Sociobiology

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Sociobiology

• BS 111
• Ecology Biodiversity

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Learning objectives

• describe social behaviour in terms of costs and
  benefits
• discuss the advantages of social behaviour for
  finding food and avoiding predators
• describe the basic sociobiology of mate
  selection, sexual selection, parental investment
  and of mating systems

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Social behaviour

• Interaction between 2 or more animals (usually of
  same species)
• Aggression, courtship, cooperation, deception
• Costs/benefits
• Sociobiology applies evolutionary theory as
  foundation for interpretation of social behaviour

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Competitive social behaviours

• Contest for resources
• Agonistic behaviour e.g. food, mate
• Tests of strength, threatening displays,
  vocalisations, postures
• Ritual, symbolic displays, often no harm done
• E.g. dogs, wolves show teeth, erect ears, tail,
  looser submissive tucks in tail, looks away

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Cont.

• Ground squirrels inflict severe injury, even
  kill battling for sexually receptive females
• Only receptive a few hrs each yr
• Males reprod. fitness depends on ability to
  compete
• natural selection favours tendency to end contest
  as soon as winner est. (so victor not also
  injured)

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Dominance hierarchies

• E.g. hens put in same pen pecking order
  dominance hierarchy
• Alpha hen controls behaviour of others- benefit
  assured access to food
• Wolves packs coop. necessary for killing prey.
  Each pack dom. Hier. Among females.
• Top female controls mating of others. Food scare
  allows less mating for other females (more for
  her young)

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Territories

• Some spp. defend territories only in breeding
  season may form social groups at other times
  e.g. bird pairs defend small breeding territory
  but form large flocks in winter to forage more
  efficiently/protection from preds.

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Courtship

• complex set of behaviors communicates that other
  not a threat that species, gender, physical
  condition are suitable for mating.
• Complex courtship interaction consists of FAPs
  triggered by some action
• Males more into courtship
• Females more discriminate parental investment
• Also genetic can the males counter
  pathogens/parasites etc???

MALE FRIGATE BIRDS INFLATED SCARLET POUCHES TO
ATTRACT FEMALES
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Mating systems

• Varies between species
• Many species promiscuous
• Monogamous one male one female long period
• Polygamous an ind. Of one sex (usually male)
  with several of the other
• Polyandry single female mates with several males
• Needs of young imp. To evolution of mating
  systems
• Physical characteristics?????

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Why are some birds monogamous?

• E.g. newly hatched birds require large,
  continuous food supply and cannot care for
  themselves
• One parent may not be able to provide all
• i.e. in male interest to stay will provide more
  viable offspring by helping a single mate than
  going off to seek more mates
• May explain why birds are monogamous
• But what about Pheasants, quail?

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Others not???

• Some species young feed and care for
  themselvesless need for parents to stay together
• Mammals..lactating food source ..males no role
  unless protecting harem.
• Certainty of paternity???..why parental care by
  malese.g. external fert. By fish often male
  parental care

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Male jawfish holds the eggs it has fertilised in
its mouth keeping them aerated and protected from
egg predators until the young hatch Certainty of
paternity is higher when mating and egg laying
occur together , as in external fertilisation
e.g. aquatic inverts, fishes, amph, if there is
parental care might be male/female
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Social Interactions and communication

• Intentional transmission of info. Between inds.
  (act by a sender produces detectable change in
  behaviour of another)
• Displays, singing produce response
• E.g. playing tape recording of another males
  song in a male birds territory agitation/may
  attack speaker

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Mimicry and murder in the night

• Fireflies (Photinus)
• Females respond to male flashes for courtship by
  flashing (charac.)
• Photurus female fireflies mimic flashes (not for
  courtship but too eat!)
• males contain defensive chemicals that females
  need to repel predators, such as spiders.
• Mimicry and murder provide a lifesaving meal!
• Defensive chemicals called lucibufagins, which
  Photinus fireflies have and Photuris fireflies
  want, are exuded in firefly blood.

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Deceit within species

• E.g. lions..dominant male takes control of group,
  kills young that are born too soon to be his
  offspring
• Without young, females ovulate sooner
• New dominant male fathers offspring

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Methods of communication

• Visual, auditory, chemical (olfactory), tactile,
  electrical signals
• Which mode related to animals basic lifestyle,
  e.g. nocturnal mammals..visual not effective but
  olfactory/auditory work well
• But birds, mostly diurnal use visual, auditory

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European honeybees (Apismellifera carnica)

• Social, hive bees
• Max. foraging efficiency comm. Location of good
  food sources
• Changes as flowers bloom/new patches discovered
• 1940s Karl von Frisch watched as they returned to
  special observation hives

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• Honeybees showed complex communication with
  symbolic language
• A bee returning from the field - centre of
  attention and performs a dance to communicate
  information about the position of a food source
• Food source close (lt50 m) tight circles waggling
  abdomen/regurgitates nectar
• Excited follower bees to leave hive in search

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• Bees forage up to 5 km from hive
• Waggle dance ½ circle swing in 1 direction,
  straight run, ½ circle other direction (
  regurgitates)
• Indicates both distance direction
• Angle of open hive same as hor. Angle of food in
  relation to sun
• Sounds odors????

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Fig. 51-8c
Waggle dance (food distant)
(c)
A
30
C
Beehive
B
30
Location
Location
Location
B
A
C
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Altruism

• Behave in ways that reduce their ind. Fitness and
  increase fitness of recipient of behaviour
• e.g. ants, bees workers sterile labour for
  queen. Sting intruders..results in death
• Selection sometimes favours altruism Still have
  enhanced genetic representation in next
  generation

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Summary

• Social behaviour dominance hierarchies,
  territories
• Courtship
• Social interactions
• Communication
• Deceit
• Altruism

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Recommended Reading

• Campbell Reece, Chapter 51, pp1133-1144