Tuesday, April 16, 2013

Manō Kihikihi

They are easy to identify … and their name tells you what to look for (their body and head shape resemble a hammer, when viewed from above (or below.))

Marine organisms generate an electric field around their body; some believe the shape of the hammerhead's head allows electro-receptive organs in the animal to have increased sensory abilities - a beneficial quality when searching for prey.

In addition, the head shape may aid in their movements, providing lift or possibly a smaller turning radius.

Since sharks are ‘apex predators’ at the top of their food chain, they may influence the population structure of species lower in that food chain.

The sharks are found in warm and tropical waters, worldwide from 46° north to 36° south.  They can be found down to depths of over 1,600 feet, but is most often found above 80-feet.  During the day they are more often found close to shore and at night they hunt further offshore.

The scalloped hammerhead, one of the most commonly seen hammerhead sharks in Hawaiʻi, generally reaches between 5 to 10-feet in length - adults are usually found in the open ocean, often around seamounts or outer reef slopes.

Most fish hatch from eggs outside the females' bodies, but hammerheads, as well as other sharks, are born alive - the shark babies are called 'pups.'  As the pups grow, they spread out, forming schools that feed on the bottom at night.  At maturity, the young sharks head offshore.  (Scott)

Kāneʻohe Bay, Oahu, Hawaii, is a pupping and nursery ground for the scalloped hammerhead shark and hammerhead shark pups are the most abundant top-level predator in the bay.  (Lowe)

Females travel to shallow, protected waters in the spring and summer months to give birth.

Between April and October, adult hammerhead sharks enter Kāneʻohe Bay, deliver 15 to 30-pups about 20-inches long, mate and then leave.  (Scott)

It is estimated that as many as 5,000-10,000-shark pups are born in Kāneʻohe Bay each year and that the pups remain in the bay only 3-4 months after being born.  They eat small fish and crustaceans.

Young hammerheads graze along the bay floors, mostly at night. As the youngsters grow, they gradually move to the mouths of the bay and eventually join their relatives in the deep water.  (Scott)

Adults occur singly, in pairs, and in small schools while young scalloped hammerhead sharks live in large schools.  It is thought that male and female scalloped hammerheads may segregate during certain times of their life history.  (ufl-edu)

Hammerheads are among the majority of sharks whose attacks on people, if they happen at all, are defensive in nature. Almost all sharks will show an aggressive display if cornered, as will most animals.  (pbs)

Though hammerheads are not usually aggressive, they should be considered potentially dangerous.

The image shows a hammerhead shark.   In addition, I have added other images in a folder of like name in the Photos section on my Facebook and Google+ pages.

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