Creepy Cookiecutter Sharks

There are two species of Cookiecutter Shark; Isistius brasiliensis and Isistius plutodus. They are found in warm waters surrounding the equator, especially around islands and in deeper waters of up to 1000m. They are make vertical migrations towards to surface at night and it is at this time that they are thought to make contact with most of their prey (Stevens, 2013).

Image: Sourced from noaa.gov [Accessed 16 May 2014]

Image: Sourced from australianmuseum.net.au [Accessed 16 May 2014]

Cookiecutter Sharks are considered ectoparasitic, and feed on a wide variety of large marine animals including sharks, squid, whales, dolphins, seals, pelagic fishes and in more recent reports, deceased and living humans (Gallo-Reynoso & Figueroa-Carranza, 1992). The Cookiecutter Shark gets its name from its characteristic feeding behaviour. Large eyes on this animal show that it is very much a visually oriented predator. The shark uses a combination of muscles in the upper jaw and fleshy lips to suck onto prey, and then cut out a circular plug of flesh using their sharp upper and lower teeth. The result is literally a circular cutout of the prey’s flesh, and is the signature attack remnant of this animal’s feeding technique. Failed attempts result in crescent shaped lesions in the prey (Hoyos-Padilla et. al, 2013).

A recent article by Hoyos-Padilla et. al (2013), described the attack of a Cookiecutter shark on one of the ocean’s leading predators, the Great White Shark (Carcharodon carcharias). The observation was made off the coast of Isla Guadalupe, home to a large population of a variety of seals, which in turn attracts large numbers of Great White Sharks. Waters off this coast can drop to depths of up to 3,600m, with temperatures of 18 - 22°C, it provides an ideal location for the residence of Cookiecutter sharks. Divers involved in a cage diving operation took photos of a subadult male white shark displaying the characteristic bite mark of a Cookiecutter. Directly adjacent to the bite mark, a crescent shaped scar can be seen, suspected as a failed attempt at a bite by the Cookiecutter shark. This attack shows the broad range and the daring attacks made by Cookiecutter sharks. This photo is the first known photographic evidence of an attack on a Great White Shark by Cookiecutters (Hoyos-Padilla et. al, 2013).

Image: Sourced from Hoyos-Padilla et. al (2013) journal article: Observation of an attack by a Cookiecutter Shark (Isistius brasiliensis) on a White shark (Carcharodon charcharias) [Accessed 16 May 2014]

In 2011, the first documented attack on a live human being was reported in Hawai’i. This attack was an unprovoked incident, and involved a 61 year old Caucasian man who was completing a long distance swim across the Alenuihāhā Channel. This distance was a 47.5 km swim, and takes approximately 16-20 hours to complete. A kayak and support boat, complete with first aid and emergency communication, accompanied the swimmer. The attack took place at approximately 8.00pm, and was thought to have been caused by the presence of Purpleback Flying Squid (Sthenoteuthis oualanisnsis). The squid were attracted to the swimmer due to the navigation lights on the support kayak, which was paddling in a 1 meter proximity of the swimmer. Squid were so close to the swimmer that on several occasions the man was bumped by the animals. Purpleback Flying Squid are a known target prey of the Cookiecutter shark, and not long after making contact with the squid, the man felt a sharp pain on his chest. He swam directly to the kayak, and during his attempt to get into the kayak; he felt a second pain in his leg.

Image: Sourced from Honebrink et. al (2011) journal article, First Documented Attack on a Live Human by a Cookiecutter Shark (Squaliformes, Dalatiidae: Isistius sp.) Image (a) shows the failed bite attempt on the chest, image (b) shows the successful bite mark on the calf, 7 days after the incident.

The man survived the attack, but the injury required a skin graft and many weeks of healing. This was not the first reported attacked on a human, however it is the first on a live human. The particular shark responsible was suspected to be Isistius brasiliensis, due to previous sightings in the area. Cookiecutter shark bite marks have been suspected in two incidents that were reported to the International Shark Attack File (ISAF). Both attacks were on deceased humans, the first a man who was found after going missing from a fishing trip, and the second on a suicidal female who was found 6 days after being pronounced missing (Honebrink et. al, 2011).

These incidents were both considered as scavenging events, showing that Cookiecutters are just as likely to scavenge as they are to attacking live prey.

References:

Gallo-Reynoso, J.P., Figueroa-Carranza, A.L. (1992). A Cookiecutter Shark wound on a Guadalupe Fur Seal male. Marine Mammal Science. 8(4): 428 – 430. Doi: 10.1111/j.1748-7692.1992.tb00060.x

Honebrink, R., Buch, R., Galpin, P., Burgess, G.H. (2011). First Documented Attack on a Live Human by a Cookiecutter Shark (Squaliformes, Dalatiidae: Isistius sp.). Pacific Science. 65(3): 365 – 374. doi: 10.2984/65.3.365

Hoyos-Padilla, M., Papastamatiou, Y.P., O’Sullivan, J. Lowe, C.G., (2013) Observation of an attack by a Cookiecutter Shark (Isistius brasiliensis) on a White shark (Carcharodon charcharias). Pacific Science. 67(1): 129 – 134. doi: 10.2984/67.1.10

Stevens, J. (SSG Australia & Oceania Regional Workshop, March 2003) 2003. Isistius brasiliensis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2.