Perceptual and Motor Skills, 1991, 73, 1033-1034. O Perceptual and Motor Skills 1991

EYE COLOR AND FEEDING BEHAVIOR OF ANIMALS ' MORGAN WORTHY

Georgia Slate University

Summary.-A theory is presented of a systematic relationship between iris pigmentation and feeding behavior of land vertebrates.

A relationship between eye color and feeding behavior that remains consistent across different types of animals was suggested some years ago (Worthy, 1975). The purpose of this note is to present a brief, up-to-date summary of the methodology and theory that evolved from that idea. Published information on eye color has been collected to create a data base for more than five thousand species of amphibians, reptiles, birds, and mammals. For each report (e.g., each subspecies or locality), the lightest eye color mentioned is scored as follows: "Light" (blue, green, yellow, orange, and white) = 0; "Medium" (red, hazel, light brown, and grey) = .5; "Dark" (brown or black) = 1. These are averaged to give a measure for each species, and, in turn, these are averaged to give a measure of eye darkness for each family or whatever taxonomic group is being studied. A study of families of birds (Worthy, 1978), using a two-point scale of eye darkness and "blind" ratings of behavior made by ornithologists, indicated that light-eyed birds were more deliberate and dark-eyed were quicker. Using the three-point scale and an enlarged data base including all classes of land vertebrates, a more complete pattern of eye darkness and feeding style emerged as shown in Fig. 1. Averape Eye Darkness

Feeding Behavior

Light (Less than .33 on eyedarkness scale)

Hunting by ambush or stalldng

Midrange (.33-.67 on eyedarkness scale)

Foraging, scavenging, or swimming underwater to feed

Dark (More than .67 on eyedarkness scale)

Hunting by direct pursuit

FIG. 1. A theory of relationships between eye color and feeding behavior in families of animals

'Address correspondence co M Worthy, Counseling Center, Georgia State University, University Plaza, Atlanta, GA 30303

Light-eyed families (or other taxonomic groups) hunt by ambush or they forage; dark-eyed hunt by direct pursuit or they forage; those in the midrange of eye color seem to lack the ability needed to hunt by ambush or by direct pursuit and so feed by means of foraging, scavenging, or swimming underwater. The best ambushers are light-eyed animals such as frogs, snakes, crocodiles, herons, and cats. The best at hunting by direct pursuit are darkeyed animals such as swifts, swallows, insectivorous bats, and weasels. Examples of animals in the midrange of eye darkness that illustrate the model are (some) turtles, crows, penguins, fruit bats, and monkeys. Within a single order, the pattern is illustrated by light-eyed hawks that use surprise to ambush prey, dark-eyed falcons that use direct pursuit to catch prey, and medium-eyed vultures that feed on carrion. These relationships are probably mediated by physiological differences in the central nervous system, such as levels of neuromelanin, that influence speed of motor reactions (Hale, Landers, Snyder-Bauer, & Groggin, 1980). The pattern is also reflective of an evolutionary trend seen in land vertebrates in that birds and mammals, in general, tend to differ from amphibians and reptiles in having darker eyes, being more mobile, and depending less on tactics of ambush to get food. REFERENCES HALE,B. D., LANDERS, D. M., SNYDER-BALER, R., & GROGGIN, N. L. (1980) Iris pigmentation and fractionated reaction and reflex time. Biological Psychology, 10, 57-67. W O R ~ YM., (1975) Eye color and comparative psychology. Paper presented at the Southeastern Psychological Association convention, Atlanta.

WORTHY,M. (1978) Eye color, size and quick-versus-deliberate behavior of buds. Perceptual and Motor Skills, 47, 60-62.

Accepted November 27, 1991.

Eye color and feeding behavior of animals.

Perceptual and Motor Skills, 1991, 73, 1033-1034. O Perceptual and Motor Skills 1991 EYE COLOR AND FEEDING BEHAVIOR OF ANIMALS ' MORGAN WORTHY Georg...
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