chapter 40. key concepts 40.1 behavior is controlled by the nervous system but is not necessarily...

Animal Behavior Chapter 40

Chapter 40 Animal Behavior

Key Concepts 40.1 Behavior Is Controlled by the Nervous

System but Is Not Necessarily Deterministic 40.2 Behavior Is Influenced by Development

and Learning 40.3 Behavior Is Integrated with the Rest of

Function 40.4 Moving through Space Presents

Distinctive Challenges 40.5 Social Behavior Is Widespread 40.6 Behavior Helps Structure Ecological

Communities and Processes

Concept 40.1 Behavior Is Controlled by the Nervous System but Is Not Necessarily Deterministic

Of all animal characteristics, adjustments of behavior are often the most visible responses to environmental change. ◦ Example: Many migratory animals are

changing the timing of their migrations in response to climate change.

Behavioral shifts into new habitats may be the best hope for survival if conditions where they currently live become too warm.

Figure 40.1 Migratory Birds Have Returned Earlier to the Netherlands in the Spring as Temperatures Have Risen


An animal’s nervous system activates and coordinates behaviors.

In humans, particular types of behavior depend on the function of particular brain regions; for example, if Broca’s area is damaged, the person will have difficulty speaking and writing.


Other evidence for the neural basis of behavior comes from the study of highly stereotyped animal behaviors, called fixed action patterns:◦ Expressed by animals without prior learning

and often resistant to modification by learning Examples: begging behavior by gull chicks, web

spinning by spiders

Figure 40.2 Expression of a Fixed Action Pattern: Gull chicks pecking cardboard models

Concept 40.1 Behavior Is Controlled by the Nervous System but Is Not Necessarily Deterministic: Behaviors evolve

Behaviors evolve: if certain alleles produce more adaptive behaviors than others, natural selection can favor those alleles.

Many studies establish that genes can exert important effects on behavior.

Drosophila (fruit flies)mutants for the gene per have altered circadian rhythms.

When the flies are kept in constant darkness, episodes of activity followed 19-hour or 29-hour rhythms, depending on the mutation.

Concept 40.1 Behavior Is Controlled by the Nervous System but Is Not Necessarily Deterministic: Mice data

Experiments with wild populations of house mice collected from Florida to Maine.

When the wild mice were reared in the lab in identical conditions, mice from progressively more northern populations tended to build bigger nests.

This points to evolution by natural selection of a genetically controlled, behavioral propensity to build bigger nests in populations from locations where big nests are an advantage.

Figure 40.3 Nest Building by House Mice from Five Locations

Concept 40.1 Behavior Is Controlled by the Nervous System but Is Not Necessarily Deterministic: Allele Selection

Studies using artificial selection show that behavior can evolve rapidly.

In an experiment with mice, individuals that ran the fastest on a running wheel were selected for mating.

Their offspring were selected in the same way for many generations.

After 13 generations, the selected mice on average ran more than twice as far as control mice.

Further studies showed critical changes in the brains of the selected mice, indicating that a difference had evolved in the neural control of running behavior.


Biological determinism: behaviors of animals are hardwired by genetics

Some simple animals exhibit determinism. ◦ Example: Clams are inflexible in many of their

responses to their environment.


Biological determinism was once applied to human behaviors.

At one time, it was believed that mental capacity was correlated with brain size and that the mental capacities of racial groups could be predicted by measuring relative brain sizes.


Although support for the idea of biological determinism waned during WWII and the Holocaust, when people were slaughtered based on the idea of genetic inferiority, there is an increasing trend of support for determinism today.

It is important to remember that articles written for the general public are not always well supported by objective, statistically supported, relevant data for scientific conclusions.


Behavior is dramatically more flexible than any other biological trait. This is true in part because learning modifies behavior.

New research also shows epigenetic effects on behavior, which can have lifelong influences and may be transmitted from one generation to the next.

Concept 40.2 Behavior Is Influenced by Development and Learning

Learning: the ability of an individual animal to modify its behaviors as a consequence of individual experiences

Experiments with mice show that they learn the layout and hiding places of their environment and that this learning helps them escape predation by screech owls.


Behavioral imprinting: early studies of animal behavior by Konrad Lorenz showed that geese hatchlings learned to view him as their “parent” if he associated with them right after hatching.

This type of learning takes place in a narrow window of time early in postnatal life and, after that, is inflexible.


Indigo buntings migrate at night and navigate by the stars.

Experiments showed that they must know where the north star is and that this must be learned during the 1st few weeks of life.

In a planetarium, young birds learned to identify any star that the sky appeared to be rotating around.

Figure 40.5 The Stars in the Northern Hemisphere Seem to Make Circles around the North Star


The males of many bird species use specific songs to attract females.

The songs are not inherited, but must be learned in the 1st month after hatching from the father, who is singing nearby the nest.

Particular brain regions are required for this learning.

If a young male learns the song of a different species it will later sing an incorrect song and attract females of the incorrect species.


An animal’s early experience can have multiple lifelong effects.

Experiments with rats show that individuals whose mothers exhibited high levels of maternal care during the nursing period were less likely to exhibit fear in novel situations when they were adults.

Regulatory genes in stress-response biochemical and hormonal pathways are tagged with epigenetic marks in early life and are maintained throughout life.


Malnutrition and abandonment in early life are also known to affect epigenetic tagging in rats.

Marks from these early experiences persist into adulthood, altering gene expression and behavior throughout life.


Migratory locusts in Africa can cause crop devastation. An individual locust can display two different behavioral phenotypes:• Avoiding other individuals—the population is

spread out and inconspicuous.• Highly gregarious—the population forms a

swarm. Individuals become a swarm if forced into

close contact, that is, if they are forced to feed next to each other because of food shortage.

Concept 40.3 Behavior Is Integrated with the Rest of Function

Pronghorn running illustrates that an animal’s behavior often depends on and is integrated with the animal’s other characteristics.

Pronghorn have the highest speeds known in running animals.

To behave in this way, they must have muscles that use aerobic respiration and systems to deliver O2 to the muscles at high rates, such as large lungs and muscle cells

packed with mitochondria.


Toads and frogs evolved different behaviors that depend on the type of ATP synthesis:◦ Western toads hop away from danger at

relatively slow speeds that can be maintained for many minutes.

◦ Leopard frogs hop away from danger at lightning speed but are fatigued quickly.

Toads have high levels of the enzymes needed for aerobic ATP production, frogs have high levels of enzymes needed for anaerobic ATP production.


Behaviors are often integrated with body size and growth:◦ Male elk are reproductively mature at two years

of age, but rarely mate before they are five because they must also be big enough and experienced enough to dominate other males.

◦ Young spotted hyenas are limited in their ability to compete with adults during group feeding behavior at a kill because their teeth and jaws are not developed enough to crush bones.

Figure 40.7 Young Hyenas Must Mature to Feed on Bone Rapidly

Spotted hyenas of various ages were given a standardized “bone-crunching test.” The amount of bone they could consume in 15 minutes increased dramatically as they aged and their jaws and jaw muscles became stronger. Young animals are limited in their ability to compete with adults during group feeding behavior at a kill.

Concept 40.4 Moving through Space Presents Distinctive Challenges

• Navigation: the act of moving toward a particular destination or along a particular course• Following trails: worker ants that find a food source lay a

pheromone trail to guide other ants to the food. Pheromone: chemical compound or mixture that is

emitted into the outside environment that elicits specific behavioral responses from other members of the species

Orientation: adopting a position, or a path of locomotion, relative to an environmental cue such as the sun

Navigation


Path integration:Cataglyphis ants liveunderground in hot,dry deserts, butworkers forage aboveground during theheat of the day.

They find heat-killed insects before the bodies have dried out, and thus get water as well as food.

The workers can always run straight back to the nest using path integration.

Concept 40.4 Moving through Space Presents Distinctive Challenges: An Insect Odometer

The worker ant monitors the length and compass direction of each segment of its outbound path.

Then it puts together the information on segment lengths and directions to know where it is relative to its nest.

Figure 40.9 An Insect Odometer (Part 2)

Figure 40.9 An Insect Odometer (Part 3)

Concept 40.4 Moving through Space Presents Distinctive Challenges: Orientation

Orientation◦ Homing pigeons can fly back to their home

nests even after having been transported tens of kilometers away.

◦ One mechanism they use is a sun compass: The birds must observe the position of the sun

and also must know the time of day. They adjust their angle of flight relative to the sun, using their circadian clock to know time of day.

If the pigeon’s circadian clock is entrained with artificial light cycles to be 6 hours off, it will fly in a direction 90° from the correct direction.

Figure 40.10 The Sun Compass of a Homing Pigeon Requires That the Pigeon Interpret the Sun’s Position in the Sky Based on Knowledge of Time of Day


Redundancy in orientation mechanisms is also important.

Homing pigeons can also find their way home on cloudy days. They can detect Earth’s magnetic field and orient to it.

Homing pigeons also sometimes use landmarks such as hills to orient, and they may use odors, low-frequency environmental sounds, and learning from other pigeons.


Many insects and birds can determine compass directions by detecting patterns of polarized light in the sky; requires specialized photoreceptors.

The suns rays are reflected by dust, water droplets, and ice crystals in the atmosphere and become polarized, or aligned parallel to one another.


The Cataglyphis ants in the desert use prominent landmarks if they are present but orient equally well without them using polarized light.

They also have a sun compass.


Honey bee workers can communicate the location of a food source in a specialized behavior called the waggle dance.

During a foraging flight, a worker measures distance to the flowers by visually monitoring the rate at which she flies past local landmarks.

To measure direction, she monitors the angle of her flight relative to the compass position of the sun.

Figure 40.11 The Honey Bee Waggle Dance


Some animals make fantastic long-distance migrations.

Bar-tailed godwits migrate between Alaska and New Zealand, flying non-stop across the Pacific Ocean for 6 to 9 days.


Loggerhead sea turtles hatch out on beaches, and the young turtles head for the sea.

Using genetic markers, researches have found that turtles that hatch in Florida migrate across the Atlantic to African waters, then back to Florida.

Ocean currents help them traverse the sea. The turtles use Earth’s magnetic field to help them complete their journey.

Figure 40.12 Young Loggerhead Sea Turtles Orient to Magnetic Fields as They Travel in a Giant Closed Circle across the Atlantic Ocean and Back

Concept 40.5 Social Behavior Is Widespread: Disadvantages

Disadvantages of living in groups:• Groups of animals are more visible than

individuals.• Diseases can spread more easily within a

group.• A group may rapidly deplete food or other

resources in an area.

Concept 40.5 Social Behavior Is Widespread: Advantages

Biologists presume that group living has evolved only if it provides advantages that exceed its disadvantages.

Much research today focuses on testing hypotheses regarding how individuals in a society benefit from living together in a group.

For some groups, there are physiological advantages—penguins that huddle together to reduce thermoregulatory costs.


In some groups, all individuals have equal status. One advantage is increased awareness of

danger.◦ A group of 50 animals has 100 eyes instead of only 2.

A goshawk’s success in capturing a pigeon in a flock decreases as the number of pigeons in the flock increases.

Belding’s ground squirrels live in large colonies in open meadows and use alarm calls to reduce predation risk.

Aerial predators almost never capture a ground squirrel after the alarm whistles have begun.

Figure 40.13 Group Living Provides Protection from Predators


Animals in groups may find preferred environments more easily.

In experiments with golden shiner fish, researchers found that the larger the school, the more successful they were at finding their preferred low-light habitat.

Concept 40.5 Social Behavior Is Widespread In some societies, individuals have

differing status. Vervet monkey groups have multiple

subadult and adult males, along with females and youngsters.

One adult male dominates all other adult and subadult males in the group and has the best chances of mating with the adult females.

Concept 40.5 Social Behavior Is Widespread

Impala antelopes have two subgroups—one is all males that do not get to mate with females.

The other group has one male and many females.

The dominant male has to expend a lot of energy to repel other males and keep females from leaving, which is exhausting; they tend to retain dominance for only a few months.


In the case of dominant males, the benefit to the group may be that becoming dominant is a test of a male’s strength, endurance, and other properties critical for success.

Females that mate with the dominant male thereby ensure that their offspring are genetically well endowed.


In social insects such as honey bees, a single female (the queen) is reproductive and lays eggs.

Occasionally she produces a few male offspring (drones) that produce sperm.

But most of the thousands of other individuals in the colony—all of which are her offspring—are sterile female worker bees.


Eusociality is a social structure in which some members are nonreproductive and assist the reproduction of fertile members of the group, typically their mother.

Altruism: any characteristic of an individual that imposes a cost on that individual but aids another individual◦ Workers in eusocial colonies exemplify

altruism.

Concept 40.6 Behavior Helps Structure Ecological Communities and Processes

In ecological communities, the behaviors of animals often give structure to the use of time and space and to interrelationships among species.◦ Example: Some animals are active only during

daylight hours, and others are active only at night. These behavioral differences determine whether two species encounter each other.


Behaviors can result in reproductive isolation.

Two species of Peromyscus mice will breed in captivity and produce fertile offspring.

But hybrids rarely occur in nature because the two species prefer different types of woodlands, and thus rarely encounter each other.

Behavior is thus a key factor in allowing species to maintain their species distinctions.


Several of Darwin’s finch species on the Galápagos Islands can interbreed, but behavior ordinarily keeps the species distinct.

Males learn their songs from their fathers, and a female typically will mate only with males that sing the correct song for her species.


Many animals within a population restrict their movements to limited areas.

Behavior can structure the space available.

The region occupied by an individual is a territory if the individual actively keeps out other individuals of the same species.

It is called the home range if other individuals are not excluded.

Figure 40.16 Home Ranges of Male White-Footed Mice in a Woodland


Cost–benefit approach: assumes an animal has a limited amount of time and energy, and therefore cannot afford to engage in behaviors that cost more to perform than they bring in benefits

A study of bumblebee foraging showed that the energy costs of flying and keeping the flight muscles warm while sitting on a flower is higher in cold air than warm air.

Figure 40.17 A Bumblebee Landing on a Flower to Collect Nectar


The amount of energy received in nectar from rhododendron flowers was also determined.

In cold air, a bee needed to visit 7 flowers per minute to equal the foraging cost, but was able to visit 20 per minute.

Thus foraging on rhododendron in cold weather has an advantage and the bees will forage in both cold and warm weather.


Wild cherry flowers are much smaller and have less nectar.

The same type of cost–benefit analysis showed that the bee would have to visit 60 wild cherry flowers per minute in cold weather to get enough nectar to equal the foraging cost.

Thus, the bumblebees only forage on cherry flowers in warm weather.

Chapter 40 Opening Question

In what ways might schooling behavior and pairing behavior be advantageous for the individuals involved?

Answer to Opening Question

Schooling behavior can be advantageous in several ways:◦ A school has more sense organs than a single

individual and can detect predators sooner and find resources more rapidly or efficiently.

◦ Pairing behavior could have several advantages—one being that in male–female pairs, each individual is assured of a mate.

chapter 40. key concepts 40.1 behavior is controlled by the nervous system but is not necessarily...

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