ZOO-ology column: The Night Shift
Nov. 20, 2011 at 5:20 a.m.
By Judie Farnsworth
You step into the dark night, eyes blinking as they strain to see.
Your head turns, listening for sounds and you jump at the sudden snap of a branch. The senses you depend on during daylight hours seem to have deserted you.
Some animals are naturally active at night. You might say they work the night shift. That's when their "jobs" are available. With bodies suited to this way of life, they wake from their daytime rest with finely tuned senses - the built-in tools of the nighttime trade.
We use flashlights or headlights, but nocturnal animals come equipped with their own. There are a group of mirror-like cells near the retina called the tapetum lucidum, meaning bright carpet. Light bounces from the retina to the tapetum where it reflects back to the retina for the greatest use of any available light. The glowing eyes we see at night are caused by light being re-directed from the reflective tapitum.
Nocturnal animals often have large eyes with higher numbers of light sensitive cells called rods and fewer color sensitive cone cells. Color isn't as important in a darkened world.
They may have pupils in a slit shape that open and close more quickly and tightly than a round pupil.
The sense of smell may be finely tuned at night. There is often less wind at night and scent particles stay in the air, making them easier to recognize and follow.
Some animals, especially snakes, have well developed Jacobson's organs - highly sensitive scent receptors. The snake's tongue flicks out, picking up scent particles and deposits them in two openings in the roof of the mouth where the receptors are.
Others animals, like coyotes or wolves have a sense of smell hundreds of times sharper than humans.
We would need special equipment to hear a mouse walking through grass. Some animals have super powered hearing apparatus that detect and sort sounds.
Even the arrangement of feathers on an owl's facial disc helps direct sound to the ear openings. Lack of sound is also significant. Owls have fringed feather edges that lessen wind resistance, allowing silent flight. A mouse doesn't hear the owl coming until it's too late.
Bats use echolocation to find night flying insects. They send out ultra sonic sound that bounces off objects giving information about location, size and shape.
Whiskers give an animal an extended sense of touch for its job in a darkened world. Whiskers are usually at least the width of the animal's body. If the whiskers won't fit through an area - whoa - neither will the body. Animals like raccoons have an exceptional sense of touch. They are able to locate food in the dark water of a pond at night.
The night shift isn't all that spooky if you understand what's going on. It's the unknown that gives us the jitters.
The Texas Zoo will present Creatures of the Night, a program for children ages 7 to 11 from 6:30 to 8 p.m. on Nov. 29.
Call The Texas Zoo at 361-573-7681 for more information and to pre-register.
Judie Farnsworth is a longtime volunteer at the Texas Zoo specializing in educational programs.