Alice in Wonderland. Settle down. Make-up. Two-in-one. Ring around the rosie. U-turn. Square dance. Day in, day out. A balanced meal. Tripod. Round of applause ...
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Introduction • The Domain of Animal Behavior • Why study animal behavior? • Curiosity, • Applications: e.g. survival, animal husbandry, wildlife management and conservation, invention such as medicinal plant, • Understanding ourselves, etc..
Animal behavior • Ethology, comparative psychology, behavioral ecology, sociobiology • Ethology • branch of biology • originated from Europe • interested in naturally occurring behavior • observational rather than experimental
1973 Nobel price winners: • K. Lorenz - imprinting • N. Tinbergen – stickle-backed, black-headed gull • K. von Frisch - bee behavior and communication
Imprinting • A form of learning • individuals exposed to certain key stimuli, usually during an early stage of behavioral development • form an association with the object and may later show sexual behavior toward similar objects
Sign stimulus - the effective component of an action or object that triggers a fixed action pattern in an animal • Fixed action pattern - an innate, highly stereotyped response that is triggered by a well-defined, simple stimulus; once the pattern is activated, the response is performed entirely • Releaser - a sign stimulus given by one individual as a social signal to another
Honeybee dances • Round dance < 50 m, waggle dance > 50 m • Direction of food = the angle of the straight-run v.s. vertical • # of complete dance circuit per unit of time • # of waggles during the straight-run portion • the frequency with which sound bursts are produced while dancing
Comparative psychology • branch of experimental psychology • originated from N. America • influenced by Darwin and Pavlov • interested in species differences, especially in intelligence and learning
Behavioral ecology--The study of the adaptive value of behavioral attributes of individuals in solving environmental obstacles to reproduction • Sociobiology (by E. O. Wilson)
Causes of behavior (4 questions) • Proximate/mechanistic (how?) – questions address mechanisms and structures within an animal that give rise to behavior • Examples: • What is the causal relationship between an animal’s genes and its behavior?
Is the trait to some extent inherited from the parents? • How has the development of the animal (e.g. formation of neural pathways, organization of muscles, etc.) affected its behavioral abilities? • What stimuli trigger a response, and how are the stimuli received?
Genetic/developmental – address the “construction” of anatomical/physiological systems that produce behavior • How do gene, environmental, and developmental processes interact to produce the “final” gene-neural-muscle systems that produce behavior • How to variation in gene/environment/ development affect behavior
Physiological – address the functioning to sensory-neuron-muscular systems that produce behavior • How stimuli are perceived, integrated with other information • How decision-making system (e.g. brain, ganglia, etc.) sort information and respond • How effectors perceive/respond to information generated by the decision-making system
Ultimate/evolutionary (why?) – questions try to identify and reconstruct the evolutionary history of a behavior • Has the behavior evolve over time? • If so, why did the changes take place? • What was the original step in the historical process that led to the current behavior
What is the purpose or function of the behavior? What immediate consequence does it have for the animal? • Does the behavior help individuals overcome obstacles to survival and reproduction? • Survival values/evolutionary history
Problems of Comparison • Are the variables biologically relevant? • How broad a taxonomic array of species should be included? • What type of analysis to use? • How to remove effects of confounding variables? • Problems of interpretation
Why infanticide? • Testing alternative hypotheses: • Social pathology - non-adaptive • Regulate population size - group selection • Provide food • Decrease competition • Increase opportunities for mating
S. Hrdy (Am. Sci. 65:40-49, 1977) • Infant death rate↑after♂takeover • Ultimate advantages to♂： • terminate♀pregnancy • destroy another♂'s litter • ♀ carries his own litter
Anim. Behav. 34:785-789, 1986 • Hanuman langurs take-over infanticide at mid- to low density (Kanha Tiger Reserve, India) • Troops: single♂or multi-♂s, ♀s and immatures • All♂bands
Rapid♂replacement/infanticides often observed at sites with high density, degraded habitats and few predators • Gradual♂replacement w/o infanticide in habitats ranging from undisturbed forest to farmland • Sexual selection hypothesis or social pathology hypothesis?
Langur density: 46.15/km2 • Troop density: 1.79/km2 • Band density: 0.51/km2 • 14 troops: 13 single AM & 1 w/ 3 AM • C-troop: 1 AM (AM23), 9~13 AF, 3~4 subF, ~12 immature • All M band Q: 13~16 AM, AM24 is the largest M
Phase 1: Q attacked C, infanticide (kill 3/6 infants: 1m, 1f, 1?) only AFs w/ infants were chased • Phase 2: C-troop splited to two, AM23 + 3AF w/ infant; 5~8 AF, 3~6 AF + 4 subF consort w/ Q AM24 mated w/ mother of the 3rd infant killed
Phase 3: AM30 of Q replace AM23, polarization end, AM30 frequent attack 3 AF w/ infant, and copulated frequently w/ mothers of 1st &3rd infants killed • AM30 most likely be the father of infants born next year • Take-over happened between the birth and the mating seasons • Take-over at mid to low density
Am. Nat. 121: 716-728, 1983 • Lion in Tanzania (15 Prides): 1~7 AM + 2~18 AF + offspring • gestation period~110 days, mean litter size~2.3, cubs wean at 5~8 months, AF sexually active after cubs are ~18 months
Cubs mortality↑after AM take-over, normally, 58/98 litters have at least 1 cub > 6 months • After 10 take-over: 7AF w/ cubs 13~20 month, all evicted; 9 pregnant AF and 10AF w/ cubs < 4 month, all cubs died before 6 months except 2 M
Female responses • defending cubs • avoiding new male --> pride splitting, staying w/ own cubs • pseudo-estrus • spontaneous abortion (Bruce effect) • abandonment
Effect of ♂take-over on♀ reproduction: • reduced fertility, conceived after 6~9 estrus cycles by new male • heightened sexual activity, initiate copulation more, and w/ more partners • Why? • penalize male for infanticide • increase paternal uncertainty • increase male competition • increase birth synchrony
Assumptions: • male>female, force on female • male can ID his competitor's v.s. his own offspring • 4 requirements (BioScience 46: 174- 177) • invading♂kill unrelated infants • bereaved♀will come into heat • invading♂will mate w/ that♀ • new♂will sire more offspring than he would have if he had left the young of other male alone
Anim. Behav. 59: 689-694, 2000 • Male infanticide in captive plains zebra, Equus burchelli • Two zoos in Czech Republic, 5 breeding herds of 4 subspecies • 3~8 breeding mares/herd, enclosure 800~1400 m2, food ad lib
Data: • date of birth • date of death • mother and sire identity • date of introduction of a new male • foals injured by new males and needed vet. care and separation is regarded as dead • weaning time: 9 month as the criterion of survival
Abortion – death of foals on the day of emergence Total abort survive Total (8) 161 35 126 Father 116 20 (17.2%) 82.8% New 45 15 (33.3%) 66.7% New/father (3) 83 18 65 Father 46 5 (10.9%) 89.1% New 37 13 (35.1%) 64.9%
Foal mortality Total dead survive Total 173 17 156 Father 130 9 (6.9%) 93.1% New 43 8 (18.6%) 81.4% New/father99 11 88 Father 59 3 (5.8%) 94.2% New 40 8 (20%) 80%
No significant difference in pre- vs. postnatal mortality, or between sexes • The majority of foals that died when a new male joined were very young, those older than 7 months mostly survived • Probability of foal death was the greatest when the new males joined the herd just after conception, and
Probability of foal death↓w/↑time between conception and date of new male introduction • With a few exceptions, the foal’s chancesof survival↑after 1 month of age • Implication in zoo management - Males are introduced only to herds containing non-pregnant mares and foals > 1 month old