A team of researchers studying the reproductive biology of tiger sharks has captured some incredible footage inside a mother shark’s womb. The pregnancy scan was carried out at Tiger Beach in the Bahamas as part of conservation work.
In their latest expedition in December 2019, the group, led by Dr Neil Hammerschlag, the Director of the Shark Research and Conservation Program at the University of Miami, and Dr James Sulikowski, Professor and associate director in the School of Mathematical and Natural Sciences at Arizona State University, caught five tiger sharks to carry out “pregnancy check-ups” on.
The area, nicknamed “Tiger Beach” due to the presence of the tiger sharks, first caught Hammerschlag’s attention over concerns that human behavior was impacting the movements of these huge fish. Scuba divers feed the sharks in the bay all year round in order to offer tourists the chance to swim with them.
However, the increase of tiger shark numbers in the cold months could also be attributed to another reason. With a 9:1 female to male ratio of the sharks spotted in the bay, their reproductive behavior was brought into question.
Speaking to IFLScience, Dr James Sulikowski described his entrance into the project: “Dr Neil Hammerschlag’s work at Tiger Beach came upon some unique questions that could only be answered through an understanding of shark reproductive biology. Since that is a specialty of mine, he contacted me (back in 2011) and we have been working together ever since on this and many other sharky projects.”
Together, they have been studying the abundance of pregnant tiger sharks in the bay via ultrasound scanning, blood sampling for hormone analysis, and tagging for further tracking of the pregnant sharks' movements. Previously, if you wanted to know anything about the reproduction of these large predators you would have had to cut them open. However, Sulikowski and Hammerschlag’s work leaves the animals completely unharmed.
Before they carry out the tests they first have to catch the sharks and hold them close to the boat, which can prove quite a challenge when they’re the largest predatory fish in the tropical sea. But the results are worth it as the researchers can use the information gathered to determine the reproductive state, cycle and length of gestation for the animals, as well as tracking their movements to reveal possible gestation and pupping grounds. All of which is crucial for the management and conservation of the species.
Not only does the team have the task of catching the sharks, but the weather does not always prove to be plain-sailing either. “When you think of the Bahamas, you think sunny skies, white sand, and blue water. However, strong winds, big waves, rainstorms, and other factors can make sampling impossible,” Sulikowski told IFLScience.
When they successfully make it out onto the water, Dr Sulikowski uses ultrasound imaging coupled with a VR style headset to instantly look at the sharks in the womb.
“One of the major achievements of this trip was finding tiger sharks in different gestation stages,” said Sulikowski, “It was so cool to see baby tiger sharks at different sizes!”
However, this is not the last time we will see the incredible footage captured by the scientists, as "more trips to tiger beach to learn more about this amazing species" are planned for the future.