Scientists now have access to the visual world of animals, including the life and death struggles of hunters.
This is the first time that knowledge on the structure of the eyes of tiger sharks has been combined with images of prey and habitat from small cameras. The development of a virtual visual system for the shark was enabled by this.
The tiger sharks were tagged with small video camera tags by an international team of scientists. A virtual visual system was used to process the videos from the tags to understand how sharks see sea turtles.
The movement sensors on the video tags allowed for the monitoring of the shark's reaction to turtles.
The first study to look at animal camera footage through the visual capabilities of the animal they are mounted on allows researchers to gain a truer representation of life.
When watching the raw camera footage of tiger sharks approaching sea turtles it seemed strange that often tiger sharks swam directly over a turtle sitting on the reef, a potentially easy meal.
When looking at the visual system of the tiger shark, it is extremely difficult to detect the turtle, and when they remain motionless, it can allow them to camouflage themselves from attack.
Humans and video cameras have higher visual acuity than tiger sharks. The sharks have to rely on the sea turtles to identify them. Sea turtles' best defence from attack may be to remain still in the presence of the predator.
The researchers were able to observe the swimming behavior of the sharks because of the fine-scale movements they were able to track.
A change in tiger shark behavior was accompanied by the visual detection of a turtle, showing that vision is still important for these animals. The sharks slowed down and performed a lot of turns after a sea turtle was spotted.
"The picture that emerges through the eyes of the shark is one of almost slow motion pursuit of a slow moving prey, rather than a high speed ambush that we tend to think of when we see other big predator in action, such as white sharks," says co-author Dr.
The sharks have to be careful not to spend too much energy chasing prey to make a meal in environments that are not very rich in vitamins and minerals.
The study shows how tiger sharks and sea turtles use visual clues to find their prey. The approach could be applied to other species.
Few researchers have taken the next step to really consider the videos they provide in terms of what the subject animals can actually see. The next frontier in this form of tagging is this one.
More information: Laura A. Ryan et al, Prey interactions in tiger sharks: Accounting for visual perception in animal-borne cameras, Journal of Experimental Marine Biology and Ecology (2022). DOI: 10.1016/j.jembe.2022.151764 Journal information: Journal of Experimental Marine Biology and Ecology
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