Title: Sociobiology
1Sociobiology
- BS 111
- Ecology Biodiversity
2Learning 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
3Social 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
4Competitive 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
5Cont.
- 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)
6Dominance 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)
7Territories
- 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.
8Courtship
- 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
9Mating 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?????
10Why 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?
11Others 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
12Male 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
13Social 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
14Mimicry 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.
15Deceit 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
16Methods 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
17European 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
18- 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
19- 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????
20Fig. 51-8c
Waggle dance (food distant)
(c)
A
30
C
Beehive
B
30
Location
Location
Location
B
A
C
21Altruism
- 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
22Summary
- Social behaviour dominance hierarchies,
territories - Courtship
- Social interactions
- Communication
- Deceit
- Altruism
23Recommended Reading
- Campbell Reece, Chapter 51, pp1133-1144