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Threat Level: low
The Bonnethead Shark is also known
as bonnet hammerhead,
bonnet shark, bonnethead shark, bonnetnose shark, and shovelhead.
- BONNETHEAD SHARK
Scientific Name.... Sphyrna Tiburo
Family Name...... Sphyrnidae
- General Information: The bonnethead shark is
a small hammerhead, and can be distinguished by its smooth, rounded,
Bonnetheads are the smallest species of the Sphyrnidae. The eyes
are located at the ends of the evenly rounded lobes of the flattened
head, rather than a hammer shaped. Also the head lacks a notch
at the midline. The pectoral fins are short and straight along
the rear margin.
- Size: The bonnetheads reach an average size
of 3-5 feet. The maximum recorded weight of a bonnethead is about
- Teeth: This shark has a remarkable dentition,
with small sharp teeth in the front of the jaw for grasping either
its mate or a soft-bodied prey, and broad molar-like teeth at
the back of the jaw for crushing hard-shelled invertebrates. Like
all sharks they have additional rows of teeth that are used as
the older teeth become lost or worn.
- Color: Its body is plain gray to gray-brown
and occasionally to a green tint above and shading to a light
- Feeding Habits: Bonnethead sharks feed daylight
hours and feeds primarily on invertebrates, crabs, shrimp, mantis
shrimp, snails cephalopods, as well as small bony fishes. Upon
locating a prey the bonnethead swims slowly within range, followed
by a quick acceleration to attack the prey. The prey is then crushed
in the molariform teeth. This differs from the capture event typically
of other sharks, where the jaws are initially closed and biting
ceases at jaw closure. This allows the bonnethead to take advantage
of prey that is not available to other species of sharks. After
the prey is crushed, it is moved by suction to the oesophagus.
- Senses: The bonnethead has a well-developed
sensory and nervous systems that allow them to be efficient predators.
Vision and hearing capabilities are exceptional as well as the
sensitivity of the lateral line to small vibrations, alerting
them to nearby potential prey.
- Social Behaviour: The behaviour of the bonnetheads
has been well studied. Some sharks exhibit specific types of behaviour
toward other sharks, including patrolling, head-shaking, jaw-snapping,
hitting, and hunching. It is believed that the function of this
behaviour is to establish and maintain dominance and other agonistic
relationships. Another example an individual bonnethead may swim
over top of another and "hit" the shark below it with
the edge of its head. The shark that was "hit" accelerates
off and often bears a slight contusion in the area where it was
struck. A study conducted on a captive colony of bonnetheads demonstrated
that this species forms linear dominance hierarchies, with the
size and sex of an individual determining its position in the
"pecking order". As the group swarm about their enclosure,
subordinate individuals would "give way" to dominate
specimens ( that is, they would change their course to avoid colliding
with the dominant shark ).
- Habitat | Migration | Distribution: Bonnetheads
are found in North Carolina to Brazil in the Western Atlantic
and from southern California to Ecuador in the Eastern Pacific.
This shark occurs in many different habitats within the temperate
and tropical waters of its range. It is abundant surf zone, bays
and estuaries, on coral and rocky reefs, and over sandy or muddy
bottoms. It also inhabits waters of the continental shelf to depths
of about 260 feet.
- Life Span: The life span of this species has
been estimated at 8-12 years.
- Reproduction: Bonnetheads are viviparous (giving
birth to live young) with a gestation period of four to five months,
which is the shortest gestation period of all other sharks. Females
reach sexual maturity when about 2 1/2 feet long. They retreat
to shallow bays and estuaries to give birth, in late summer or
early fall. Litter sizes average of 8 to 16 pups and each approximately
14 inches in length. During this time , the females lose their
desire for food, which prevents them from feeding on their pups.
Males move to a different location, also an adaptation to avoid
feeding upon their own young.
- Swimming: This species must swim continuously
so that its gills receive oxygen from the water, otherwise it
will sink. Bonnetheads swim continuously travelling long distances
following changes in water temperature.
- Bonnethead Shark Attacks: Considered harmless
to humans, this species is shy. There has only been one recorded
- Population Report: They are not endangered