Brazilian snake-necked turtle (Hydromedusa maximiliani)
|Size||Adult carapace length: 10 - 20 cm (2)|
Adult weight: 120 - 520 g (2)
The Brazilian snake-necked turtle is classified as Vulnerable (VU) on the IUCN Red List (1).
The Brazilian snake-necked turtle (Hydromedusa maximiliani) is among the smallest of the Brazilian freshwater turtles. Unlike other turtle species, Brazilian freshwater turtles have limited dispersal ability due to a sedentary lifestyle (moving as little as two metres per day) and the complex geographical environment in which they live (3).
The adult Brazilian snake-necked turtle has an oval-shaped carapace, with the male being typically larger, heavier and possessing a more concave underside and longer tail than the female (4). The species also has a distinctive long neck, from which the common name ‘snake-necked’ is derived, that allows the turtle to stay submerged in deeper water to avoid predation and to seize agile prey (3).
Interestingly, the colour of the Brazilian snake-necked turtle changes with age. The adult has a dark to light brown carapace and cream-coloured plastron, while the juvenile has a dark brown to grey carapace and cream-coloured underside. In contrast, hatchlings have a completely black underside. These colour changes are likely to be related to the different camouflage required in each of the distinct habitats occupied by adults, juveniles and hatchlings (3).
The Brazilian snake-necked turtle is endemic to a narrow region of the Atlantic coast of eastern and south-eastern Brazil. Its distribution is restricted to primary forests in mountainous areas above 600 metres in elevation (2).
The Brazilian snake-necked turtle inhabits shallow streams with clear, cold water, sandy or rocky bottoms and often small waterfalls. Different life stages of this species are associated with different habitats (3). The adult Brazilian snake-necked turtle is found mainly in streams, where it resembles a river stone due to its lighter colour. Juveniles of this species usually occupy areas around the shoreline, while hatchlings inhabit areas with no water flow at all (2).
As with many turtle species, the growth rate of the Brazilian snake-necked turtle is low, with recorded individuals gaining only around 100 grams in weight and 7 millimetres in size over 10 years of monitoring. The average life expectancy of the Brazilian snake-necked turtle is 100 years (5). Despite this slow growth, the population density of the Brazilian snake-necked turtle can reach extremely high levels, with in excess of 190 individuals per river hectare being recorded in some parts of its range (2).
Reproduction in wild populations of the Brazilian snake-necked turtle is not fully understood but it is thought that the breeding season lasts from September to January. Observations of increased activity at this time suggest that breeding may correspond with the rainy season. It is thought that the female Brazilian snake-necked turtle lays clutches of 1 to 3 eggs beneath leaf litter or between tree roots, with an incubation period of around 250 to 300 days (2).
The diet of the Brazilian snake-necked turtle varies with seasonal prey abundance; however, it feeds primarily on aquatic invertebrates such as insect larvae and small crustaceans in areas of relatively still water. It may also prey on terrestrial species that fall into streams, such as earthworms, termites, crickets and spiders, or even small frogs (3).
The Brazilian snake-necked turtle’s long neck allows it to stay in deep water to avoid predation. After being submerged for about 15 minutes, the Brazilian snake-necked turtle can extend its neck to reach the water’s surface with its nostrils, enabling it to breathe without having to reveal its whole body to predators. The long neck is also used to lever the turtle back upright if it should fall over onto its back when on land (3).
The Atlantic rainforest ecosystem inhabited by the Brazilian snake-necked turtle is at severe risk due to degradation, fragmentation and loss of habitat associated with development of agriculture and human settlement. Other impacts include developing tourism and pollution of both aquatic and terrestrial habitats (2).
The high level of habitat fragmentation, in addition to the sedentary lifestyle and complex landscape inhabited by this species, means that small, isolated populations are susceptible to extinction (3). However, at present, the extent of the threats to the Brazilian snake-necked turtle is not clear and requires further research (2).
Protected area status exists in several parts of the Brazilian snake-necked turtle’s range, including areas close to Rio de Janeiro and São Paulo. However, the threat of continuing deforestation and pollution remains in other areas. Conservation measures proposed include the creation of new protected zones and expanding protection on existing fragments of rainforest, especially in places of intense development (2).
Learn more about conservation in the Brazilian snake-necked turtle’s habitat:
Conservation International: Biodiversity Hotspots - Atlantic Forest:
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- Carapace: the top shell of a turtle or tortoise.
- Crustaceans: diverse group of animals with jointed limbs and a hard external skeleton, characterised by the possession of two pairs of antennae, one pair of mandibles (mouthparts used for handling and processing food) and two pairs of maxillae (appendages used in eating, which are located behind the mandibles). Includes crabs, lobsters, shrimps, woodlice and barnacles.
- Endemic: a species or taxonomic group that is only found in one particular country or geographic area.
- Incubation: the act of incubating eggs; that is, keeping them warm so that development is possible.
- Invertebrates: animals with no backbone, such as insects, crustaceans, worms, molluscs, spiders, cnidarians (jellyfish, corals, sea anemones) and echinoderms.
- Larva: immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.
- Plastron: the lower shell of a turtle or tortoise.
- Primary forest: forest that has remained undisturbed for a long time and has reached a mature condition.
IUCN Red List (November, 2011)
Rhodin, A.G.J., Pritchard, P.C.H., van Dijk, P.P., Saumure, R.A., Buhlmann, K.A., Iverson, J.B. and Mittermeier, R.A. (Eds.) (2009) Conservation Biology of Freshwater Turtles and Tortoises: A Compilation Project of the IUCN/SSC Tortoise and Freshwater Specialist Group. Chelonian Research Monographs No. 5, 026.1-026.6. Available at:
- Souza, F.L. (2005) The Brazilian snake-necked turtle, Hydromedusa maximiliani. Reptilia, 40: 47-51.
- Souza, F.L. and Abe, A.S. (1997) Population structure, activity and conservation of the Neotropical freshwater turtle, Hydromedusa maximiliani, in Brazil. Chelonian Conservation and Biology, 2: 521-525.
- Martins, F.I. and Souza, F.L. (2008) Estimates of growth of the Atlantic rainforest freshwater turtle Hydromedusa maximiliani (Chelidae). Journal of Herpetology, 42: 54-60.