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Differentiating Male and Female Batagur baska (River Terrapin) - Chris Tabaka DVM

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This CITES I species is one of the more intriguing as well as mysterious in the chelonian world.  While there are a wide array of in situ breeding programs in countries such as Malaysia, Cambodia, and Thailand, not much is known about the wild habits of these  animals other than their nesting beach preferences.  The pictures below were taken at one of the in situ breeding facilities in Malaysia. 

 

 

 

 

Hordes of Batagur                         Dr. Hugh Quinn with Batagur

There are three different methods that can be utilized to sex Batagur depending on the age of the specimen in question.  The following techniques are broken down according to each of these age classes.

 

Adults

 

Adult animals are the easiest by far to sex.  Note the iris coloration in the following animals.  The male has whitish to light yellow irises while the females are a dull brown.  These iris color changes start taking place at around five years of age in captive specimens (Murray, pers comm). 
Male Batagur baska Female Batagur baska

 

One to Five year olds

 

Animals between one year of age and five years of age can also be readily sexed.  For these age classes, the primary difference lies in the position of the cloaca on the tail as well as a few other  secondary differences.

 

Note not only where the cloaca opens in the male pictured on the left below (cloaca opening is at the edge of the marginals) but also the round appearance to the cloaca as well as the almost straight line appearance to the caudal marginal scutes as they run perpendicular to the length of the tail.   In the female on the right, note that the cloaca opens well before the marginals, the elongated appearance to the cloaca along the length of the tail, and also the more rounded appeareance to the caudal marginal scutes. 

 

Male Batagur baska Female Batagur baska

 

Again, note these differences, particularly the position of the cloacal opening in the tail,  in the side by side comparison in the animals pictured below.

Hatchling to one year olds

 

After sexing the older specimens above, by far the most intriguing sexing differentiation I have ever seen in a chelonian species is that it appears possible to sex Batagur baska  specimens STRAIGHT OUT OF THE EGG.  While at this facility, we had the rare opportunity to examine numerous hatchlings including many still with externalized yolk sacs/curved lateral marginals (1-2 days post hatch)  as well as some animals which we dug up from a recently hatched nest.  In each of these animals, there were decided differences that make me believe that this species is able to be externally sexed from day one.

 

The technique for this is very straightforward.  Place the animal upside down on your palm.  Gently pull the tail caudally.  Exert the same amount of pressure for each animal that you are sexing so that consistency can be maintained.  Examine the cloaca closely for the following differences. 

 

Note the cloacal opening in the animal on the left below.  Even with the gentle rearward pressure, the cloacal opening shape is still maintaining a circular appearance.  If you look closely, you can see that the opening actually appears to be forming a line perpendicular to the length of the tail and parallel to the caudal edge of the marginals.  Now take a look at the animal on the right.  In this case, with gentle pressure, the cloacal opening is very obviously elongated parallel to the length of the tail. 

 

Male Hatchling Batagur baska Female Hatchling Batagur baska

In the overexposed picture below, again note the differences between the two animals.  Each is having identical degrees of pressure exerted on the tail.  Note the roundish opening of the male on the left as well as the elongated cloacal slit along the length of the tail in the female on the right


  

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