Researchers have always suspected that sharks, like many other fish, return to their original birthplace to give birth themselves. Now they have hard evidence.

Salmon, as well as other fish, tend to return to their original birthplace because their young are slow-maturing, and need a safe place devoid of predators in order survive. The phenomenon is known as natal philopatry.

Analysis of mitochondrial DNA – which is passed directly from mothers to their children – also shows that sharks in different families give birth in different places.

But for hard proof, scientists had to track a single shark all the way from birth to motherhood. A team of researchers from the US, Canada, the Bahamas and Saudi Arabia rose to the challenge. Their initial findings were published online just last Thursday in the journal, Molecular Ecology.

The scientists began tagging and sampling baby and “toddler” lemon sharks in 1995.

By 2008, the scientists thought it might be the right time for the oldest individuals to return to the original nursery. They used nets and ropes to capture these mothers-to-be and took DNA samples to see whether they were the original study participants. (Some sharks still had their transponders.)

They eventually captured two sharks. One of them had been enrolled in the study in 1995, when she was estimated to be two years old. A few months later, they captured a baby shark that DNA showed to be her offspring. The baby was captured less than 2,5 miles from where the mother had been tagged 13 years earlier.

Study lead author Kevin Feldheim of the Field Museum of Natural History in Chicago:

A study like this comes around once in a great while. As long as we can continue funding the field and lab work, I hope to keep going for another 20 years.

[Source : YouTube, LA Times]