7d. behavioural ecology

animal behaviour includes all the ways animals interact with other organisms and physical environment

• change in activity of an organism in response to a stimulus = external/internal cues
• impact fitness of individuals
  • molded by natural selection
  • influence lifetime reproductive success = measure of fitness

Niko Tinbergen

questions + conclusions he made

how it benefits?

how it evolved?

what caused it?

how it developed?

• environmental differences do not alter behaviour
• animals are born with many instincts already adapted to their environments
• also studied modification of behaviour based on spatial structure of environment

Konrad Lorenz

• studied instinctive behaviours
• imprinting
  • type of learned behaviour with a significant innate component, acquired during a limited critical behaviour
• learning = modification of behaviour resulting from specific life experiences

Karl von Frisch

• studied sensory perceptions of the honey bee
  • translated meaning of the waggle dance
• maturation: behavioural improvement because of ongoing neuromuscular development
  • easy to mistake maturation for innate ability

McArthur and Pianka

• optimal foraging theory: natural selection will benefit animals that maximize their energy intake expenditure

Altruism

• altruistic behaviour: decrease individuals (altruist) fitness, but increases fitness of others (recipient)
• behaviours are selfish
• recipient is related to altruist
• altruist is keeping their own genes in the population
• inclusive fitness: effect on fitness of reproduction (direct fitness) and reproduction of those sharing alleles (indirect fitness)
  • helping relatives increases inclusive fitness, weighted by relatedness

Eusociality

• sterile castes: extreme case of altruism
• in eusocial animals, worker females give up reproduction to raise their sisters
  • bees are haplo-diploid
• relatedness
  • daughter to mother: r = 0.5
  • sister to sister: r = 0.75
• females have greater chance of passing on alleles by raising sisters rather than offspring
• eusocial mammals ex. naked mole rats do not have a haplo-diploid system, but are highly inbred = greater relatedness

Sexual Selection

• competition over limiting sex = sexual selection
• one sex acts as limiting resource
  • why females usually?
  • eggs = rare, energetically costly
  • sperm = cheap and easy to make, less energetically costly
• male reproductive success is limited by mate access
  • more mates for males = greater fitness
  • more mates for females does not obviously increase fitness, but there are a few subtle effects
  • ex. more genetic diversity in one clutch
  • ex. territorial defence
• sexual size dimorphism: increases as harem size increases = stronger combat
• intrasexual selection is direct competition between individuals of same sex for mates
  • physical battles (fighting, vocalizations, ritualized displays)
  • significant risk
• intersexual selection occurs when females are choosy in selecting a male
  • exposes males to extra risks
  • not purely aesthetics, but based on health of individual
• parental investment = time and resources expended for raising of offspring
  • generally lower in males

Certainty of Paternity

• can influence amount of male parental care
  • if make is unsure offspring are his, parental investment is likely lower
  • infanticide: intentionally causing death of an infant by member of same species
• higher if fertilization is external
  • 7 percent of same fish show paternal investment when there is internal fertilization
  • 60 percent if fertilization is external
• investing heavily in offspring that are not yours = worst outcome for males
• monogamy is rare, 3% of mammalian species are monogamous
• monogamy = lasting pair bond between one male and some trivial
  • seasonal monogamy is prevalent in birds, rare among mammals
  • cooperation by both parents is needed to raise young successfully
  • instead of seeking other mates, male fitness increases by investing in his young
  • in lactating mammals, males can contribute little to offspring survival = better to invest energy seeking other mates
• polygamy = individual of one sex mating with two or more individuals of the other sex
  • individuals having multiple mates is generally not involved in parental care
• polygyny = one male mates with multiple females
  • common
• polyandry = one female mates with multiple males
  • phalaropes and sandpipers
  • females compete for males
  • female capable of laying multiple clutches
  • male provide parental