Jenkins Whiprays ( Himantura jenkinsii) have a disc-shaped body with rounded edges that can reach up to about 70 cm across. They are usually greyish-brown with a white underbelly. Their long, whip-like tail features small spines rather than large spear-shaped thorns. The disc is mostly smooth, except for some small bumps. Their medium-sized eyes are positioned on top of their body, and behind these eyes are larger oval spiracles. These spiracles help the ray breathe by drawing water in and passing it over their gills for oxygen, even while the ray rests on the seafloor.
The ray uses electro-sensors called ampullae of Lorenzini to detect electrical fields produced by other marine organisms. This is especially useful for finding prey in dark or murky waters. By staying still and using these sensors, the Jenkins Whipray can pick up on the faint electrical signals from potential prey, making it an efficient hunter even when it appears to be motionless.
Behavior and Diet
Jenkins Whiprays can live up to around 25 years, though this can vary with environmental conditions. They are often found resting on the seafloor in shallow waters, where their stillness helps them blend in and avoid predators. This motionless behavior also allows them to use their electro-sensors to detect the electrical fields of nearby prey.
Their diet mainly consists of small fish and invertebrates. In dark or murky waters with poor visibility, they rely on their electro-sensors to locate prey. Once they detect potential food, they use their mouth to scoop it up from the sediment. Their smooth disc enables them to move efficiently across the seafloor while foraging.
Reproduction
Jenkins Whip Rays are ovoviviparous, meaning they give birth to live young that develop from eggs inside the mother’s body. The female carries the fertilized eggs internally, where the embryos are nourished by the yolk within the eggs. Once fully developed, the young rays are born as miniature versions of the adults. During reproduction, the male uses specialized claspers to grasp the female and transfer sperm. After fertilization, the eggs stay inside the female until the young are ready to be born, ensuring they are relatively advanced and ready to fend for themselves. It is believed that Jenkins Whiprays can reproduce multiple times a year, with estimates suggesting they might give birth up to six times annually.
Predators
The main predators of Jenkins Whiprays are humans and sharks. Highly valued for their large thorns, skin, meat, and cartilage, these rays are frequently caught intentionally and accidentally by coastal fisheries using tangle nets, bottom trawls, seine nets, and, to a lesser extent, longlines. Due to the high intensity of regional fishing activities, especially in Southeast Asia, the International Union for Conservation of Nature (IUCN) has classified this species as "Vulnerable."
Where to Find the Jenkins Whipray on Koh Tao
The Jenkins Whipray can be found at the following dive sites around Koh Tao:
Aow Leuk,
Tanote Bay,
Hin Wong Bay,
Laem Thian,
Twin Peaks.
They can also be spotted during deep dives at the HTMS Sattakut wreck.
