In the event of a shark attack, it's very important to determine which shark species was responsible, so authorities can take the appropriate measures. A new study indicates that readily available medical gauze can be used by first responders to obtain that information.
Ordinarily, investigators rely largely upon eyewitness descriptions and bite-mark characteristics to ascertain which shark species was involved in an attack. Descriptions can be very subjective and influenced by the trauma of the event, however, whereas bite marks may be distorted by factors like bite force, bite angle, and the material which was bitten.
That's where "transfer DNA" comes in.
When a shark bites an object such as a surfboard, a kayak-like surf ski, or a paddle board, it often leaves traces of its genetic material in the bite marks. Trained investigators can then use forensic-grade swabs to collect that material for subsequent DNA analysis, to see which shark species did the biting.
This information is crucial to safety efforts, as not all species attack humans for the same reasons. Additionally, some species are likely to just be passing through the area, while others may be permanent residents. And if shark-culling measures are instituted, it would definitely be a shame if the wrong species was targeted.
Unfortunately, though, neither the forensic investigators nor the specialty swabs are typically present right when and where an attack occurs. By the time the bite marks on the surfboard or whatnot can be professionally analyzed, the genetic material may have been washed off. That said, one thing that often is on-scene immediately after a shark attack is a first aid kit.
Led by Dr. Belinda Martin from Australia's Flinders University, a team of scientists recently set out to see if the plain ol' medical gauze included in such kits could be used by people like lifeguards for collecting transfer DNA. The researchers started by examining a surf ski that was bitten in an attack during an Australian surf ski race.
In this particular case, not only were there traces of DNA in the bite margin, there was also a relatively large piece of shark tissue left behind. Both forensic swabs and pieces of standard medical gauze were used to collect the trace material, which was then analyzed.
It was found that both DNA collection methods identified the culprit as a great white shark, which was confirmed by more definitive analysis of the larger tissue sample. There definitely was the potential for misidentification in this case, as a shark tooth found on the deck of the boat that retrieved the surf ski was from a different species.
In two subsequent attacks – one on a surfer and one on a surf skier – gauze-collection of transfer DNA from bites on both boards once again proved to be sufficient for identifying the assailant as a great white. In one of those cases, the gauze wasn't analyzed until 33 days after the attack occurred (although it was kept in a sealed container).
"We have shown that the use of gauzes, which is widely available and accessible, is a simple and effective alternative to forensic-grade sterile swabs," says Flinders' Dr. Michael Doane, co-author of the study. "Therefore, we encourage the use of gauze as a means for collecting DNA by first responders, including surf-lifesavers, police, and first aiders."
A paper on the research – which also involved scientists from the New South Wales Department of Primary Industries, and the Queensland Department of Agriculture and Fisheries – was recently published in the journal Forensic Science International: Genetics.
Source: Flinders University
