Azure A's List: Chordata

• There are two main types of bowers. One clade of bowerbirds build so-called maypole bowers, which are constructed by placing sticks around a sapling; in some species, these bowers have a hut-like roof. The other major bowerbuilding clade builds an avenue type-bower made of two walls of vertically placed sticks. In and around the bower, the male places a variety of brightly colored objects he has collected. These objects — usually different among each species — may include hundreds of shells, leaves, flowers, feathers, stones, berries, and even discarded plastic items, coins, nails, rifle shells, or pieces of glass. The males spend hours arranging this collection. Bowers within a species share a general form but do show significant variation, and the collection of objects reflects the biases of males of each species and its ability to procure items from the habitat, often stealing them from neighboring bowers. Several studies of different species have shown that colors of decorations males use on their bowers match the preferences of females.
• Uy and collaborators^[who?] have shown that mate-searching females commonly visit multiple bowers, often returning to the male several times, watching his elaborate courtship displays and inspecting the quality of the bower and tasting the paint the male has placed on the bower walls. Many females end up selecting the same male, and many under-performing males are left without copulations. Females mated with top-mating males tend to return to the male the next year and search less.
• In addition, many species of bowerbird are superb vocal mimics. Macgregor's Bowerbird, for example, has been observed imitating pigs, waterfalls, and human chatter. Satin Bowerbirds commonly mimic other local species as part of their courtship display.
• Bowerbirds have also been observed creating optical illusions in their bowers to appeal to mates. They arrange objects in the bower's court area from smallest to largest, creating a forced perspective which holds the attention of the female for longer. Males with objects arranged in a way that have a strong optical illusion are likely to have higher mating success. ^[12]

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• Cats, like dogs and many other animals, have a tapetum lucidum, which is a reflective layer behind the retina that sends light that passes through the retina back into the eye.
• In very bright light, the slit-like iris closes very narrowly over the eye, reducing the amount of light on the sensitive retina, and improving depth of field.
• As with most predators, their eyes face forward, affording depth perception at the expense of field of view. Field of view is largely dependent upon the placement of the eyes, but may also be related to the eye's construction. Instead of the fovea, which gives humans sharp central vision, cats have a central band known as the visual streak.^[2] Cats can see some colors, and can tell the difference between red, blue and yellow lights, as well as between red and green lights.^[3] Cats are able to distinguish between blues and violets better than between colors near the red end of the spectrum.^[4]
• A cat has about twenty-four movable vibrissae ("whiskers")
• The structure of the brain region (barrel cortex) which receives information from the vibrissae is similar to that found in the visual cortex which permits the cat to create a three dimensional map of its surroundings. This doesn't mean that sensing with vibrissae is a type of vision. It is still a touch sensation and environmental information is built up incrementally (in small steps).
• Vibrissae aid sensation and navigation. The upper two rows of whiskers are able to be moved independently from the lower two rows for greater precision during measurement. A cat's whiskers are more than twice as thick as ordinary cat hairs, and their roots are three times deeper in a cat's tissue than other hairs. They have numerous nerve endings at their base, which give cats extraordinarily detailed information about nearby air movements and objects with which they make physical contact.
• Whiskers also aid in hunting. High speed photography reveals that when a cat is unable to see its prey because it is too close to its mouth, its whiskers move so as to form a basket shape around its muzzle in order to precisely detect the prey's location.^[15][16] A cat whose whiskers have been damaged may bite the wrong part of its prey indicating that they provide cats with detailed information about the shape and activity of its prey.

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• Bitis gabonica, commonly known as the Gaboon viper, is a venomous viper species found in the rainforests and savannas of sub-Saharan Africa.^[1] This is not only the largest member of the genus Bitis,^[2] but also the world's heaviest viperid,^[3] and it has the longest fangs (up to 2 inches), and the highest venom yield of any venomous snake.
• The color pattern consists of a series of pale, subrectangular blotches running down the center of the back, interspaced with dark, yellow-edged hourglass markings. The flanks have a series of fawn or brown rhomboidal shapes, with light vertical central bars. The belly is pale with irregular brown or black blotches. The head is white or cream with a fine, dark central line, black spots on the rear corners, and a dark blue-black triangle behind and below each eye.^[5] The iris color is cream, yellow-white, orange^[5] or silvery.
• Primarily nocturnal, Gaboon vipers have a reputation for being slow-moving and placid. They usually hunt by ambush, often spending long periods motionless, waiting for suitable prey to happen by.
• They are usually very tolerant snakes, even when handled, and rarely bite or hiss, unlike most vipers. However, bites by bad-tempered individuals do occur.
• There have been numerous descriptions of their generally unaggressive nature. Sweeney (1961) wrote they are so docile that they "can be handled as freely as any non-venomous species", although this is absolutely not recommended.
• Parry (1975) described how this species has a wider range of eye movement than other snakes. Along a horizontal plane, eye movement can be maintained even if the head is rotated up or down to an angle of up to 45°. If the head is rotated 360°, one eye will tilt up and the other down, depending on the direction of rotation. Also, if one eye looks forward, the other looks back, as if both are connected to a fixed position on an axis between them. In general, the eyes often flick back and forth in a rapid and jerky manner. When asleep, there is no eye movement and the pupils are strongly contracted. The pupils dilate suddenly and eye movement resumes when the animal wakes up.
• When prey happens by, they strike with very fast precision from any angle. Once they strike their prey, they hang on to it with their large fangs rather than letting it go and waiting for it to die.
• Bites are relatively rare, due to their docile nature and because their range is mainly limited to rainforest areas.^[2] Due to their sluggishness and unwillingness to move even when approached, people are often bitten after they accidentally step on them, but even then in some cases they may not bite.^[13] However, when a bite does occur, it should always be considered a serious medical emergency.
• The snake's hemotoxic venom itself is not considered particularly toxic based on tests conducted in mice. In mice, the LD₅₀ is 0.8–5.0 mg/kg IV, 2.0 mg/kg IP and 5.0–6.0 mg/kg SC.^[14] However, the venom glands are enormous and each bite produces the largest quantities of venom of any venomous snake. Yield is probably related to body weight, as opposed to milking interval.

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• The toes of the gecko have a special adaptation that allows them to adhere to most surfaces without the use of liquids or surface tension. The spatulae tipped setae on gecko footpads facilitate attractive forces called van der Waals forces to arise between the β-keratin lamellae/setae/spatulae structures and the surface.^[9]
• Geckos' toes seem to be "double jointed", but this is a misnomer. Their toes actually bend in the opposite direction from human fingers and toes. This allows them to overcome the van der Waals force by peeling their toes off surfaces from the tips inward. In essence, this peeling action alters the angle of incidence between millions of individual setae and the surface, reducing the Van der Waals force. Geckos' toes operate well below their full attractive capabilities most of the time. This is because there is a great margin for error depending upon the roughness of the surface, and therefore the number of setae in contact with that surface.
• The toes of the gecko have a special adaptation that allows them to adhere to most surfaces without the use of liquids or surface tension. A recent discovery shows that geckos have a special secretial gland that allows them to absorb and excrete liquid to allow for maximum adherence to surfaces. The spatula-shaped setae arranged in lamellae on gecko footpads enable attractive van der Waals forces between the β-keratin lamellae/setae/spatulae structures and the surface.^[12][13]
• Use of small van der Waals attraction force requires very large surface areas: every square millimeter of a gecko's footpad contains about 14,000 hair-like setae. Each seta has a diameter of 5 micrometers. Human hair varies from 18 to 180 micrometers, so a human hair could hold between 3 and 36 setae. Each seta is in turn tipped with between 100 and 1,000 spatulae.^[14] Each spatula is 0.2 micrometer long^[14] (one five-millionth of a meter), or just below the wavelength of visible light.^[17]
• About 60% of gecko species have adhesive toe pads which have been gained and lost repeatedly over the course of gecko evolution ^[21]. Adhesive toepads evolved independently in about 11 different gecko lineages and were lost in at least nine lineages.
• Use of small van der Waals attraction force requires very large surface areas: every square millimeter of a gecko's footpad contains about 14,000 hair-like setae. Each seta has a diameter of 5 micrometers. Human hair varies from 18 to 180 micrometers, so a human hair could hold between 3 and 36 setae. Each seta is in turn tipped with between 100 and 1,000 spatulae.^[18] Each spatula is 0.2 micrometer long^[18] (one five-millionth of a meter), or just below the wavelength of visible light.^[21]
• About 60% of gecko species have adhesive toe pads; such pads have been gained and lost repeatedly over the course of gecko evolution.^[28] Adhesive toepads evolved independently in about 11 different gecko lineages and were lost in at least nine lineages.^[28]

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