2016. Podocnemis lewyana. The IUCN Red List of Threatened Species 2016: e.T17823A1528580. . Downloaded on 28 September 2016.
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