Foraging mode proceeded from herbivorous prey to active predator to ambush predator. Activity time proceeded from diurnal to polyphasic to nocturnal. Relative-risk ratios were computed for having a circular, subcircular, or vertical-slit pupil relative to having a horizontal pupil as a function of foraging mode or diel activity. Multinomial logistic regression tests were conducted with foraging mode, activity time, and pupil shape as factors and genus as a covariate. ( C) Results of statistical tests on the relationship between foraging, activity, and pupil shape. The dots in each bin have been randomly offset to avoid overlap. Colors represent diel activity: yellow, red, and blue for diurnal, polyphasic, and nocturnal, respectively. The axes are pupil shape and foraging mode (herbivorous prey, active predator, or ambush predator). ( B) Pupil shape as a function of foraging mode and diel activity. From top to bottom: vertical-slit pupil of the domestic cat, vertically elongated (subcircular) pupil of the lynx, circular pupil of man, and horizontal pupil of the domestic sheep. Horizontally elongated pupils create sharp images of horizontal contours ahead and behind, creating a horizontally panoramic view that facilitates detection of predators from various directions and forward locomotion across uneven terrain. This is advantageous for ambush predators to use stereopsis to estimate distances of vertical contours and defocus blur to estimate distances of horizontal contours. Vertically elongated pupils create astigmatic depth of field such that images of vertical contours nearer or farther than the distance to which the eye is focused are sharp, whereas images of horizontal contours at different distances are blurred. Species with horizontally elongated pupils are very likely to be prey and to have laterally placed eyes. Species with vertically elongated pupils are very likely to be ambush predators and active day and night. Duplication for commercial use must be authorized in writing by ADAM Health Solutions.There is a striking correlation between terrestrial species’ pupil shape and ecological niche (that is, foraging mode and time of day they are active). Links to other sites are provided for information only - they do not constitute endorsements of those other sites. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. This site complies with the HONcode standard for trustworthy health information: verify here. Learn more about A.D.A.M.'s editorial policy editorial process and privacy policy. is among the first to achieve this important distinction for online health information and services. follows rigorous standards of quality and accountability. is accredited by URAC, for Health Content Provider (URAC's accreditation program is an independent audit to verify that A.D.A.M.
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