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Lucy Hamilton
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1 Instructor s Manual to accompany Animal Behavior, Ninth Edition John Alcock Discussion Questions Chapter 4: The Control of Behavior: Neural Mechanisms 4.1 Suggest how a modern behavioral biologist might explore the effect of a releaser, such as a red dot on a moving gull bill, in terms of changes in gene expression and neural activity in selected portions of the brain of the gull chick. It might be helpful to review the relationships between bird song, neural networks, and the ZENK gene as presented in Chapter 2. Answer: A modern behavioral biologist would probably begin by examining the structure of the gull chick s brain carefully, looking for components likely to be important in visual perception. If such elements could be identified, then he or she might use the techniques that permit the measurement of gene activity in various nuclei via detection of the products of known genes in these neuronal networks. The expectation would be that there would be changes in gene expression in certain brain components immediately following presentation of key visual stimuli, such as a red dot on a moving gull bill, to the gull chick. 4.2 Males of various beetles have been seen trying to copulate with everything from beer bottles to large yellow signs (Figure 4.8). Apply ethological terminology (see Figure 4.5) to these cases by identifying the releaser, the fixed action pattern, and the innate releasing mechanism. Then develop an ultimate hypothesis to account for what clearly is maladaptive behavior on the part of these obtuse beetles (which sometimes die rather than leave the inanimate and unresponsive copulatory partners that they have chosen). Answer: The beetles are responding to the color orange, a releaser of courtship behavior (the fixed action pattern) because these males have an innate releasing mechanism in their brains that detects a particular stimulus and orders a particular response to it. An evolutionary explanation for behavior of this sort is that it was adaptive for males in the past to possess the capacity to respond to the orange color of their mates. In the past, the beetles did not operate in an environment altered by men who throw beer bottles to the roadside and install orange telecommunication signs in beetle habitat. Under the conditions in which the behavior and its underlying proximate mechanisms were evolving, males that were quick to respond to the releaser and highly motivated to court the object associated with it were males that copulated with females and produced male offspring that behaved like they did.

2 4.3 Figure 4.16A shows the location of the tympanic membrane of a noctuid moth. Figure 4.16B shows how the tympanum vibrates in response to sounds ranging from 20 to 80 khz when these sounds are at low intensity (the green curve) and at high intensity (the orange curve). What is surprising about these results? Could these properties promote the moth s ability to detect and respond adaptively to calling bats in its environment? Two points to consider: (1) moths do best at hearing relatively low-frequency ultrasound, and (2) bats shift into high-frequency ultrasound during the last phase of their attack as they attempt to capture flying prey Answer: It is surprising that the tympanum can be designed to vibrate differentially in response to sounds of different frequency and intensity. In particular, low-frequency, low-intensity sounds cause greater tympanal activity than other kinds of sounds. As a result, the moth s tympanum is more likely to stimulate the attached mechanoreceptors when a bat is hunting at some distance from the prey. This should enable the moth to detect a distant predator, which would give the insect time to take effective evasive action against its enemy before it was detected. But if a bat happened to detect a noctuid and was closing in for the kill, the high-intensity, high-frequency ultrasound they produce at this time activates a different pattern of tympanal activity and associated neural signals. This could be the basis for a last-ditch anti-capture response on the part of a moth on a collision course with a bat. 4.4 An American cockroach can begin to turn away from approaching danger, such as a hungry toad lunging toward it or a flyswatter wielded by a cockroach-loathing human, in as little as a hundredth of a second after the air pushed in front of the toad s head or the descending flyswatter reaches the roach s body. A cockroach has wind sensors that react to even slight air movements; these sensors are concentrated on its cerci, two thin projecting appendages at the end of its abdomen. One cercus points slightly to the right, the other to the left. Use what you know about moth orientation to bat cries to suggest how this simple system might provide the information the roach needs to turns away from the toad, rather than toward it. How might you test your hypothesis experimentally? Answer: Hypothesis: The right cercus and left cercus monitor the right rear and the left rear tactile environments for the insect, providing information about the location of potential danger. Prediction: If the right cercus is more strongly stimulated tactilely than the left, this would activate systems that would cause the roach to turn to the left, and vice versa. Test: If one were to surgically remove or otherwise inactivate the right cercus, then a puff of air directed at the right side of the roach would cause the insect to turn to the right rather than toward the left as would be predicted for animals with intact cerci.

3 4.5 Outline Mike May s research in terms of the question that provoked his study and his hypothesis, prediction(s), evidence, and scientific conclusion. In addition, what contribution to this research could come from learning that locusts, a group of insects not closely related to crickets, also possess a special mechanism for very rapidly altering leg positions and wingbeat patterns in reaction to ultrasound, such that a flying individual banks sharply downward away from the side stimulated by the stimulus? 370 Answer: Causal question: What causes crickets to veer away from a source of ultrasound? Hypothesis: Crickets use a hindleg as a brake to slow wingbeat frequency on the side of the body away from the source of ultrasound. Prediction: If one were to tether a cricket and induce wingbeating, then each time the cricket was subjected to an experimental pulse of ultrasound provided by the observer, the away leg would be lifted into the wing, interfering with its activity. Test: The experiment was done with positive results, thanks to high-speed photography. Conclusion: The leg brake hypothesis is probably correct. 4.6 Females of another parasitoid fly related to Ormia track down singing male katydids (Poecilimon veluchianus), whose ultrasonic mate-attracting calls fall largely in the 20 to 30 khz range What sound frequencies should elicit maximal response in the ears of this katydid-hunting parasitoid if stimulus filtering enables the animal to achieve goals that are biologically relevant? What conclusion can you reach based on the data in Figure 4.25? Answer: The parasitoid is predicted to have its hearing tuned to khz. This expectation is matched by the actual data in Figure 4.25, which supports the hypothesis that each animal species employs stimulus filtering to better detect biologically relevant stimuli in its environment. 4.7 Cortical magnification occurs in all mammals. The two cartoonish drawings in Figure 4.30 are cortical maps based on the amount of brain tissue devoted to the sensory analysis of tactile inputs from different parts of the bodies of human beings and of the naked mole rat (see Figure 13.41), a strange, nearly hairless mammal that uses its large front teeth to dig a vast network of underground tunnels while also excavating and processing tuberous roots for food. In what ways do these two maps support the argument that animal brains exhibit adaptive sensory biases? For an additional comparison of the cortical maps of laboratory rats and the naked mole rat see Catania and Henry. 249

4 Answer: Humans and naked mole rats are two very different mammals in terms of their ecological demands, and their brains have evolved accordingly. The emphasis that the naked mole rat s brain puts on analyzing sensory inputs from the teeth reflects the importance of tooth tactile sensations for an animal that relies so heavily on its teeth to dig through immense quantities of dirt and to locate large quantities of plant root food. Human brains devote much more space to the analysis of the tactile signals from the hands (which manipulate tools and grasp a whole range of items) and lips (which are important in feeding and speaking). 4.8 The blue tit is another songbird with a blue patch of feathers that reflect ultraviolet radiation, which is visible to this species. Some ornithologists have reported that female blue tits prefer to pair with males that have relatively bright UV-reflecting feathers on their crowns, 696 while others have found that females mated with such males supply the eggs fertilized by their attractive mates with more carotenoids, a potentially valuable pigment that may enhance the development of their offspring In light of these results, you should be surprised to learn that another team of avian ecologists found that in one population, male blue tits whose crowns reflected less UV produced more offspring than males with more UVornamented crowns. This team suggested that perhaps the males with low-uv crowns were better able to sneak onto neighboring territories and sire extra-pair offspring with their neighbors mates than were males with high-uv crowns (see page 338). How would you test this hypothesis experimentally? List your predictions and then check the results presented in Delhey et al. 381 Answer: The key experimental procedure would be to alter the UV-reflectance of the crowns of a number of male blue tits with the prediction that males whose crowns had reduced UV reflectance would enjoy higher genetic success than other birds whose crown feathers had been manipulated but in ways that did not alter their UV-reflectance or whose crown feathers had actually been altered to reflect more UV. When the researchers who did this work examined their results, they found that males with less UV-reflectance did not have higher reproductive success than those with UV-enhanced crowns. This finding indicates that differences in UV reflectance were not the causal basis for the differences between the two groups of males they observed in nature. 4.9 The ocean-dwelling crab Bythograea thermydron goes through three life stages, which live at three different depths and habitats. The minute larvae float in waters about 1000 meters below the surface, where only a faint blue light penetrates. The older, larger juvenile forms sink into deeper, darker waters, where the only sources of light are luminous fish and other deep-sea creatures that produce their own bluegreen light. Finally, the adults sink to the ocean floor, where they live in the vicinity of deep-sea hydrothermal vents 2500 meters or thereabouts below the surface. Here only the faintest flickers of light are given off at the vents themselves. What would an evolutionary biologist predict about the properties of the eyes of the different life

5 stages of this species? You can check your predictions with information in Jinks et al. 727 Answer: Given the very different kinds of visual environments available for the three life stages of the crab, an evolutionary biologist would predict that the neurophysiology of vision would be correspondingly different. In fact, initially the larval crabs have imageforming eyes that are especially sensitive to blue light. They lose this kind of eye when they sink deeper in the ocean, and instead only have retinas that are most sensitive to wavelengths of light associated with luminous fish. Finally they develop photosensitive cells with very high sensitivity to wavelengths of light given off at glowing deep-sea vents, presumably in order to locate a suitable site at which to settle and reproduce Some evolutionary biologists have argued that the human cerebral cortex contains an assortment of regions specialized for the analysis of an assortment of biologically relevant stimuli. Thus, according to this view, our face recognition mechanism evolved because of the reproductive value for individuals of quickly recognizing the identity of others, given the highly social nature of our species. What problem is posed for this argument by the discovery that we also possess a visual word form area located in the left fusiform gyrus (Figure 4.38)? 959 You are using this particular region of your brain at this very moment as you read these words. In addition, what significance do you attach to the finding that when we read, we recognize each letter independently by its simple features? We never come to recognize words as wholes on the basis of their complexly distinctive patterns, even though we could read far more efficiently if we worked with entire word forms rather than moving from one letter to the next Answer: Since people have only been using and reading written language for about five thousand years, it would seem unlikely that selection has had enough time to lead to the evolution of a module specifically designed to interpret words per se. But perhaps we use a previously evolved module that originally served some other function, perhaps related to object recognition, which has now been taken over in some modern environments in ways that enable us to read. The fact that we do not read as efficiently as we could, if our visual system had been designed specifically for this purpose by a bioengineer of some sort, supports the by-product hypothesis for the operation of the visual word form area We put a homing pigeon on an experimental light dark cycle in which the lights come on at noon and go off at midnight at a time of the year when actual sunrise is at roughly 6:00 a.m. and sunset is at 6:00 p.m. After several weeks on this schedule, we release the pigeon at noon on a clear day in unfamiliar territory due north of its home loft. First, in what direction will the pigeon fly? Second, are you surprised to learn that on a completely overcast day, the pigeon would fly directly home? What does this finding suggest about the homing mechanism(s) of this bird? In this light, consider the findings of a research team in New Zealand who released nearly 100 pigeons near the Auckland Junction Magnetic Anomaly, a place where

6 the Earth s magnetic field is distorted by unusual underground geological features. The New Zealanders found that nearly 60 percent of the birds initially flew on a track aligned with or perpendicular to the local geomagnetic field, but when they got past the Anomaly, they changed direction and headed home. 383 Answer: If it is noon, the clock-shifted pigeon acts as if it is dawn, with the sun in the east. It would therefore fly away from the sun since that would take it west back toward its loft if it really was dawn. However, in actuality, it is noon and if we and the pigeon are in the Northern Hemisphere, the sun will be in the south at noon, and so the clock-shifted pigeon should fly away from the sun, to the north, in its attempt to return to its loft. The ability of clock-shifted pigeons to fly directly home on an overcast day tells us that the birds must possess a back-up homing mechanism that enables them to navigate successfully in the absence of information from the sun s position in the sky. Apparently, this mechanism is independent of the bird s biological clock.

Chapter 4 The Control of Behavior

Chapter 4 Opener: Woodhouse s toad Chapter 4 The Control of Behavior Water toad (Bufo stejnegeri) Bull frog (Japanese) 4.1 A complex response to simple stimuli 4.2 A simple rule of thumb governs this beetle