The Northern River Terrapin Batagur baska counts among the world’s rarest turtle species. Genetic research contributes to increasing the population in a conservation-oriented breeding facility.
A few years ago, a working group led by Professor Uwe Fritz of Senckenberg Dresden, together with the Austrian turtle expert Dr. Peter Praschag, studied the relationships among Southeast Asian turtles. Some of the samples also came from “Batagur” Terrapins. The carapace of this river terrapin can reach an impressive length of 60 centimeters – and it ranks near the top of the Red List as acutely threatened with extinction.
Hitherto unrecognized species in the south
At that time, the species Batagur baska was assumed to range from Eastern India across Bangladesh, Myanmar and Thailand to Cambodia. However, genetic data were only available for southern specimens, and the much rarer northern animals had already been given up on, since all conservation efforts were concentrated on the south. Peter Praschag discovered a few “Batagur” Terrapins at local meat and fish markets in Bangladesh and was able to export samples to Europe. He noticed that these animals differed morphologically from those found in southern regions. The males have a black head and neck, and during the mating season, the lower neck and the extremities take on a deep red hue. In contrast, males from the southern regions show a solid black skin all over.
The genetic analyses in Dresden revealed that the animals from northern regions represent the original species B. baska (Praschag et al. 2009), and that the southern animals belong to a previously unrecognized species, B. affinis. All facts collected to date considering the “Batagur” Terrapin refer to representatives of the southern species; therefore, little is known about the actual species Batagur baska (the Northern River Terrapin) – except for the fact that excessive egg collecting, the destruction of its nesting beaches and consumption of the animals by humans had pushed them to the brink of extinction in the past 100 years. The northern species almost faded quietly into oblivion, since it was believed that it was identical with the southern species, whose conservation all efforts were concentrated on.
Captive breeding to save the species
Once the Northern River Terrapin had been recognized as its own species, rapid steps toward its preservation were required due to its acute risk of extinction. The Tiergarten Schönbrunn zoo in Vienna and Peter Praschag bought 14 males and 6 females at local markets and from private persons who kept the animals in ponds in Bangladesh as good-luck charms.
Initiated by the Tiergarten Schönbrunn, the “Project Batagur” conservation breeding station was established in Bhawal National Park north
of Dhaka, the capital of Bangladesh. Initially, the animals were randomly paired, which led to the first breeding success: In the year 2012, 24 young hatched from the eggs, followed by 63 in 2013. While this approach quickly increases the number of individuals, the breeding project’s long-term goal is the preservation of genetic diversity, which requires the selection of partners not closely related to each other. To create the basis for this approach, blood samples from all of the animals were sent to the Senckenberg laboratory in Dresden.
Genetic fingerprint for the preservation of diversity
Based on genetic markers, so-called microsatellites, the relationships between the animals can be determined. The method works similar to the genetic fingerprint that is used in human genetics and criminology. Microsatellites are short DNA segments with a recurring motif. Mutations can cause changes in the number of repetitions of this motif, and therefore the “fragment length” of the respective DNA segment. An animal may show two different fragment lengths in such a segment, which is also known as a locus, since the nuclear genome consists of a maternal and a paternal copy. By examining a large number of microsatellite loci and using a computer-aided analysis, it is possible to decipher the relationships, equivalent to a paternity test in humans.
With the aid of 14 microsatellite loci we were able to show that most of the adult Northern River Terrapins were only distantly related to each other. This is a good starting point for continued breeding and the preservation of the genetic diversity within the species. Using the same method, we were also able to determine the parents of the young animals that hatched during the breeding program – an important prerequisite for establishing a “breeding book” for the “Batagur” project and for avoiding the pairing of closely related animals. In the process, we also learned some new information about the species: We discovered that the young in one nest came from different fathers, which means that the mother must have mated with several males. This is of great advantage for breeding, since it potentially increases the fertilization rate and leads to a higher genetic diversity in each generation.
In 2013, fishermen in Bangladesh caught three young Northern River Terrapins in their nets, which indicates that there are at least a few surviving females in the wild. To find and protect wild terrapins and their nesting grounds is of the highest priority. In early 2016, egg shells were found on a beach where the species used to occur. After repeated attempts we managed to extract useable genetic material from the shells. However, the genetic analysis unfortunately revealed that the discovered egg shells did not belong to B. baska but to the sea turtle Lepidochelys olivacea, which apparently nests in the same river delta. A setback, but we continue our search, since each single individual of this impressive species is important for its preservation.
earned her Bachelor of Science in Biology with an emphasis on Genetics at the Technical University of Dresden. With her Master’s studies at the University of Rostock, she specialized in the field of evolutionary biology. In 2013, she came to the Senckenberg Natural History Collections in Dresden to work on her Master’s thesis. From 2014 to 2016, she served as a scientific volunteer in Professor Fritz’s working group, studying the speciation processes of various turtle species, primarily with the use of genetic procedures. At the same institute, she is currently pursuing her doctoral thesis about the phylogeography and population genetics of two South African turtle species.