BIEB 166 Lecture 22 (WI13)

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University of California - San Diego
Biol/Ecology, Behavior, & Evol
BIEB 166
James Nieh

Lecture 22 Conspicuousness - Controlled by several discrete factors Ambient light (A) - Amount of light in the environment - Certain wavelengths predominate in many habitats due to selective absorption and/or scatter. - Animals should avoid producing colors that are missing in the available spectrum because the result will be black ○ Aquatic habitats often lack red light ○ Terrestrial habitats affected by sun angle, weather, and vegetation ○ Forest light is green, dawn/twilight is purple, clouds produce grey, fog produces white veiling light Rayleigh scattering in water - As we go deeper in the water, less light is available - Increasingly when we go deeper, only blue light is available - Differential absorption of photons influence the amount of ambient light available - Reflects blue light in deep water - Reflects lots of other light (yellow, green, red, blue, orange) in shallow water (a lot of ambient light in shallow water) Terrestrial Habitats - Large gap, large amount of very bright white light from the sun Spectrogram - Wavelength VS amplitude - Forest shade sunny day, looks green - Woodland shade sunny day, looks blue-grey - Cloudy day, white light available - Mie scattering Reflectance (R) - Properties of the signaler's surface Background (B) - Trees, ground, sky - The conspicuousness of the signaler depends on its contrast with the background - Signalers can exploit any one of the four signal properties to maximize contrast Frigate birds - Epiphenomenon Males - With bright red color (sac) ○ Help transmitting sound to a further distance (sound monopole) ○ Visual signal in addition to the acoustic signal - Occupy the nest to attract females - Competitions with other male - Attack the other males Females - Strong male ○ Quality of the nest site ○ Gigantic red balloon 1. Optimal signal hue Habitats Available light Background hue Optimal signal color Night Low (gray) Black White, bioluminescence Marine High (blue) Blue Red, yellow reef -Tropical -Still have other -Contrasting wavelength environment photons -If the background is one end of the spectrum, you'd like to be the other end of the spectrum Tropical Medium (green) Green Red forest -Depend upon -Opposite color of the the density of spectrum trees Sand due High (white) Orange Blue-green -Nothing is -Brownish orange, -lizards filtering out but brown is not a the light color in the spectrum Sky High (white) Blue Black -Light intensity of the sky is much higher than the marine reef 2. Hiding from the background a. Brightness contrast ○ In dark environments, use light color or white ○ In bright light habitats use dark colors or black b. Hue contrast ○ Hue: dominant frequency of a color c. Movement contrast ○ Walk back and forth ○ Imitating the motion of leaves and branches in the environment ○ Minimize the movements of the animal and the movement of the leaves around d. Pattern/shape contrast ○ Pattern  Patterns evolved to help the animal to hide to its background  Nicely blend into their backgrounds  Some patterns make the animal to stand out of the background  Pattern contrast works depend upon the background it is in ○ Shape enhancement  Enhance the shape with outlining  Easy to see the shape (outline) is actually enhanced  Natural selection ○ Shape concealment  Disruptive pattern  Hide its shape  Predators look for hands and legs  Coloration makes it able to hide their features Tiger - Stripes breaking up the tiger to make it blend into the background Video Transmission Transmission - Transmission of visual signals through the environment - Transmission from signaler (Q ) Rr the background (Q ) B ○ Represent a mathematical function which is equal to the spectrum (curve) Female robin on the ground looking at the male robin sitting on the tree - Background: green - Male: bright red breast color Transfer function - A, R, B, and Q are expressed in a series of spectra whose shapes are determined by transfer functions at each step - F(A) = transfer function of A ○ This is what the animal actually sees - The transfer function of light from signaler to receiver depends on the size of the signal, the distance between them and the beam attenuation coefficient of the medium - Glare from the sun affects how clear the animal can see the other animal (signaler) ○ V = direct light from sun 1. F
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