Tiger sharks can eat anything — from dolphins, other sharks, sea turtles to rubber tires and other ocean trash, hence, nicknamed as the garbage cans of the sea. But recently, scientists discovered by analyzing the DNA of a shark’s barf that baby tiger sharks have a different diet. They documented that baby tiger sharks eat songbirds (such as sparrows, woodpeckers, and doves), and not the usual sea birds (seagulls or pelicans).
Kevin Feldheim, one of the co-authors of the study and led to the DNA analysis of the shark’s diet, said that “if these sharks with their tigerlike stripes see an easy target or meal, they will undoubtedly go for it.” But, he was shocked to learn that they’re eating songbirds. He added that this is one of the awesome projects since the discovery of DNA profiling.
Researchers from Mississippi State University studied the tiger sharks’ diet. They wrassle the 3 foot long sharks onto a boat, pump the shark’s stomachs, and examine the sample of its stomach contents. Don’t worry; no sharks are harmed in the process and were released afterward. Shockingly, out of the 105 sharks they’ve examined, 41 had bird remains in their stomachs.
However, it was difficult for scientists to determine what bird species the tiger sharks’ digested. As a solution, the team sought assistance with the Field Museum’s Pritzker Laboratory for Molecular Systematics and Evolution to analyze its DNA.
The team took the bird remains and used chemicals to break them down their primary molecular components. Then, they analyzed the DNA sequences found in the bird’s tissues. Afterward, they compared them to the available databases of bird’s DNA to know what species they are.
“We found out that none of them were seagulls, pelicans, cormorants, or other types of marine birds. They were all terrestrial birds that usually live in our backyards,” said Marcus Drymon, the paper’s lead author.
Moreover, this is not the first time that tiger sharks are known to eat birds. In Hawaii, some adult tiger sharks haunt baby albatrosses who are just learning to fly, says Feldheim. But this is the first time that we acquired scientific evidence that tiger sharks eat songbirds that usually live on land.
Feldheim added that the sharks hunt on songbirds since its easy to prey due to the species’ difficulties in traveling over the ocean. During migration, they’re exhausted, and sometimes they fall into the sea during a typhoon. Also, terrestrial birds are more appealing than seabirds because seabirds can handle themselves better in the water compared to songbirds.
What is the impact of this study?
It proves the importance of having DNA databases, which should be available for scientists. DNA can tell something that observation cannot.
Also, this study gives us a better understanding of tigers sharks. This information can somehow help us to protect them. According to Feldheim, all sharks currently facing some severe problems. We still don’t know how industrialized fishing affected them, but most of the top predator populations are continuously declining.
Although tiger sharks are notorious for being man-eaters, we humans pose a more significant threat. Based on National Geographic, most populations of tiger sharks are harvested for their fins, skin, and flesh. Their livers are a good source of vitamin A, and usually, it is processed into vitamin oils. In general, sharks take a long time to mature sexually and have low birth rates. Their population may also suffer due to overfishing. As of today, they are included in the near-threatened list of species.
Sharks are known to be the top predators, and they are essential in keeping the oceans in balance. They prey on the weak and prevent the potentially harmful fish populations from taking over a particular ecosystem. They are at risk of accumulating too many toxins from the prey they eat.
For example, plastics break down into microplastics — which are eaten by small fish. But these microplastics further break down into toxins that stay in the fishes’ system. This can cause sufficient harm to sharks if they’ve eaten it over time.
What can we do to help save sharks?
We need to stop buying shark products. We need to raise awareness that just like us, sharks are just living their own lives. They are acting like police offers, regulating the rules set by Mother Nature.
If sharks disappear in the world’s oceans, there will be negative consequences. Without them, at the top of the food chain, some population of aquatic creatures may also decline and suffocating algae blooms will increase. These algae blooms create toxins and can ruin coral reefs. We must do our part to save these creatures from extinction.