FILM SESSIONS. Film session I - Behaviour of Communication (September 30)

Transcription

1 FILM SESSIONS Film session I - Behaviour of Communication (September 30) 1. Talking to Strangers (60 min.) 1 This film surveys some of the general communication signals used by animals from diverse taxa, including insects, amphibians and mammals. Particular emphasis is placed on auditory and visual signals transmitted in a variety of habitats. Examples of signals used by animals the contexts of predator-prey interaction, mating, territoriality, foraging and dominance hierarchies are illustrated. Food for thought: Should signals being transmitted between signaller and receiver always be honest (i.e. truthful)? Can deceitful (dishonest) communication be advantageous to the signaller in certain circumstances? Can different communication signals have the same message? Explain. Think about how an animal s ecology might play a role in the evolution of its communication signals. 2. Why Birds Sing (27 min.) Among birds, usually only the male sings. The structure, function, development and geographical variation of bird songs form the subject matter of this film. Song playback techniques and experimental procedures used by ethologists to study song recognition and song functions in birds are beautifully illustrated. Differences in the structure of predator-mobbing calls and other song types, such as the ones used in territorial defence and courtship, are demonstrated with songbirds and the red-winged blackbird. Finally, the phenomenon of duetting in birds is introduced, followed by a consideration of the evolution and maintenance of geographical variations in songs or dialects in the same species. Think about the following: Design a field experiment to test the possible function of bird song in territorial defence and in mate attraction. Are specific components of song structure important in species song recognition? How

2 2 would you test this? Do predator mobbing calls show structural similarities across bird species? If so, what might be functional significances of such similarities? Does the relative importance of song and body displays in territorial advertisement differ in different habitat (e.g. forests vs. fields)? How are song dialects within the same species established initially and maintained? Explain the usefulness of models in the functional study of animal communication. Film Session II- Conflict and cooperation in social groups (October 21) 1. Fighting (60 min) This film surveys the diversity of behavioural tactics used by individual animals to compete for limited resources such as food, mates and space. Animals use various forms of aggression to settle contests over access to a resource. These range from lowintensity aggression (e.g.ritualized threat behaviour) to outright physical combats (fights), which sometime involve weapons that can cause injury. Most conflicts are resolved using threats. A variety of species (insects, invertebrates, fish, amphibians, birds and mammals) illustrate behavioural conflicts and how they are resolved. Explain why behavioural conflicts over a resource are more commonly resolved using ritualized threats than physical combat. What might prevent a potential cheat (individual with low competitive ability) from using behavioural threats to win an encounter against another competitor over a contested resource? Why is body size an important determinant of the outcome of an aggressive contest between two individuals? Individuals of species with potentially injurious weapons (e.g. canine teeth, horns, antlers, stings) rarely use them against conspecifics when contesting over access to a resource. Why don t they use these weapons more often to win fights?

3 3 2. Friends and Rivals (60 min) Individual animals can choose to live solitarily or in groups. This decision is presumably determine mainly by the individual s assessment of the relative fitness benefits and costs of its available options (i.e. solitary vs. social life). This film surveys some of the known benefits and costs of group living in a variety of animal species, and thus provides insights into the evolution of sociality. The film deals with different kinds of social groups (e.g. bird flocks, primate troops, and colonies) and with the behavioural mechanisms maintaining group structure, dominant-subordinate relationhips, and cooperation and altruism among group members. Can you list the known fitness benefits and costs accrued to individuals of living in social groups? What are some of the factors that might promote the evolution of cooperation and altruism among group members? How can cooperation evolve among unrelated and potentially selfish individuals? Why is division of labour (i.e. social caste system) within colonies so prevalent among insects than any other major taxon of animals? Film session III- Mating and parental care behaviours (November 25) 1. Rivals: the Mating Game (15 min) This short film uses a variety of species of insect to illustrate the process of sexual selection; namely, individuals (usually males) competing with one another for access to mating opportunities (= intra-sexual selection or rival competition) and individuals (usually females) actively choosing particular mates among those available on the basis of some trait(s) the latter possess (= inter-sexual selection or mate choice). Insect species shown include the dung fly, damselfly, stag beetle, butterflies, cricket, moth and scorpionfly. Distinguish between sexual selection and natural selection. Think about how elaborate secondary sexual traits or ornaments in males (e.g. bright colours and plumage) could evolve through sexual selection. What kinds of behavioural tactics, other than courtship, can males potentially use to obtain some mating success?

4 Why are females generally more choosy about who they mate with than males? 2. Courtship (60 min). Successful fertilization of eggs in animals depends on several sequential events or processes occurring during the reproductive season. Some of these include the attraction of one sex by the other, the recognition of the appropriate species and sex, the inhibition of inter-sexual aggression, pair bonding, and physiological synchronization leading up to mating. Courtship behaviour is believed to play an important role in each of these processes. This film surveys courtship behaviour in a variety of species that exhibit different types of mating system, such as monogamy and polygamy (within which the intensity of sexual selection varies). Define courtship behaviour. Why do males exhibit courtship behaviour more commonly than females in most species? What characteristics of the male and (or) its defended resources can be potentially used by the female in mate selection? Is courtship behaviour influenced by sexual selection? What are some of the known costs of courtship behaviour? 4 Do humans show courtship behaviour? What are some of the signals men and women give each other during courtship? 3. Growing Up (60 min) Although most species of animals to not exhibit any parental care, parents in many species do care for their offspring in diverse ways. Depending on the species, both parents may care for their offspring (biparental care), or only the female (maternal care) or male (paternal care) alone provides care. In a few species, adults provide communal care of young. This film surveys diverse parental care strategies in the animal kingdom, and illustrates some of the benefits and costs to the parent(s) in caring for offspring, and the benefits accrued by the latter in receiving such care.

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