When you think of sharks with weird-shaped heads, you probably think about the hammerhead shark first. If you look up “Sharks with weird-shaped heads,” most of the results are about hammerheads. No one talks about the smallest of the hammerhead species, bonnethead sharks. For hammerheads, the average length for a female is 15-18 feet, and a male is usually 12 feet. Even though hammerheads and bonnetheads are from the same family called Sphyrnidae, bonnethead sharks are usually only 36-48 inches (3-4 feet) in length with the max being 59 inches.
Unlike hammerhead sharks, bonnethead sharks have a more rounded head shape, which is more similar to a shovel instead of a hammer. The scientific species name for them is “Sphyrna tiburo”. According to Vocabulary.com, a Sphyrna tiburo is a “small harmless hammerhead having a spade-shaped head”.
Due to their size and their shy nature, they are considered harmless to humans. On the Florida Museum website, it is stated that bonnethead sharks are often caught in different traps such as shrimp trawls and longlines. These sharks aren’t targeted for any purpose but when caught their meat is used for human consumption. The Florida Museum also states that “Although it is marketed, this species is of little economic importance. Recreationally, bonnetheads can provide great sport on light tackle or fly fishing gear.” The World Conservation Union has categorized this species as “Least concern” due to the high population.
A couple of things make this species so interesting such as the dimorphism between male and female, and the ability for females to give birth without a male. Firstly, usually, there are only a few ways to tell female and male sharks apart. Dimorphism is when two sexes of the same species have differences, such as length, shape, coloring, etc. For most sharks the only dimorphism is size, females are usually larger, and claspers, which is an extra flap on the back of the pelvic fin on males. However, it is unknown if any sharks have dimorphism on their heads, except for the bonnethead shark. Male bonnethead sharks have a noticeable notch on the back of their head. On females, this area is rounded and not at all bulged out.
Next, we come to the topic of parthenogenesis, otherwise known as virgin birth. There are only four shark species that virgin birth has been recorded and those are white-spotted bamboo sharks, blacktip sharks, Zebra sharks, and bonnethead sharks. You might have heard of this from the stingray, Charlotte, who gave birth recently without a male in the tank. Charlotte’s birth went viral on social media, with people saying she was the mother Mary of stingrays. Little to people know this is actually pretty common.
These sharks are so fascinating, but hardly anyone knows about them. These sharks deserve more recognition for the things they do for science and for learning the biology of sharks. They help teach people about dimorphism when it comes to sharks, and are teaching us about pathogenesis. Hardly anyone knows that pathogenesis exist, and these sharks help not only bring attention to it but also help us understand it. Bonnethead sharks are simply fascinating.
