Chapter 51: Behavioral EcologyOverview: Studying Behavior- The modern scientific discipline of behavioral ecology studies how behavior develops, evolves, and contributes to survival and reproductive success.Concept 51.1: Behavioral ecologists distinguish between proximate and ultimate causes of behavior- Scientific questions that can be posed about any behavior can be divided into two classes: those that focus on the immediate stimulus and mechanism for the behavior and those that explore how the behavior contributes to survival and reproduction.What is behavior?- Behavioral traits are an important part of an animal’s phenotype.- Most of what we call behavior results from an animal’s muscular activity, such as a predator chasing a prey.◦ In some behaviors, muscular activity is less obvious, as in bird song.- Some nonmuscular activities are also behaviors, as when an animal secretes a pheromone to attract a member ofthe opposite sex.- Learning is also a behavioral process.- Put simply, behavior is everything an animal does and how it does it.Proximate and Ultimate Questions- As we observe a behavior we may ask both proximate and ultimate questions- Proximate questions about behavior focus on the environmental stimuli, if any, that that trigger a behavior, as well as the genetic, physiological, and anatomical mechanisms underlying a behavioral act. Proximate questions are referred to as “how?” questions.- Ultimate questions address the evolutionary significance of a behavior and why natural selection favors this behavior. Ultimate questions are referred to as “why?” questions.- Red-crowned cranes breed in spring and early summer. A proximate question about the timing of breeding by this species might ask, “How does day length influence breeding by red-crowned cranes?”◦ A reasonable hypothesis for the proximate cause of this behavior is that breeding is triggered by the effect of increased day length on the crane’s production of and response to particular hormones. An ultimate hypothesis might be that red-crowned cranes reproduce in spring and early summer becausethat is when breeding is most productive.◦ At that time of year, parent birds can find an ample supply of food for rapidly growing offspring, providing an advantage in reproductive success compared to birds that breed in other seasons.- These two levels of causation are related. Proximate mechanisms produce behaviors that evolved because they reflect fitness in some way. For example, increased day length has little adaptive significance for red-crowned cranes, but because it corresponds to seasonal conditions that increase reproductive success, such as the availability of food for feeding young birds, breeding when days are long is a proximate mechanism that has evolved in cranes.Ethology- In the mid-20th century, a number of pioneering behavioral biologists developed the discipline of ethology,the scientific study of how animals behave, particularly in their natural environments.- In 63’, Niko Tinbergen (ethologist) suggested 4 questions that must be answered to understand any behavior.1. What is the mechanistic basis of the behavior, including chemical, anatomical, and physiological mechanisms?2. How does development of the animal, from zygote to mature individual, influence the behavior?3. What is the evolutionary history of the behavior?4. How does the behavior contribute to survival and reproduction (fitness)?- Tinbergen’s list includes both proximate and ultimate questions. The first two, which concern mechanism and development, are proximate questions, while the second two are ultimate, or evolutionary, questions.Fixed Action Patterns1- A fixed action pattern (FAP) is a sequence of unlearned behavioral acts that is essentially unchangeable and, once initiated, is usually carried to completion.- A FAP is triggered by an external sensory stimulus called a sign stimulus. In the red-spined stickleback, the male attacks other males that invade his nesting territory. The stimulus for the attack is the red underside of the intruder. A male stickleback will attack any model that has some red visible on it.- A proximate explanation for this aggressive behavior is that the red belly of the intruding male acts as a sign stimulus that releases aggression in a male stickleback.- An ultimate explanation is that by chasing away other male sticklebacks, a male decreases the chance that eggs laid in his nesting territory will be fertilized by another male.Imprinting- Imprinting is a type of behavior that includes learning and innate components and is generally irreversible. Imprinting is distinguished from other types of learning by having a sensitive period, a limited phase in an animal’s development that is the only time that certain behaviors can be learned.- An example of imprinting is young geese following their mother. In species that provide parental care, parent-offspring bonding is a critical time in the life cycle.◦ During the period of bonding, the young imprint on their parent and learn the basic behavior of the species, while the parent learns to recognize its offspring. Among gulls, the sensitive period for parental bonding on young lasts one or two days.◦ If bonding does not occur, the parent will not initiate care of the infant, leading to certain death of the offspring and decreasing the parent’s reproductive success.- How do young gulls know on whom—or what—to imprint? The tendency to respond is innate in birds. The world provides the imprinting stimulus, and young gulls respond to and identify with the first objectthey encounter that has certain key characteristics.◦ In greylag geese, the key stimulus is movement of the object away from the young.- A proximate explanation for young geese following and imprinting on their mother is that during an early, critical developmental stage, the young geese observe their mother moving away from them and calling.- An ultimate explanation is that, on average, geese that follow and imprint on their mother receive more careand learn necessary skills, and thus have a greater chance of surviving, than those that do not follow.- Early study of imprinting and fixed action patterns helped make the distinction between proximate and ultimate causes of behavior. They also helped to establish a strong tradition of experimental approaches in behavioral ecology.Concept 51.2: Many behaviors have a