Relationship between multiple paternity and reproductive parameters for Podocnemis sextuberculata (Testudines: Podocnemididae) in the Trombetas River, Brazil

Genetic studies of multiple paternity are a valuable tool to gain information on the reproductive biology of turtles. We analyzed paternity type in Podocnemis sextuberculata and related number of fathers per nest to nesting period (beginning, middle, or end of nesting season); clutch size (number of eggs); female size; and hatchling success. Females were captured and maximum linear carapace lengths measured during the 60 days that encompass the nesting season at Rio Trombetas Biological Reserve (Pará, Brazil). Nests were marked and blood samples collected from hatchlings. Six heterologous loci were used: five from Podocnemis unifilis and one from Podocnemis expansa. Hatchlings were analyzed from 23 nests, and the rate of multiple paternity was 100%. The mean number of fathers per nest was six (± 0.9), and no significant difference between number of fathers in a nest and nesting period. Similarly there was no significant relationship between number of fathers in a nest and female size or hatchling success rate. Number of fathers was, however, positively correlated with clutch size (Spearman correlation rho = 0.47; P > 0.05). To our knowledge, this is the first study to test the relationship between multiple paternity and ecological aspects of the reproductive ecology of turtles in the genus Podocnemis. © FUNPEC-RP

Vulnerability of giant South American turtle (Podocnemis expansa) nesting habitat to climate-change-induced alterations to fluvial cycles

A change in seasonal flooding cycles in the Amazon may negatively impact nesting success of the Giant South American Turtle (Podocnemis expansa). Our aim was to devise a technique that could be replicated in the entire Amazon basin, for monitoring alterations in fluvial cycles and their effects on turtle nest mortality. We mapped the spatial distribution and height of P. expansa nests and tested the effects of different inundation scenarios within the Trombetas River Biological Reserve, Para state, Brazil. We also used historical data on water level and hatchling production to test whether the sharp decline in the Trombetas River P. expansa population over the past thirty years was related to detected changes in the flood pulse. Our models indicate that an increase of 1.5m in the water level is sufficient to decrease the time of exposure to less than the minimum required for incubation and hatching (55 days above the water) in 50% of the nesting area. This model explains the low hatchling production in dry seasons when the total nesting site exposure was less than 200 days. Since 1971, there was an average decline of 15 days per decade in sandbank exposure during the nesting season (a total of 62 days from 1971 to 2015). However, the decrease in sandbank exposure was not significantly correlated with the sharp decline in hatchling production. Changes to the water cycle in combination with the main sources of decline (overharvest, construction of dams, and dredging of riverbeds) might have an accumulative effect on P. expansa populations. © The Author(s) 2016

Abundance and population structure of podocnemis erythrocephala (Testudines, Podocnemididae) in the Unini River, Amazonas

We studied the population structure, sex ratio, and abundance of a locally endangered species of freshwater turtle, the red-headed river turtle (Podocnemis erythrocephala), in the Unini River in Negro River Basin in Brazil with capture-recapture of marked individuals in 1 yr, including both dry and rainy seasons. We used trammel nets of 3 different inner mesh sizes in the lakes. The nets were revisited at 3-hr intervals from 0600 to 1800 hrs each day. All turtles were released after being marked, measured, and sexed. During the study, 352 individuals were marked including 162 males, 150 females, and 40 immatures. The majority of the turtles (79%) were captured in the dry season when the water level of the river was declining. Mean ± standard deviation straight-line carapace length was 210 ±14 mm(range 163-262 mm) for males and 251 ±18 mm(221-303) for females. Most turtles captured were in the intermediate size classes: 200-210 mm for males and 230-270 mm for females. The sex ratio of adults in this population was 1.05 males per female, not significantly different from 11. Only 12 turtles were recaptured, each once: 5 males, 5 females, and 2 immatures. The population showed recruitment and the adults are in equilibrium; however, few turtles were captured in the smallest or largest size classes. © 2014 Chelonian Research Foundation

Sound communication and social behavior in an amazonian river turtle (Podocnemis expansa)

The social behavior of turtles during the nesting season can be attributed to a series of functions such as reducing predation, increasing hatchling survivorship, and information exchange between nesting females. However, the mechanism(s) used to remain in a group during the different phases of nesting behavior has yet to be explained. The objective of this study is to document the sounds produced by Giant South American River Turtle, Podocnemis expansa, during the nesting period, and identify how acoustic mechanisms might facilitate social behavior and group aggregation during this period. From September 2009 to October 2011, the sound repertoire of P. expansa was identified during the nesting period, which begins with the migration of the turtles from the flooded forests to the nesting beaches and terminates when the hatchlings emerge and the females migrate with the hatchlings to the flooded forests. Sounds were recorded when the turtles were active in different behavioral patterns (1) migrating; (2) aggregating in front of the nesting beaches before basking; (3) nesting at night; (4) waiting in the water without nesting or after they have nested; and (5) waiting for the arrival of the hatchlings. We observed six types of sound in the recordings of turtles made during the nesting period. These data indicate that this species is social, and that sound plays an important role in the synchronization of the activities of groups during the nesting season. © 2014 by The Herpetologists' League, Inc