Why the funny head?

Kajiura's research | Other ideas | Education

Kajiura's research

"Electroreception in juvenile scalloped hammerhead and sandbar sharks" by Stephen M. Kajiura and Kim N. Holland, The Journal of Experimental Biology (2002), also available as a PDF, or start with the HTML Abstract. Conclusion:

"Therefore, although the sphyrnid head morphology does not appear to confer a greater sensitivity to prey-simulating dipole electric fields, it does provide (1) a greater lateral search area, which may increase the probability of prey encounter, and (2) enhanced maneuverability, which may aid in prey capture."

"What's with the Hammer's Head?" interview with Dr. Stephen Kajiura on Bob McDonald's CBC RadioOne "Quirks and Quarks" (September 21, 2002). Kajiura investigated electroreceptive and hydrodynamic explanations. He found hammerheads had "orientation" toward simulated prey from a greater distance, and increased turning stability. Here's the containing page.

"How the Shark Got its Hammer Head" by Kathryn Phillips, The Journal of Experimental Biology (2002). Introduces Kajiura's electrosensitivity findings. Also available in PDF.

Juvenile hammerhead biting an electrode from the Hawaii Institute Of Marine Biology (3.7 MB)

Ananova article on Kajiura's article.

"Why the hammerhead shark's head is in the shape it's in," press release from the American Physiological Society, at whose meeting some of Kajiura's research appeared.

Electroreception in Hammerhead Sharks from Hawaii Institute Of Marine Biology, with a video of a juvenile hammerhead biting an electrode.

Hammerhead: the carpenter's shark? Speculation on it's purpose.

General: Bit on shark electroreception from National Geographic. Here is their page on sharks' six senses.

General: How Sharks Work by Tom Harris, from How Stuff Works, on shark senses.

Other ideas

"If I Had a Hammer" by R. Aidan Martin, ReefQuest Centre for Shark Research, Rodale's Scuba Diving (August 1993)

"In the final analysis, the hammerhead 'hammer' is a complex structure that probably serves more than one purpose."

"Head Turner: What's the point of the hammerhead's head if the hammerhead doesn't hammer?" by Adam Summers, with illustrations by Shawn Gould. Is it for rapid turning? (No.)

"Why the Hammer Head?" by Richard Martin, Science Frontiers (1989). Three suggestions.

"Origin and Evolution of the 'Hammer'" by R. Aidan Martin, ReefQuest Centre for Shark Research. Fascinating short piece. Apparently, genetic work shows that the"hammer" appeared "rather suddenly and fully formed," and then diversified—the giraffe started with a long neck! From Martin's Topics in Shark Biology.

Education

National Geographic has two Lesson Plans, geared for different ages:

• Grade 3–5: Does the Hammer Help? with links to a video of scalloped hammerheads swimming. (Not the best video; you want to see footage of them making turns, not going straight!)
• Grade 6–8: What's the Hammer For? A good lesson. Note that the link to ReefQuest Expeditions: Topics in Shark Biology has changed.