The sample of species eye colors being used includes information on 181 species of amphibians and 342 species of reptiles. Families from both classes will be included in the following list. Because information is sparse, all families with at least 5 species in the sample will be included.
Families of amphibians and reptiles (with at least 5 sample species) arranged in order of average eye darkness:
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None DARK-EYED
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.450 Front-fanged Snakes (5 species)
.361 Mole Salamanders (9 species) MID-RANGE
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.255 Aguanas (52 species)
.250 Newts (7 species)
.250 Alligators, Caimans (6 species)
.230 Harmless Snakes (124 species)
.183 Whiptail Lizards (15 species)
.179 Skinks (7 species)
.177 Lungless Salamanders (24 species)
.170 Vipers, Rattlesnakes (25 species)
.167 Semiaquatic Pond & Marsh Turtles (9 species)
.150 Anguid Lizards (5 species)
.150 Pythons (5 species) LIGHT-EYED
.135 Geckos (39 species)
.125 Boas (8 species)
.103 Leptodactylid Frogs (29 species)
.060 Tree Frogs (29 species)
.058 Crocodiles (13 species)
.050 Narrow-mouthed Toads (5 species)
.030 True Frogs (33 species)
.027 Toads (28 species)
.000 Spadefoot Toads (5 species)
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1. Amphibians and reptiles present a consistent picture of eye-darkness and feeding behavior with few exceptions. Almost all are light-eyed carnivorous predators that ambush rather than chase prey. Many have anatomical features that can be “spring-loaded” to allow for a sudden and decisive strike.
2. Of all orders of land vertebrates, for which I have eye color information, Anura, (frogs) is the one with lightest average eye darkness. Their behavior seems to fit my theoretical notions in every detail. [The simple theory that I have suggested is that light-eyed creatures can wait without moving and dark-eyed creatures can move without waiting.] Frogs are skillful ambush hunters that mostly sit and wait for prey to come near. Their coiled tongues allow for a decisive and sudden first strike. They are primarily visually oriented. Their defenses against predators are mostly passive rather than active fleeing. Many frogs feign death as a form of passive escape. They lie on their backs with legs extended or folded next to the body. [I am not sure what else I could ask of them.]
3. The only family in the list to compete with families of frogs as lightest-eyed is the crocodile family. Crocodiles, too, are known for their ability to wait without moving and for the explosiveness of their sudden attack.
4. Of the five families of snakes, the three lightest-eyed families are less active than and depend more on ambush to get food than is true of the two darker-eyed families. The lighter-eyed families of snakes also use passive defense more than do the darker-eyed families.
5. Based on a very small sample, species of front-fanged snakes tend to have very light eyes or very dark eyes (similar to the case with owls). Two of the five species in the sample have yellow eyes and two have black eyes. They are more slender than are vipers and more actively seek prey. The coral snakes are members of this family.
6. The other family of this list with average eye-darkness in the mid-range are the mole salamanders. They spend much time underground in situations with no light. Such animals tend to have darker eyes than do their close relatives that depend more on vision to locate food.
7. Of the families of lizards, the lightest-eyed, geckos, are almost completely carnivorous and stalk prey. The darkest-eyed family, iguanas, have some species that include considerable vegetation in their diets.
8. Finally, in terms of average eye-darkness of the families, mobility, methods of obtaining food, and methods of defense or escape, amphibians and reptiles are totally different from another group we have reviewed, passerine birds. Whereas amphibians and reptiles have little sustained mobility and use skillful waiting to obtain food, that lifestyle is almost totally absent in the huge order of passerine birds. Their lifestyle is based on mobility. That can be said of some other orders of birds and mammals as well.
June 30, 2006
Large Families of Amphibians and Reptiles
IRISPIGMENTATION.COM
