Big sharks can also hunt each other.The evidence is presented in a study that speaks of the first documented case of the death of a pregnant female porbeagle shark.or porbeagle shark (Lamna nasus), possibly at the hands of a great white shark (Carcharodon carcharias), which is a larger predator.
Researchers from Arizona State University (USA) publish in Frontiers a study on this case of predation of the porbeagle shark, a threatened species according to the list of the International Union for Conservation of Nature (IUCN).
The witness to the death of the female porbeagle is a tracking tag placed by the teamwhich would have been ingested by the shark that devoured it and then excreted into the sea.
This is the first documented case of porbeagle predation anywhere in the world.according to study lead author Brooke Anderson of Arizona State University.
However, he warned that if this type of predation “is more widespread than previously thought, it could have significant repercussions for the porbeagle shark population, which is already suffering due to historical overfishing.”
In this case, not only was the reproductive-age female shark, which could contribute to population growth, lost, but also all of her developing offspring.
The porbeagle, an endangered species
Porbeagle sharks are large, active sharks that can reach 3.7 meters in length, weigh 230 kilos and live up to 30 years, although some specimens can double that age.
Females reproduce from the age of 13 and give birth to an average of four offspring every one or two years, a slow reproductive cycle that means this species cannot recover from the threats to which it is exposed.
In fact, the Northwest Atlantic porbeagle is listed as endangered on the IUCN Red List of Threatened Species, while the Northeast Atlantic and Mediterranean populations are critically endangered.
Satellite transmitters
The devoured female was one of those the team tagged with satellite transmitters as part of a migration study. The flipper-mounted tags send the location to satellites every time the female rises above the surface.
A second tag, called a PSAT, measures data such as the depth and temperature at which the animal moves. This type of tag falls off after a set period and floats to transmit the stored data to satellites.
Researchers hoped to obtain data from the 2.2-meter-long pregnant female to help identify important habitats for porbeagle mothers and their newborns.
PSAT began transmitting from Bermuda at 158 days, earlier than it should have been released, and data indicated the animal had spent most of its time submerged.
Eaten by a larger predator
However, for four days, the temperature and depth of the PSAT were constant and for the team there was only one explanation: the porbeagle had been hunted and eaten by a larger predator, which excreted the PSAT about four days later and began transmission.
Researchers are targeting two possible suspects large enough to prey on mature porbeagles and at that time of year: the great white shark (Carcharodon carcharias) or the common mako shark (Isurus oxyrhinchus), although various data made them opt for the first.
“The predation of one of our pregnant mako sharks was an unexpected discovery (…) but with technological advances, we have begun to discover that interactions between large predators may be even more complex than previously thought,” Anderson said.
The researcher believes that these interactions need to be further studied to estimate how often large sharks hunt each other, as this can help to discover “what cascading impacts these interactions could have on the ecosystem.”
Keep reading:
· Huntington Beach authorities have closed a section of Sunset Beach to the public following a shark sighting in the ocean
· Teenager loses part of leg after shark attack in Florida Keys
· VIDEO: 11-year-old boy managed to escape a shark attack in Florida