The Open Ocean exhibit at uShaka Sea World was transformed into a maternity ward this past weekend when a female thorntail ray (Dasyatis thetidis) gave birth to four healthy pups.
The 40cm-wide pups are miniature replicas of the adults. Each is born with a small, white round end to their barb, designed to protect the mother during the birthing process.
Rays are independent from birth and are designed to survive without food for several days before catching their own, so all that the aquarists needed to do was to keep a watchful eye on the quadruplets over the weekend. All four were reported to be in good health, able to swim effortlessly and deemed fit for release.
On Tuesday 19 September 2017, uShaka Sea World divers caught and gently lifted the pups out of their tank and transferred them to a specially equipped transport tank. They were then weighed, measured and given an overall health check before being released into the ocean.
Since January 2014 a total of 39 pups has been produced by two female thorntail rays in the Open Ocean exhibit. Of these, 36 were released within a few days of being born and the remaining three are doing well in the exhibit.
Although their biology is not well documented, female rays are known to give birth to their young close inshore. Since they are the preferred food of many ocean predators, particularly sharks, the pups spend some time in shallow waters to avoid predation.
Thorntail rays are one of the largest ray species occurring along the east coast of KwaZulu-Natal and are found both inshore and up to depths of 400m. They are occasionally caught by shore anglers.