PSY 2364 Animal Communication. Elk (Cervus canadensis) Extra credit assignment. Sad Underwing (Catocala maestosa) 10/11/2017

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1 PSY 2364 Animal Communication Elk (Cervus canadensis) Kingdom: Phylum: Class: Order: Family: Genus: Species: Animalia Chordata Mammalia Artiodactyla Cervidae Cervus canadensis Extra credit assignment Sad Underwing (Catocala maestosa) Extra credit assignment (up to 5%). Optional extra credit assignment on a topic of your choice (topic must be cleared with instructor). Submit proposed extra credit topic (one paragraph) via elearning by Wed Oct 18. Report due on the same day as the final exam (Dec 13). Sad Underwing (Catocala maestosa) Copperhead (Agkistrodon contortrix) 1

2 Copperhead (Agkistrodon contortrix) Copperhead (Agkistrodon contortrix) Vision Visual systems have evolved to detect light. This requires trapping the electromagnetic energy and absorbing it by a receptor molecule. This process triggers an electrical response in the receptor neuron. Visual systems Vision provides a means of detecting objects in an animal s surroundings. Luminance (intensity differences; brightness) Reflectance (spectral composition; color) Vertebrate visual systems contain two types of receptors: Rods are more sensitive in low light conditions Cones function in daylight and provide the basis for color vision Vision Visual systems have evolved to detect light. This requires trapping the electromagnetic energy and absorbing it by a receptor molecule. This process triggers an electrical response in the receptor neuron. Brightness (intensity) Hue (dominant wavelength or frequency) Chroma (degree of saturation or purity of the dominant frequency) Properties of color 2

3 Rods and cones Cone cells in the retina contain a pigment derived from a protein (opsin) linked to a small molecule called retinal. The pigment absorbs light energy (photons) which activates retinal neurons, generating action potentials in the optic nerve. Two different wavelengths of light can produce the same pattern of activation in a cone cell. The outputs of the cone receptors are combined and must be compared at a higher level of the visual nervous system. result from a decoding of the outputs of the color receptors by the brain. in birds, lizards, turtles and many fish is based on four types of cone cells (tetrachromatic color vision). These animals can distinguish colors in the near ultraviolet range of the spectrum. Old World primates and humans have three color receptors; most mammals have only two types (dichromatic color vision). Goldsmith TH (2006). What birds see. Sci. Am Evidence suggests that the progenitors of mammals lost two of the four types of cone cells during a period in their evolution when they were mainly nocturnal (and color vision was less important for their survival). Goldsmith TH (2006). What birds see. Sci. Am African monkeys, apes and humans reclaimed a third cone through duplication and subsequent mutation of the gene for one of the remaining pigments. Goldsmith TH (2006). What birds see. Scientific American

4 Outside Readings Pigments Pigments are chemical compounds whose molecules selectively absorb certain light wavelengths (mostly short wavelengths; yellow, orange, red) E.g., carotenoids, melanins, porphyrins Structural coloration Many animals use structural coloration rather than pigments. These involve microscopic surfaces that interfere with visible light, sometimes in combination with pigments (e.g. the iridescent colors of peacock s tail feathers) Structural coloration Ultraviolet / blue colors often involve coherent scattering (using layered structures or gratings) to produce a narrow range of wavelengths Ruby-throated Hummingbird Further reading

5 Polarized light Trichromatic color vision In humans and related primates, color vision is based on three types of cone cells in the retina of the eye, each sensitive to a range of wavelengths of light. This diagram shows a plane linearly polarized EMR wave propagating from left to right. The electric field is in a vertical plane and the magnetic field in a horizontal plane. The electric and magnetic fields in EMR waves are always in phase and at 90 degrees to each other. Dichromatic color vision Most other mammals are dichromats (two color-sensitive cone receptors). Evidence suggests that the progenitors of mammals lost two of the four types of cone cells during a period in their evolution when they were mainly nocturnal (and color vision was less important for their survival). Dichromatic color vision Dichromacy occurs in humans when one of the cone pigments is missing and color is reduced to two dimensions (color blindness). Protanopia (no red receptor) Deutanopia (no green) Tritanopia (no blue) Tetrachromatic color vision Several groups of animals (birds, reptiles, fish) have four distinct types of cone cells in the retina, adding a cone type sensitive to wavelengths in the ultraviolet range. Ultraviolet sensitivity Bees, like humans, have three receptor types, although unlike humans they are sensitive to ultraviolet light, with loss of sensitivity at the red end of the spectrum. 5

6 Ultraviolet (UV) receptors in birds Fruits and berries often reflect UV light to advertise their presence. Eurasian Kestrels can see UV reflections in the scent trails made by voles. Ultraviolet (UV) receptors in birds Male Blue Grosbeaks with the most intense UV components in their plumage are larger in size, control a larger territory, and feed their offspring more often than other males. Goldsmith TH (2006). What birds see. Sci. Am Goldsmith TH (2006). What birds see. Sci. Am Source: Schaefer, Schaefer and Levey (2004) Trends in Ecology and Evolution Sexual deception by plants! Spectra of a blueberry Vaccinium sp. (peak in the UV part) and willowleaf cotoneaster Cotoneaster salicifolia (peak in the human red part of the spectrum) according to the colour perception of humans (a), birds (b) and bees (c). The colours do not represent the actual colour sensation of each group but rather serve as an approximation to illustrate differences in visual abilities. Solid black lines denote the spectral sensitivities of the four (birds) and three receptor types in bees and humans based on physiological measurements and behavioural tests resulting in models of colour vision [25 27]. If at least two receptors are excited by photons of a given wavelength, wavelength discrimination is possible. Vertical lines denote this range for each group. Chemical communication Hormones - chemicals that operate internally to facilitate communication between the brain and organs involved in growth, digestion, reproduction Chemical communication Pheromones - chemicals that operate externally to facilitate communication with other members of the same animal species (conspecifics). 6

7 Chemical communication Allomones - chemicals that are transmitted to the members of other species, such as predators and prey (skunks) Functions of pheromones (1) to defend a territory from conspecifics dogs use urine to mark territorial boundaries and track these markers carefully. (2) to promote aggregation examples: social insects like termites and ants use various messages to coordinate complex activities of the colony (3) to alert others to food sources ants lay scent trails leading to a food source that helps others find the food Functions of pheromones (4) to alert others of danger alarm pheromones are used to signal the presence of danger (fire ants) injured minnows emit a chemical from skin cells that causes others to disperse (5) sexual attraction widely used in mammalian courtship, sexual attraction and copulatory behavior. In many species of mammals, female animals emit a sexual attractant pheromone to indicate mating readiness chemical signals can trigger hormonal changes that stimulate ovulation and/or sexual maturation Functions of pheromones (6) coordination of parent-young interactions (in vertebrate animals) (7) there may even be pheromones that signal status in a dominance hierarchy within a group Types of pheromones Primer pheromones Produce gradual changes over time in receiver e.g., pheromones that stimulate release of hormones involved in reproductive functions Releaser pheromones Instantaneous effects e.g., pheromones that evoke specific behaviors (attack, retreat, movements and postures) Pheromones in insects Male silkworm moths travel up to 30 miles in response to the female sex attractant, following the pheromone trail in the air. 7

8 Pheromones Pheromones are volatile molecules which, when released into the air, form an elongated plume called an active space (Wilson, 1970). Pheromones The shape and the size of the active space varies depends on the molecular weight of the compound and the wind velocity (Robinson,1994). Modes of transmission Current flow (in air or water) Diffusion (movement along a concentration gradient) Movement of receiver toward source Sex attractant pheromones in moths When a male moth detects pheromone molecules emitted by the female, he begins to search for the point source. He uses wind direction as a method of orientation. This process is called anemotaxis. odor plume Source wind direction Pheromones as honest signals Zahavi (1975) suggested that pheromones may serve as honest signals and provide reliable information because they accurately reflect the signaler's ability or resources. Pheromones as honest signals Example: Female tiger moths pick their mate based on the amount of pheromone released. The chemical attractant is derived from plant toxins which protect the eggs and are transmitted to the female during mating. 8

9 Pheromones as honest signals Melonworm Moth (Diaphania hyalinata) Example: Male garter snakes chose females based on size. Larger females release more pheromones. The greater the amount of pheromone released from the female s skin, the more offspring were produced in the previous season. Hair pencil pencil 9