It’s hammer time!

Don’t expect 1990s rapper MC Hammer to be dancing up a storm in his drop-crotch pants singing U Can’t Touch This. Forgive me for putting that little ditty in your head but since last week I haven’t been able to get it out of mine. This inspiration is not because of flashbacks from my “big hair, don’t care” New Jersey upbringing; it is a shark that has me singing that tune.  

Last week a hammerhead shark was seen on Nantucket. A video that went viral captured images of it hunting in the shallows at a local beach. It was not an isolated incident. There have been more than 40 reports of sharks on Nantucket beaches this season.  

Also this week on our Island, South Beach lifeguards reported sharks on multiple occasions and closed that beach for a few hours. While the South Beach sharks were not definitively identified as hammerheads, it is a likely supposition when you consider the reports from that other island.  

Hammerheads are not common in our waters. They prefer more tropical areas but are not unheard of, either. With warmer water, these sharks can and do move into more northern areas in their pursuit of prey. They are fond of eating fish, crustaceans and mollusks, so hammerheads have been known to migrate and munch as far north as Maine. Given the increase in water temperatures resulting from climate change, we may see more of these sharks in the future.  

It makes sense to be aware of your surroundings and watch for sharks while at the beach, though panic is not necessary. It is rare that hammerheads attack humans. The Florida Museum reports that since 1580 there have been 17 documented attacks on humans — and none of them were fatalities.  

Which is not to say that you want to go head to head with these sharks. Nor could you, since this species’ hammer-like head (called a cephalofoil) can be three feet across. The big head, like a hammer, is a multi-function tool. It can serve as a weapon, hammering prey, and help these animals navigate, find food and swim hydrodynamically.    

On each side of that cephalofoil, there is a single eye. That pair of eyes allow for 360-degree vision in the vertical frame. Hammerheads can see above and below, and have increased binocular vision and depth of field because of that placement.  

These fish are viviparous, giving birth to live young once per year. Different species have differing numbers of offspring, with the birthing of up to 30 little hammerheads possible. These mini mallets must fend for themselves — and they do, in their natal groups. The offspring take care of themselves since there is no parental care after birth.  

Sharks are elasmobranchs, a subclass of fishes that are cartilaginous (rather than bony), so only their sharp, triangular teeth will remain after they die and their softer parts decompose. Hammerheads can live up to 30 years, though their fossilized choppers can persist long after.  

Make no bones about it; these sharks can hold their own, and should be given wide berth. It brings us back to MC Hammer (cue the “you can’t touch this” refrain). He wasn’t singing about this species but his message is relevant. Parachute pants may be out, but so should be entering the ocean when hammerheads are about.

Suzan Bellincampi is islands director for Felix Neck Wildlife Sanctuary in Edgartown and the Nantucket Wildlife Sanctuaries. She is also the author of Martha’s Vineyard: A Field Guide to Island Nature and The Nature of Martha’s Vineyard.