The Brazilian Snake-Necked Turtle
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The Brazilian Snake-Necked Turtle Text and photos by REPTILIA 47 The Brazilian Atlantic trees had fallen creating a natural gap in the canopy). rainforest is considered On the other hand, recorded turtle body temperatures one of the most endan- are frequently higher than the water temperature, sug- gered ecosystems of the gesting that these reptiles have a physiological mecha- world (and a biodiversity nism for dealing with heat loss. hotspot), with native vegetation The dispersal rate of this sedentary species is extremely already reduced to only 5–10 percent low. Capturing and recapturing specimens showed a mean of its original area. In part, deforesta- daily displacement of only 2 meters, and it was not uncom- tion has been inevitable — the geo- mon to recapture a turtle at the same spot where it had been graphic range of this rainforest captured and marked 10 years earlier. This means that a encompasses areas of highest concen- given stream can have its own long-term turtle population. trations of human populations in It is well known that degradation and fragmentation of Brazil, with up to thousands of inhab- natural ecosystems has produced landscape islands. itants per square kilometer. Populations decline as the distribution area is reduced, and The Brazilian rainforest is topo- the resulting small, isolated populations are vulnerable to graphically complex, including areas of extinction. The Atlantic-rainforest home of Hydromedusa coastal lowlands, valleys, river systems, maximiliani has been continually disturbed by humans and mountains. Together with this alti- since the 16th century, resulting in a high degree of habitat tudinal gradient, the variation in tem- fragmentation. perature and rainfall cycles across the Furthermore, the topography of this area is complex, vast rainforest extension results in The Brazilian snake-necked turtle Hydromedusa maximiliani is a shy reptile species with hundreds of ridges and valleys drained by river and numerous distinct habitats with partic- stream systems. Thus, the turtle’s sedentary behavior, ular environmental conditions. In turn, their movement is limited to only a few turtles inhabit large rivers or lagoons habitat fragmentation by deforestation, and natural topo- this variety of habitats supports a great meters a day. In addition to their nat- with clay bottoms and turbid water. graphic barriers all contribute to limiting gene flow diversity of plant and animal species, urally sedentary lifestyles, freshwater On the contrary, Hydromedusa between turtle populations inhabiting different streams, many of which are endemic — among turtles may have geographical distrib- maximiliani lives in streams with even within the same watershed. Such factors must be them, the Brazilian or Maximilian’s utions in complex landscapes that fur- sandy and rocky bottoms and clear taken into consideration for the development of manage- snake-necked turtle, Hydromedusa ther restrict dispersal. This is the case water, normally with small waterfalls. ment and conservation programs. maximiliani (Mikan, 1820). of the rainforest dwelling Maximilian’s Hydromedusa maximiliani is one of Hydromedusa maximiliani feeds on a plethora of aquat- Marine turtles and some podocne- snake-necked turtle. the smallest Brazilian freshwater tur- The tranquil stream flow may be broken in places by small waterfalls ic invertebrates that it finds in streams, including small crus- midid river turtles (e.g., the Arrau Hydromedusa maximiliani is endem- tles. The carapace reaches a maxi- In some areas of Atlantic rainforest, the population den- taceans (shrimps and crabs), and insect larvae (mayflies, side-necked turtle, Podocnemis ic to eastern and southeastern Brazil mum length of only 198 millimeters; sity and biomass of Hydromedusa maximiliani can be very dragonflies, caddisflies, stoneflies, beetles, and mosqui- expansa, and the Yellow-headed side- (in parts of southern Bahia, Minas the plastron, only 140 millimeters. The high, reaching more than 190 turtles and 40 kilograms per toes). This diet is complemented by terrestrial inverte- necked turtle, Podocnemis unifilis) are Gerais, Espírito Santo, Rio de Janeiro, weight is less than 530 grams. The river hectare, according to long-term research including brates that fall into the water, such as earthworms, cock- considered species with high dispersal and São Paulo states), with a distribu- male is larger and heavier than the intensive mark-recapture field studies. roaches, crickets, termites, and spiders, as well as verte- capability, but most Brazilian freshwa- tion always associated with mountain- female, and also has a larger tail and a The Atlantic rainforest is home to several poten- brates, such as small frogs, or carrion of larger animals. The ter turtle species are sedentary, and ous regions. Most Brazilian freshwater more concave plastron. Adult dorsal tial predators of this turtle, including the jaguar diet can vary with the availability of prey in different sea- coloration, of the carapace and the (Panthera onca), puma (Puma concolor), raccoon sons of the year. Observations reveal that this turtle extremities, is dark to light brown; the (Procyon cancrivorous), coati (Nasua nasua), and river searches for food in areas of slow-moving water, such as plastron and ventral surfaces of the otter (Lontra longicaudis). However, in more than a decade around fallen trees, or along the inside curves of river extremities are cream colored. of fieldwork in a preserved area of Atlantic rainforest, only bends. The turtle may remain virtually in one spot, moving Hatchling dorsal coloration is dark two turtles were found dead with typical signs of river otter only its long neck, from side to side, scouring the area of brown to dark gray; the ventral sur- predation, such as dilacerated head and forelimbs. stream bottom within its reach. This behavior continues faces of the extremities are cream col- Although predators could carry turtles far from streams, for about 40 minutes before the turtle, without leaving the ored as in adults, but the hatchling where their remains would be difficult to find in the rainfor- water, moves to another area of slow current. plastron is totally black. Individuals of est litter, it is likely that the cryptic coloration and secretive The long neck of Hydromedusa maximiliani (from which different ages are associated with dif- behavior of the turtles limits their susceptibility to predation. comes the common name snake-necked turtle) seems to be ferent habitats, in which their different Being a reptile, Hydromedusa maximiliani could used to lunge after agile prey (such as certain insect larvae). colorations provide the best camou- depend on sunlight to increase its body temperature for Also, the neck allows the turtle to stay in deeper water, flage. Adults are frequently found in daily activities such as searching for food, mating, and helping to protect it from predators. After being sub- streams where their lighter color and dispersal. However, the dense Atlantic rainforest merged for about 15 minutes the turtle can extend its long flatter carapace make them resemble canopy allows little sunlight to penetrate to the under- neck to reach the water surface with its nostrils for breath- river stones. Juveniles explore story and river. Moreover, as an aquatic animal, the tur- ing, even standing up on its hind limbs on the stream bot- (though not exclusively) areas close to tle faces loss of body heat to the water, especially tom if necessary. In addition, if the turtle falls over onto its the shoreline. Hatchlings are normal- because of its small size. River water temperature is back, a common occurrence when on land, it can use its The cryptic coloration of the turtle can be associated with differential habitat. Adults are frequently found ly found in areas with no flow, such as about 20°C (68°F) year-round, even during summer. long neck as a lever to right itself. in streams where their light color and flat carapace make them look similar to river stones. Hatchlings are flooded areas along the stream banks, Nonetheless, in more than a decade of studying this tur- Hydromedusa maximiliani activity depends greatly on black, and often found in shoreline areas with little flow and an accumulation of dead leaves. Juveniles also explore shoreline areas where dead leaves accumulate. tle, only once was an individual found basking (where environmental conditions, particularly rainfall and temper- REPTILIA 48 REPTILIA 49 This turtle is well camouflaged in the shadows (near the trunk under the leaf) The Atlantic rainforest in southeastern Brazil Close-up of the shy Hydromedusa maximiliani Forelimb, internal organs, and head eaten by predator ature. Many of the turtles may be September to January. It is during reports indicate Hydromedusa they reach a safer size. Not by coinci- Bibliography PRITCHARD, P. C. H. 1984. Piscivory found on hot humid days following a this period that the turtles can be maximiliani clutches consisting of dence, study of stomach contents ARGÔLO, A. J. S., and M. A. FREITAS. in turtles, and evolution of the long-necked 2002. Geographic distribution. Hydromedusa Chelidae. Symp. Zool. Soc. Lond. 52: nighttime rainfall, whereas few are most frequently captured, reflecting two or three ellipsoidal eggs. The revealed that the stomachs of speci- maximiliani. Herp. Review 33: 147. 87–110. found after a sudden decrease in tem- an increase in their activity. incubation period is estimated to be mens with carapace lengths of less DA FONSECA, G. A. B. 1985. The van- SOUZA, F. L. 1995. História natural do perature. Searching the same stream Hatchlings (with shells that have not 250–300 days. than 70 millimeters were full of food ishing Brazilian Atlantic forest. Biol. Conserv. cágado Hydromedusa maximiliani (Mikan during different seasons (e.g., January yet hardened, and carapace lengths Growth is slow for a long-lived more frequently than were the stom- 34: 17–34. 1820) no Parque Estadual de Carlos Botelho, SP, região de Mata Atlântica and July) confirms the association of less than 50 millimeters) are found organism such as a turtle, so long-term achs of larger specimens; and the inci- (Reptilia, Testudines, Chelidae).