Ask Dr Dazza: Tiger sharks and the infamous ‘shark arm case’
By Marine Biologist Daryl McPhee
Along with bull sharks and white sharks, tiger sharks (Galeocerdo cuvier) are one of the three species most frequently implicated in fatal bites on humans. Recently, an archaeological investigation in Japan revealed the discovery of a fatal series of bites from a tiger shark on a victim 3000 years ago.
Tiger sharks are the second largest predatory shark behind the white shark. The average maximum size of females is around 4m in length, although females up to 5m are recorded. Males are smaller with not too many over 3.5m, but that is still a big animal!
Where are they found?
The species is principally found in temperate and subtropical waters, but they also occur in temperate waters. They occur along the whole length of the Queensland coast and their habitat includes inshore areas such as Moreton Bay, offshore reefs, and deep waters to depths of at least 800m. Although rare, they are known to occur around the Redcliffe peninsula. They tend to be nomadic animals with water temperature and the availability of suitable food resources influencing their movements.
Tiger sharks have a large litter size for a shark species. Litter sizes can range from 10-80 pups, with 35 being the average. Tiger shark eggs hatch internally, and the pups are born live when they have fully developed. Tiger sharks have a method unique among sharks for nourishing their embryos which contributes to them being able to produce the large litter size. Breeding and pupping tend to occur in summer in Queensland, although females do not breed each year.
What do they eat?
Tiger sharks have very strong and distinct sideways pointed serrated teeth. This dentition is adaptable for consuming an extremely wide variety of prey, but particularly adept at consuming hard bodied prey such as marine turtles, which are one of their main sources of food. Tiger sharks are the main predator of adult marine turtles. Tiger sharks also consume dugong and dolphins. In a Queensland study, dugong remains were found in the stomach of 15 out of 85 animals examined. They also eat rays and other sharks and a variety of seabirds.
They are known as being the garbage cans of the ocean due to the wide variety of things that they have been known to eat. They capture live prey as well as scavenge on a variety of dead animals and other items. They have been known to eat metal and leather objects, tyres, and hard plastic items. Tiger sharks are principally nocturnal feeders, and their eyes have specific adaptations to low light environments.
The "Shark Arm Case"
The tiger shark was involved in one of the more infamous Australian criminal cases – the so called “Shark Arm Case”. In 1935, a large tiger shark was captured off Coogee Beach in NSW and transported to a nearby ocean aquarium for display. Very soon after being on public display, the shark regurgitated a human arm that had a distinctive tattoo. The tiger shark had eaten a smaller shark which had consumed part of missing person James “Jim” Smith, a known criminal and police informant who most likely had been murdered by a criminal associate and his body dumped at sea and scavenged by sharks. This incident even became the inspiration for an episode of CSI Miami!