Ace Your Animal Science Project by Robert Gardner

Author:Robert Gardner [, ]
Language: eng
Format: epub
ISBN: 978-1-4645-0491-4
Publisher: Enslow Publishers, Inc.
Published: 2010-03-12T05:00:00+00:00

FIGURE 14: Within 7 m (23 ft), an owl never missed its prey by more than one degree, even in total darkness. At 7 m, an error of one degree is only 12 cm (4.8 in).

Interestingly, the owl seemed to know its limitations. If the sound made by the “mouse” was more than 7 m away, the owl would land slightly short of the mouse and then wait until it heard another sound before pouncing.

To find out how an owl strikes its prey, Payne took movies. First, he filmed an owl with the lights on. His movies showed that after an owl heard the mouse, it turned to face the sound, leaned its head forward, and pushed off from its perch. The owl made one stroke of its wings and then glided straight to the mouse. As it approached its prey, the owl suddenly moved its feet forward from beneath its tail to a point under its chin. Then, just before striking, it pulled its head back and spread its claws.

Because humans have more difficulty walking a straight line in darkness than in light, Payne thought an owl might strike differently in darkness than in light. To film his owl in darkness, he used a sniperscope. A sniperscope is a device that can form images of objects from the infrared light (heat) they emit. The images appear on a screen similar to a small television screen. A movie camera can be used to take pictures of the screen every 1/24 second. Payne found that in darkness the owl flapped its wings several times, flew more slowly than in light, and swung its feet back and forth as it moved.

Payne reasoned that the owl on its perch hears the sound coming along a different path than the path its feet must follow to reach the mouse. Figure 15a shows how the two paths differ. To place its ears and feet along the same path leading to the prey, the owl leans forward to hear the sound. This places the bird’s ears and feet on the same straight-line path to the mouse (see Figure 15b). Just before it strikes, the owl swings its feet forward and its head back. This places its feet along the path its ears were following and its ears back where its feet were.

An owl’s foot has four talons that cover a rectangular area (see Figure 16). To grasp a mouse most effectively, the owl should be moving across the mouse’s path when it strikes (see Figure 17) so that its claws reach across the mouse’s back. Payne’s movies showed that the owl would often turn 90 degrees just before striking the mouse. And it would do this even in darkness. But how can an owl in total darkness know which way a mouse is facing?

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.