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Animal Behaviour. AP Campbell Chapter 51. Explaining animal behaviours. What stimulus elicits the behaviour, and what physiological mechanisms mediate the response? How does the animal’s experience during growth and development influence the response?

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animal behaviour

Animal Behaviour


Campbell Chapter 51

explaining animal behaviours
Explaining animal behaviours
  • What stimulus elicits the behaviour, and what physiological mechanisms mediate the response?
  • How does the animal’s experience during growth and development influence the response?
  • How does the behaviour aid survival and reproduction?
  • What is the behaviour’s evolutionary history?

proximate causation

ultimate causation


Many behaviours have a geneticbasis.

  • Since they are heritable, selectivepressurescanact on these traits.
  • Adaptive behaviours are maintained in succeeding generations.
concept 51 3
Concept 51.3

Selection for individual survival and reproductive success can explain most behaviours.

1 foraging behaviours
1. Foraging behaviours

Foraging includes any activities an organism undertakes to search for and procure food.

Optimal foraging theory:

Natural selection should favour foraging behaviours that maximize nutritional benefits while minimizing costs.


Case study: Drosophila larva foraging behaviour

  • Two alleles: forR(rover) and forS(sitter)
  • Larvae with rover gene travel significantly longer paths to forage

How are both alleles maintained in natural populations? Why doesn’t the rover allele become fixed in the population?


Selection favours different alleles depending on the conditions.

  • Why might this relationship exist?
    • potential benefits
    • costs
2 mating behaviours
2. Mating behaviours

The propagation of genetically-based behaviours is dependent on maximizing reproductive success.


Types of mating systems

  • Promiscuity: any male and female will mate within the social group
  • Monogamy: two individuals form an exclusive mating relationship
  • Polygamy: one individual mates with many individuals of the opposite sex
    • Polygyny(the usual form of polygamy)
      • One male, many females
    • Polyandry
      • One female, many males

Male monogamy and parental care are an evolutionary mystery.


Males have the potential to produce many offspring by mating with multiple females.

  • Who is monogamous?
    • Over 90% of bird species are monogamous.
    • Only 3% of mammal species are.
    • Up to 15% of primate species are.

Factors promoting male paternal care

  • Needs of the young

The mate-assistance hypothesis:

Males will help rear offspring in environments where male parental care can greatly promote offspring survival.

The male will produce more viable offspring if he stays and helps, than if he mates with more females.


Certainty of paternity

When is paternal certainty high?

  • When egg-laying and mating are paired, as in external fertilization
  • Exclusively male parental care is rare in species with internal fertilization.

In internally-fertilizing species, males will engage in behaviours that tend to increase certainty of paternity.

  • removal of sperm from female prior to copulation
  • production of large quantities of sperm
  • production of copulatory plugs
  • mate guarding (especially when females are scarce)
    • may be another reason for male monogamy

These behaviours make up an aspect of male-male competition termed “spermcompetition”.


The mate-guarding hypothesis:

Males will stay with a single female partner in environments where receptive female mates are scarce.

Multiple matings with the same female will produce more offspring than mating with more than one.

sexual selection and mate choice
Sexual selection and mate choice
  • Intersexualselection:
    • individuals of one sex are choosy about their mates
  • Intrasexual selection:
    • individuals of the same sex actively compete with one another for mates

Polyandrous species

  • Females compete for mates
  • Females are larger and more ornamented

Polygynous species

  • Males compete for mates
  • Males are larger and more ornamented

Polygamous species are often sexually dimorphic: