Chapter 52

1. Fixed action patterns are genetically determined, adaptive behaviors that are usually activated by specific stimuli normally encountered in nature. Pavlovian conditioned reflexes are physiological processes triggered by learned, non-natural stimuli. Behaviors resulting from operant conditioning are random behaviors without physiological or adaptive significance; they are activated by non-natural stimuli that the animal has learned to associate with receiving a reward when expressing the behavior.

2. A genetically determined behavior might not be expressed in a deprivation experiment if the animal is not in the appropriate developmental stage or physiological condition, and if the necessary stimuli for the behavior are absent.

3. Proximate causes of mating-display behavior include physiological reproductive condition and presence of stimuli from a sexually receptive conspecific. The ultimate cause of mating-display behavior is reproductive success—how many of one’s offspring live and mature to contribute to the next generation.

1. If the expression of vasopressin and oxytocin genes is increased in montane voles, the voles should be more likely to form pair bonds, and both males and females should exhibit increased parental care. If that result is not observed, it could be due to the lack of receptors in the right brain areas of the montane vole.

2. You would conclude that the trait is likely controlled by a single gene with a dominant and a recessive allele.

3. The evolutionary advantages of having a species-specific mating behavior controlled by a gene expression cascade are that: (1) a single signal can induce a complex combination of responses necessary for that behavior, and (2) temporal coordination of all of those components is ensured.

1. If neonatal genetic male and female rats are gonadectomized, they both develop female sexual responses to estrogen as adults, and they are both unresponsive to testosterone stimulation as adults.

2. The songbird will not sing its song until it reaches sexual maturity, and at that time it has to learn to sing the template it formed as a nestling. To learn, it must practice and hear itself sing. Once its song has crystalized, the bird will be able to sing it even if deafened.

3. Variability in a species-specific behavior such as birdsong might be adaptive if it enables an individual to establish identity with a different local population or to create a new song feature that enhances its attractiveness to potential mates. Variability in this same species-specific behavior could be maladaptive if it detracts from individual recognition. For example, in a situation in which an individual is returning to its nesting grounds to mate with a previously established mate or to feed offspring, it is important to be able to establish individual identity.

1. The benefit of the marsh-nesting site is that it reduces the risk of predation. The cost is that there is greater competition for those sites and less food availability. Feeding in upland areas opens up a greater potential food source, and it does not involve the cost of defending a feeding territory. A risk, however, may be exposure to predation and the need to leave the nest unguarded during feeding.

2. The cost of being a dominant male cichlid is the energetic expenditure involved in territory defense and courtship of females. Also, there are opportunity costs in having less time to feed. The benefit is the likelihood of attracting a mate and fertilizing her eggs. The nondominant male does not incur the costs of territory defense and display and benefits from being able to achieve some reproductive success.

3. Female elephant seals have to have access to a beach to give birth and rear their young, and males can guarantee that access by excluding other males from their piece of beach. Thus the major focus of male elephant seal territorial behavior is exerting physical dominance over other males, and natural selection has optimized the males’ ability to do so. Female elephant seals have no choice over who their “beachmaster” is. In contrast, female prairie-chickens do not need the territory of a male to rear their young, so they are able to simply choose the male they find most attractive. Therefore natural selection in prairie-chickens has favored male displays that are directed at females rather than at other males.

4. One source of selective pressure would be minimization of opportunity costs; therefore the amount of calories obtainable per unit of foraging time would be a critical variable. Another selective pressure is the danger of predation; the relative risk of exposure to predators in the open versus protected environment would be another critical variable.

1. A free-running circadian rhythm is one that is not entrained to a regularly occurring signal, such as sunrise and sunset, but is expressing an endogenous periodicity. When a time cue such as a regular light−dark cycle is imposed on a free-running rhythm, that cue will either phase advance or phase delay the circadian clock to bring it into phase with the environmental light−dark cycle.

2. The direction to the sun can be used to tell compass directions if you know the time of day. A time-compensated solar compass uses an endogenous timing mechanism to compensate for the movement of the sun’s position in the sky. Thus, if a honey bee finds food to the south at noon, its waggle dance on the honeycomb in the hive will be straight up, but as time passes into the afternoon, the direction of the waggle dance will have to be more and more to the left of straight-up to indicate that the direction to the food source is south.

3. The most efficient forms of inter-individual communication are tactile communication, which can be highly specific to the individual, and visual communication, which can convey considerable specific information in a very short time to an individual that is focused on the sender. Sound is an efficient form of communication for a broader population because it permeates the whole environment. Olfaction can be good for either individual or for population communication, depending on the volatility of the odorant.

1. Selection will favor an individual helping its parents raise offspring rather than breeding itself when the chances of its own successful breeding are very low. Raising several brothers or sisters contributes more to an individual’s inclusive fitness than not raising one’s own offspring.

2. Because of the haplodiploid mechanism of sex determination in hymenopterans, sisters share 75 percent of their genes, but parents and offspring share only 50 percent. The unit of reproductive success in eusocial insects is the colony formed around a queen. By helping her mother raise sisters, it is likely that a worker will share 75 percent of her genes with a new queen, but if the new queen were one of her offspring, the worker would share only 50 percent of her genes.

3. The main risk of mobbing a potential predator is the possibility of being attacked and injured by the predator. A benefit of mobbing is that the predator is distracted from focusing on specific prey, such as the eggs or nestlings of the mobbers. The mobbing also warns others in the population of the presence of a predator. Of course, the major benefit is that the predator is driven away. Hypotheses about individuals taking part in mobbing would include that they are likely to be related, that they are more likely to participate if they have nestlings, and that monogamous males are more likely to join in mobbing than are promiscuous males.

1. If the song provides information about mate recognition, the female should show a strong preference for her mate’s directed song over the directed song of other males.

2. Standard deviations are 5.9 and 19.3. The P-value is <0.001. Yes, the females clearly demonstrate recognition of and attraction to their mate’s directed song versus the directed song of an unfamiliar male.

   

3. These data suggest that the directed song provides information about individual identity and plays a role in pair bonding of the male and female.

4. Undirected song may be an opportunity for the male to experiment with and practice slight variations in his song, but it may also represent a lower level of motivation to perform.

1. When females have no larvae or old larvae that no longer need parental care, they invest their energy in producing new broods. However, during the short period when larvae are dependent on parental investment (“new larvae”), the female fertility rate is low. Thus females seem to direct their investment of time and energy into the activities most likely to result in reproductive success.

2. Question 3 of Tinbergen applies. It asks about how a behavior influences survival and reproductive success, and therefore, it deals with ultimate causes of behavior. This study looked into the egg-laying behavior of female beetles under different circumstances. The results can be used to support the hypothesis that female beetles shift their energy expenditures to maximize their reproductive success. This is an ultimate cause of behavior since it deals with evolutionary pressures to maximize reproductive success.

3. The data indicate a correlation between increases in juvenile hormone and suppression of egg-laying behavior. The data also indicate a correlation between increases in methyl geranate and suppression of copulation behavior. These correlations suggest that hormone and pheromone changes may be underlying physiological mechanisms that influence the shift in egg-laying behavior and sexual behavior to parental care behavior in burying beetles.

4. Tinbergen’s question about immediate causation 1 applies, and it deals with proximate causes of behavior. The studies were aimed at elucidating the underlying biological mechanisms that produce the observed changes in behaviors. The results can be used to support the hypothesis that expression of different behaviors comes about as the result of changing levels of hormones and pheromones produced by the female. This is a proximate cause of behavior since it deals with an immediate physiological mechanism that determines how an individual is behaving at a particular time.

5. A cost of the parental care behavior is the opportunity lost for mating and egg laying that could be done instead of caring for young larvae. This means that there are times when the beetles do not actively reproduce, and so fewer offspring are produced over time. A benefit is the protection and nurturing of young larvae, which improves the likelihood that they will survive to carry on the next generation.