•What is the difference between proximate and ultimate explanation?
Casual and developmental factors are referred to as proximate because they
explain how a given individual comes to behave in a particular way during its
lifetime. Factors influencing adaptive advantage and evolution are called ultimate
because they explain why and how the individual has evolved the behavior.
•Reproductive behavior in lions.
Three and twelve adult females, one-six males and several cubs.
At age 3, young related males leave their natal pride. They live as nomads; they attempt
to take over pride from old and weak males. A male’s reproductive life is therefore short.
Female lions show synchronous estrus:
Lions breed throughout the year, females tend to come into estrus at about the same time.
One adaptive advantage of estrus synchrony is that different litters in the pride are born at
the same time and cubs born synchronously survive better. There is communal suckling,
with females lactating together; a cub may suckle from another female if the mother is
out hunting. In addition, synchronous
Hypothesis Testing in Behavioral Ecology
What are the three methods of hypothesis testing?
1) Comparison between individuals and species.
3) Comparison among species.
What is the comparative approach?
The comparative study of different species. We ask questions like: Why does species A
live in groups compared with species B that is solitary?
Breeding behavior of gulls
Gulls nest on the ground, with eggs and chicks are vulnerable to predation. The black-
headed gull seems to make adaptations to decrease this predation risk. For example:
1.) Adults take flight when a predator comes and it gives off an alarm and attacks
2.) They also camouflage their nests by refraining from defecation nearby
3.) They also remove empty eggshells, which have white interiors that attract
4.) The chicks are cryptically colored, and hide in vegetation after hatching.
5.) Parents give off food calls so that they can direct parental care to chicks.
Esther Cullen, Tinbergen’s student, showed comparison between breeding traits
of cliff-nesting gull, the kittiwake.
Kittiwake nests are safer from mammalian predators; can’t climb through steep hills,
and avian predators, wind is too much around cliffs to make attacks. So kittiwake
does not have to do any of the things the black-headed gulls have to do. The kids
remain in the nest until they can fly and also become mixed with other chicks (parents
don’t need to recognize young). There is no need for parental food calls because
young were not hidden. So this shows strong support that various suites of behavior
have evolved as adaptations in response to predation differences between two sites.
The gull comparison only had two species but a larger number of species will
obviously improve the power of the analysis. John Crook did the first systematic
study. Small sparrow-like birds from Africa and Asia build cryptic nests in large
defended territories while others cluster their nests together. Some are monogamous,
others are polygamous.
Crook wanted to search correlations between aspects of social organization and the
species ecology. The variables he considered were food, distribution and
abundance, predators and nest sites.
According to him, the birds fall under two categories:
1) Species living in the forest tends to be more insectivorous, solitary feeders, defend
large territories and build cryptic solitary nests. Monogamous. And both birds
2) Species living in savannah eat seeds, feed in flocks and nest colonially. They are
polygamous and there is sexual dimorphism in plumage.
Why is the behavior and morphology of the weaverbirds linked to their
ecology in such a striking way?
Crook invoked predation and food as the main selective pressures that
influenced evolution of social organization.
1) In the forest, insect food is dispersed. So birds feed solitary and defend their
territory. Since the food is hard to find, parents have to feed the young, therefore
both parents stay together as a pair during breeding season and they’re not
brightly colored to avoid predation.