FURTHER STUDIES OF BEHAVIOUROption E.6

ASSESSMENT STATEMENTS E.6.1 Describe the social organization of honey

bee colonies and one other non-human example.

E.6.2 Outline how natural selection may act at the level of the colony in the case of social organisms.

E.6.3 Discuss the evolution of altruistic behaviour using two non-human examples.

E.6.4 Outline two examples of how foraging behaviour optimizes food intake, including bluegill fish foraging for Daphnia.

E.6.5 Explain how mate selection can lead to exaggerated traits.

E.6.6 State that animals show rhythmical variations in activity.

E.6.7 Outline two examples illustrating the adaptive value of rhythmical behaviour patterns.

SOCIAL ORGANIZATION Two or more animals interacting with

each other Some animals show limited interaction

while others are extremely sociable Examples?

HONEY BEE COLONIES Nest above ground, usually inside a hollow

tree Wax combs with individual compartments

(cells) for storing honey and rearing young Each hive has one queen whose job it is to lay

eggs Workers are also female, but sterile Workers search for nectar and pollen;

make wax and honey; and feed and protect the young

Workers live for about 6 weeks; queen up to 2 years

Male honey bees (drones) develop from unfertilized eggs and mating with queen is only function

OFFSPRING Queen lays eggs in cells Unfertilized eggs = males Fertilized eggs = females

All fed glandular secretions called royal jelly for the first few days

Larvae destined to be workers are then switched to a less nutritious diet of honey and pollen

Those destined to be queens continue to be fed royal jelly

PHEROMONES Secretions produced by queen to control the

hive Inhibit ovarian development in workers Passed by licking pheromone from queen’s

body and then transferring to food which is exchanged

Most colonies: 60,000 in number If colony gets too large, queen leaves with

“swarm” and establishes a new hive leaving a new young queen behind

SOURCE OF FOOD “scout” bees find source of nectar and

do a waggle dance to indicate the direction and distance of the source

Another chemical is released from the mouth area when the colony is in danger and the signal is spread around to the others

ROLES OF BEES IN THE SOCIAL ORGANIZATION OF THE COLONYQueen Fertile female •Lays eggs

•Produces pheromones which calm the colony and cause other females to be sterile

Worker Sterile female •Feeds the larvae•Produces wax and honey•Searches for nectar and pollen•Protects the hive

Drone Fertile male developed from an unfertilized male

•Mates with the queen

Life cycle video

SOCIAL ORGANIZATION IN CHIMPANZEES Most of our knowledge attributed

to Jane Goodall (ethologist) Highest order of chimp society is

the community Made up of 40-60 members Party smaller group within the

community Party may be all male, a family, or a

nursery unit Make up of parties depends on the food

supply

HIERARCHY Males

Highest ranking is 20-26 yrs old Dominance determined by physical fitness

and fighting ability Strong social bonds exist

Important for keeping out intruders, hunting, and sharing food

Females Dominance in females is linked to age May migrate to other communities Responsible for care of young

COMMUNICATION AMONG CHIMPANZEES Facial expressions Vocalizations Chimp Talk

NATURAL SELECTION Acts on entire honey bee colony, not

individuals Genes selected are those that promote

social organization Pheromones How to find nectar Making of wax Taking care of young

ALTRUISM Worker bees are altruistic They help the queen produce offspring

rather than reproduce themselves Kin selection causes the evolution of

altruism Result is a decrease in fitness* of the

altruist and an increase in the fitness of a close relative

*ability to survive and reproduce

Belding’s ground squirrel Live in mountains of

southwest U.S. Preyed upon by

hawks and coyotes When a predator

approaches, one of the ground squirrels gives a high-pitched call which alerts the rest of the population to the nearby danger

Alarm squirrel (usually female) is more likely to be killed

Females live close to their family, while males live afar

Alarm squirrel does not increase its own fitness but it is increasing the fitness of its relatives

If all the female’s close relatives are dead, she does not sound alarm calls

Naked mole rats Rat colonies can be

up to 100 individuals Live in burrows in

East Africa Workers make

nesting chambers and forage for plant roots needed for food which it brings to queen

Larger workers stay near queen and young

Queen suppresses the sexual behavior of the other females by secreting pheromones in her urine

Also suppresses sexual behavior of the males by bullying except when she is in estrus (ovulating)

Main predator is snake Queen will send workers to attack

snake Workers are sacrificed so queen can

live and preserve the genes of the family

FORAGING BEHAVIOR OPTIMIZES FOOD INTAKE

What an animal eats is essential to survival and ability to reproduce

Behavioral ecologists study foraging behaviors and predict how an animal will forage in a certain set of conditions

They base their predictions on cost-benefit analysis of the behavior

Cost – energy used to locate, catch, and eat food

Benefit – calories of energy gained

SMALL MOUTH BASS Forages for either

minnows or crayfish Minnows have

more energy per unit weight

Crayfish are easier to catch

Small mouth bass show no preference

Each may be optimal under different conditions

BLUEGILL SUNFISH Eats Daphnia Bluegill sunfish

usually forage for the larger ones

They will select smaller Daphnia if the larger ones are too far away

Not selective when density of Daphnia is low

Selective for larger if high density

SCIENTIFIC PREDICTION & RESULTS Prediction:

Bluegills would eat large Daphnia 100% of the time

Results: bluegills only ate large Daphnia 57% of the time

Reasons? Young bluegills not

as efficient as the older ones

Lack of ability to see the size?

Lack of skill?

MATE SELECTION LEADS TO EXAGGERATED TRAITS

Females prefer more highly decorated males

Also size and shape of their tales

Largest tail signifies the healthiest bird with the best chance for healthy offspring

Quality of tail measured by number of eyespots that it has

Studies show that the more eyespots a peacock has the higher number of mates it has

Experiments show that offspring of males with larger tails and more eyespots are larger at birth and survive better in the wild

Could peacock tails become a disadvantage?

Animals show rhythmical variations in activity Reproductive

rhythm Once a year coral

release millions of gametes in a synchronized mass spawning ritual

Predators overwhelmed with more food than they can eat

Feeding behavior North American flying squirrel flies at night Gets the most food and the least

competition

Daily rhythms Diurnal and circadian are both used

to describe a 24-hour cycle of behavior Behaviors are controlled internally

(endogenous), but external (exogenous) cues such as light are important in sychronization

Flying squirrel experiment Placed in total darkness, activity

continued on a 24-hour cycle even without light

Biological clocks are internal mechanisms which keep the animal in sync with its environment, but external cues regulate the biological clock so that it fits a changing environment