Biology 1406 Exam #4

Determine nc, the n at which γ converges to 1/3, for the two flocking events. Are they similar?

(n) declined to 1/3 as n increases. Above about six or seven nearest neighbors, γ remains at about 1/3. This means that an individual bird interacts with about six or seven of his nearest neighbors, and after that he either cannot keep track of any more neighbors or there is no need to keep track of that many. This is shown to be true for the two flock events illustrated.

During the time when there was no hunting inside of the park and no wolves, the elk population increased steadily to a maximum of about __________ individuals.

19,000.

When were gray wolves reintroduced into Yellowstone National Park in two separate releases?

1995 and 1996.

What is the highest frequency of distance between sagebrush plants?

5-10 cm (shorter distances are more frequent).

Nagy and his colleagues found that in _____ of pair-wise comparisons between birds in a flock, one bird was consistently the leader and the other followed.

63%.

The researchers were able to match individual birds in the photographs an average of ______ of the time.

88%.

What percentage of P. fuscatus colonies were found to be initiated by a single female, called a foundress?

94.7%.

What is a behavior in a plant?

A rapid morphological or physiological response to some event, such as attack by an herbivore, in contrast to animal behaviors.

What is a reproductive strategy?

A suite of evolved life cycle-related traits that taken together lead to successful existence of a species in the context of that species' environment.

Predict the response of prey populations when populations of predators are eliminated from an ecological system.

After removal of predators such as wolves from an area, prey populations often increase in abundance very quickly, as you may have predicted. This may be short-lived, depending upon other species with which the prey interacts, and of course these may lead to the indirect effects that are investigated in this section.

When you observe a flock of birds moving as one individual, you have seen an extraordinary sight and an emergent property of an ___________ of animals.

Aggregation.

Volatile communication between individuals has been shown for sagebrush and another plant called _______, although there is evidence suggestive of communication in other plants

Alder.

What is cooperation an example of?

An emergent property.

When are non-worker females and males produced in P. fuscatus colonies?

Around the end of July.

When multiple foundresses cooperate to found a nest, they have intense _______ to establish dominance.

Battles.

Describe the actual and expected distribution of trees of different ages and any differences that you notice between the two distributions. What event corresponds to the time at which differences between the two distributions arise?

Before 1919, the actual number of cottonwood trees in each age category was within the expected distribution and this is because seedling maturation occurred normally. New trees were surviving as expected up until about 1919. However, the number of new trees decreased dramatically by 1920 and there were far fewer trees than expected based on normal reproduction and survival of cottonwoods after that decade. The event that corresponds to this is the total extirpation of wolves from Yellowstone National Park.

Are there advantages to a bird that is a leader in a flock? To a follower? Are there disadvantages in any of those positions?

Being a member of a flock might lead to certain advantages. A member of a flock has many peers on the watch for predators; and if a predator happens along, he or she is not alone. Being a leader may have advantages in that a leader can position itself within the flock, may have more access to resources and may also be a dominant individual in a hierarchy with more access to mates. Advantages to a follower are that the follower can rely on others to make decisions, if it is an inexperienced forager it can follow others to food, and it can be protected within the flock. There might also be disadvantages. Subordinate members of the flock may be more vulnerable to predation, may have trouble keeping up with a flock, and do not get to make directional decisions.

What sagebrush plant experienced the least amount of damage when the experiment was performed with the plastic bags?

Branches on the same plant as a clipped branch that was not bagged.

Nagy and his colleagues found that there was a _________ __________—some birds were leaders in most pair-wise comparisons across flights.

Consistent hierarchy.

Why might cooperation be advantageous in plant populations?

Cooperation may be used to ward off natural enemies such as herbivores or plant pathogens. Plants that cooperate may be able to collectively protect themselves better than an individual can on its own. The close proximity of individual sagebrush plants to each other and the large suite of herbivores that feed on sagebrush facilitated the emergence of a property at the population level that evolved to protect individuals. A population-wide defense strategy would make it more difficult for herbivores to survive, grow, and reproduce; and this would provide a benefit to each individual plant.

The reason that ____________ evolved is considered in the context of it being an emergent property of populations; and to consider that, we must also consider the mechanism.

Cooperation.

There is a ________ ___ _______ within these paper wasp colonies.

Division of labor.

There is a strict __________ _________ among foundresses with the queen being dominant in her interactions with others in the colony.

Dominance hierarchy.

Tibbetts found that the pattern of yellow markings was not correlated with __________ _____ in a colony or a ____________ ______.

Dominance rank; foundress' mass.

In Yellowstone National Park, the wolves primarily eat ____, large deer-like herbivores.

Elk.

If they work in synchrony, an aggregation may behave as an individual unit with ___________ ___________ that is not merely a sum of the individual parts.

Emergent properties.

Although an individual elk is much larger than a wolf, an _________ _________ of wolves is their social behavior of hunting in packs, which allows them to work as a coordinated unit to kill animals much larger than themselves.

Emergent property.

This _________ __________ within the population would lead to increased production of chemical defenses that could be effective against herbivores and lead to success of the entire population of plants against a population of herbivores.

Emergent property.

Why do some females move around before settling in at a colony? Is there any advantage to being in a larger colony versus being in one that is relatively small or to being the lone foundress in a colony?

Females may be assessing their chances of joining a colony in which they will be higher in the dominance hierarchy. More foundresses might be advantageous in situations where there is a high probability that foundresses are related, a large proportion do not have well-developed ovaries, or there is high competition for resources. More foundresses in P. fuscatus colonies led to a disadvantage in that the number of offspring per foundress declined dramatically.

What are examples of aggregations working in synchrony?

Fish schools or bird flocks suddenly changing direction.

a flock of birds can contract, expand, bend, or stretch and still maintain its integrity as a _______.

Flock.

What do queens in paper wasp colonies never forage for?

Food, but they collect pulp and water.

The map shows a lack of first nearest neighbors along the direction of motion, both in _______ and _________.

Front; behind.

Within Yellowstone National Park, the _____ _______ was hunted out of existence before the National Park Service was established to protect the natural resources.

Gray wolf.

What are emergent properties at the population level of social insect colonies?

Group living, cooperation, and division of labor.

What was the set up of the first experiment performed on homing pigeons?

Homing pigeons were fitted with GPS devices and were tested in flocks of nine or ten individuals.

What do food webs depict?

How energy flows in an ecological system. Arrows are drawn between prey and predator with the arrow pointed in the direction of energy flow.

Can you observe movements initiated by one bird that are then copied by another bird? Can you observer individuals that appear to be leaders, and do those leaders rank high in the hierarchical network shown? From your analysis of the movies, does it appear that leaders are at the head of the flock?

In the flock videos an individual turns, after which other individuals copy the movement. There are individuals that are clearly initiating directional changes, although close examination and repeated viewing of the videos are required. Individuals that initiate movement do appear higher in the hierarchical networks determined by the researchers. The leaders are not always at the head of the flock, but because birds have excellent vision to their sides and partly behind them, due to the position of their eyes on their heads, subordinate individuals that happen to be ahead of the dominant individual in flight can still respond to movements initiated by the leader.

Colony size _________ with the number of foundresses, because they can all work together to create a larger group.

Increases.

Reliance on too many neighbors may lead to errors in ____________ _______.

Information transfer.

How cooperation works or how individuals within a group actually do cooperate with each other, which harkens back to __________ transfer.

Information.

What do you conclude about the relationship between wolf and elk populations? That is, can you determine the impact of wolves on the Yellowstone National Park elk population?

It appears that wolves have some impact on the elk population. The elk population declines for a while after wolves are reintroduced. Wolves fluctuate in the early 2000s and then appear to decline, but elk are still declining during that time. We can determine that there is some impact, but not knowing other factors that affect elk, we cannot quantify the impact of wolves on elk.

What is a potential cost of being in an aggregation?

Limited access to food.

What is the difference between an aggregation and a colony/population?

Members of the aggregation come and go, and the aggregation can dissolve and reemerge at a later time.

What places became the only refuge for gray wolves in North America after the mid-1920s?

Minnesota, Alaska, and Canada.

What occurred when the altered wasps were placed back in a colony with the normal wasps and were observed every 30 minutes?

More aggressive acts occurred in the first 30 minutes, but then stabilized to the control value.

How do foundresses in paper wasp colonies exert their dominance over one another?

More dominant females will have aggressive behaviors such as leg or antenna biting, are usually larger, and have more developed ovaries.

Describe the spatial structure of the sagebrush population using the frequency distribution of nearest neighbor distances. How does that relate to the distances at which individuals can communicate with each other?

Most sagebrush plants have their nearest neighbor less than 35 cm away, although a very high proportion has nearest neighbors that are less than 15 cm away. A very small proportion of them are more isolated. Sagebrush can only communicate up to 60 cm, and they can communicate more effectively when they are less than 15 cm apart.

When an individual foundress returns, the other foundresses know that she is a colony-member through her ______ and know her rank in the dominance hierarchy by recognizing her individually through her pattern of facial and _______ ___________.

Odor; body markings.

What is the response of foundresses to experimentally altered foundresses? Is the response sustained over time? What is the response of foundresses to control foundresses?

On average, an experimentally altered foundress received significantly more aggression in the first half hour after yellow facial markings were added or obscured than in the first half hour in the control. Aggression toward experimentally altered wasps declined over time; foundresses received much more aggression in the first half hour than in the half hour beginning 90 minutes after their return. The aggression that control wasps received was lower and did not change over the 2 hour observation period. The altered markings of the experimental wasps were learned by their colony-mates within 90 minutes.

What type of female in the paper wasp colonies has the highest foraging rate?

Other foundresses.

Which type of paper wasp has colonies that can have more total foundresses?

P. canadensis.

What are the two types of paper wasps that were studied in the experiment?

P. fuscatus (temperate species) and P. canadensis (tropical species).

Which type of paper wasp has a higher average number of cells/foundress?

P. fuscatus at lower numbers, but declines dramatically.

How do colony size and the number of offspring per capita vary with the number of foundresses? If only the queen wasp lays eggs, what would be the benefit to other female foundresses to join a colony that had already been initiated by a dominant queen?

P. fuscatus has larger colonies and more cells/foundress compared to colonies of P.canadensis that have the same number of foundresses. Ecological interactions, such as competition or predation, could lead to situations where it is advantageous to have more or fewer foundresses. One advantage to joining a colony and foregoing reproduction is if a joining foundress is related to a queen, because she can help rear offspring that share her genes. If the joining foundress has small ovaries, she would probably produce only a few offspring alone, but she could have higher reproduction if she joined an existing nest and if the probability was reasonably high that she is related to the queen.

Which type of paper wasp has a higher average of cells/colony based on the number of foundresses?

P. fuscatus.

_________ ______ (genus Polistes) are social insects.

Paper wasps.

What plant had the least amount of damage in the second experiment with sagebrush?

Plants/branches that were downwind from a clipped branch.

Describe differences in the social structure and life cycles of P. fuscatus and P. canadensis. Given your knowledge of P. fuscatus, why do you suppose there is a seasonal shift in the type of offspring produced from workers to non-workers and males?

Polistes canadensis is active year-round, while P. fuscatus is not active in the winter. Queens overwinter in this species and emerge in the spring to become foundresses. P. canadensis tends to have fewer offspring in each colony but has more foundresses than P. fuscatus. There is a seasonal shift in P. fuscatus because only workers are required to increase the size of the colony during the summer and later in the season reproductive individuals (queens and males) are needed to mate and prepare for the following spring.

What are potential benefits from living in an aggregation?

Protection, more mates to choose from, and the ability to quickly relay information.

Paper wasps create nests using chewed up plant material, called _______, which dries and has a paper-like texture.

Pulp.

How did homing pigeons come about?

Rock pigeons have an innate homing ability, meaning that they will return to their own nest from long distances away. This allowed humans to use artificial selection to breed birds that repeatedly found their way to a pigeon coop over long distances.

What plant was studied in order to study cooperation?

Sagebrush.

How many birds observed were leaders and followers at one point?

Seven out of the ten birds.

Clearly there are physiological differences between queens and subordinates in the size of their ovaries. But the size of ovaries is not visible to other foundresses. What signals might be used to indicate dominance in such situations?

Size of the individual or behaviors such as aggressiveness or submissiveness would be signals that could indicate or communicate the dominance of an individual. The behavior might be conditional in that an individual would be aggressive if confronting asmaller individual or submissive if confronting a larger individual.

Several diameter classes are missing; trees of certain sizes are simply not found. What could explain their absence?

Small trees, up to about 25-30 cm in diameter, are missing. Because trees grow incrementally, that means that younger trees are missing. However, the figure clearly shows that thousands of seedlings are produced each year. Thus, mature trees are reproducing, but none of their offspring are surviving past the seedling stage. A disease or herbivore that kills young trees could be responsible for this.

What are the first offspring produced in paper wasp colonies?

Sterile workers that help rear more offspring.

In 1992, before wolves were released, elk numbers were about the same as in 1998 and 1999 after wolves were reintroduced. Ask a scientific question regarding the biotic or abiotic factors that could account for similar numbers of elk regardless of the wolves?

The abundances of elk and wolves are not completely related to each other; each population is also affected by many other species and abiotic factors. For instance, the presence of a pathogen could have reduced the elk population prior to the reintroduction of wolves. A drop in food resources for elk during 1990-1992 could have brought down the population in 1992.

From the hierarchical network, calculate the average delay time. What is it? Do you consider this time relatively slow or fast? Examine the flight paths of birds A and M and then for all other birds. What do you observe? Do the delay times between bird A and all other birds correspond to your observations?

The average directional correlation delay time for the flight was 0.47 seconds. This is almost half a second, which might seem very short to most people but might actually be pretty slow in the context of a fast-moving flock. This value represents the reaction times of birds as they follow a directional change made by neighbors they are following. The researchers calculated the overall average directional correlation delay time for all flights to be less than 0.4 seconds. When you observe a flock change direction in mid-air, it appears to be instantaneous. Closer examination of a flock, such as the ones shown in the videos reveals that there is a time delay and the turning of a flock occurs in a wave, from a leading edge to the rear echelon.

What is the purpose of the plastic bags in the final experiment that Karban and his colleagues conducted?

The bagging of clipped branches demonstrated that communication does not occur through the vascular system of the same plant or through some non-airborne mechanism between plants. Clipped branches that were also bagged were not different from the control but were different from the clipped and non-bagged branches.

What are the main differences in the two models analyzed by the scientists? Do the results of the simulations support one hypothesis over the other? Do the simulation results correspond and support the empirical results discussed earlier? Explain.

The distance hypothesis is unable to maintain cohesion; as distance between interacting individuals increases, it becomes more difficult to maintain the flock, especially in the face of disturbance. Only a small proportion of flocks remained as one flock after attack by a simulated predator under the distance hypothesis. A much higher proportion of flocks, over 40%, remained whole after attack under the topology hypothesis. This is the most probable and stable outcome in this set of simulations. By interacting with a constant number of other individuals, individuals in a flock maintain cohesion and the flock can change shape and density without falling apart. The mechanism causes this biological property to emerge at the population level.

What is the distance hypothesis for bird flocks?

The distance hypothesis states that it is the distance between two members in a flock that affected whether and how strongly they interacted.

Why might an individual homing pigeon leave a flock and find its own way home alone?

The lone individual in the homing flight that struck out on its own might have left the flock because it couldn't keep up or perhaps it decided it had a better sense than the rest of the flock as to the direction it should fly. Being alone also presents certain disadvantages, including vulnerability to predation and possibly losing out on resources if arrival to feeding grounds is later than the rest of the flock.

Who are almost always the sole egg-layers in paper wasp colonies?

The queen.

What was the experimental design for examining the starling flock?

The researchers used three sets of two high-resolution digital cameras. Each camera in a set was in a different location. Two of them were spaced 25 meters apart to obtain stereo photographs, and the third was 2.5 meters further to the right. The shutter release cables of the cameras were connected to a timer that fired one set of cameras simultaneously at 5 frames per second (fps) and the other 200 milliseconds later, also at 5 fps to achieve a rate of data collection of 10 fps. The storage capacity of the cameras allowed for 40 photographs, or 8 seconds of flocking.

What do the results of the experiment with marking the paper wasps indicate?

The results indicate that the new markings of a wasp caused the aggressive behavior due to unfamiliarity and that the pattern of markings of P. fuscatus is used for recognizing colony mates.

What did the researchers want to find out about cooperation in sagebrush?

The scientists set out to determine whether or not neighbors in a population of sagebrush plants can detect and respond to information sent by other individuals affected by herbivores or when part of an individual plant is experimentally clipped to simulate herbivory; and if so, how far away signals can be detected by others in the population.

What was found about the diameters of the two different cottonwood species?

The smallest diameter classes (0-20) were largely missing.

Analyze the representation of first nearest neighbor orientation. What do you observe? Where are nearest neighbors located relative to focal birds in a flock of starlings? What aspects of the biology of birds might explain your observations?

The structure of individuals in the flock and the orientation of nearest neighbors are strongly directional. First nearest neighbors are almost never directly in front or directly behind a focal bird. The white areas on the map indicate areas where nearest neighbors are most likely to be—above or below and somewhat to the right or left. Even in a fast moving, fast turning flock of birds, individuals are maintaining a position that keeps their nearest neighbor in that particular position. This is likely caused by interactions between neighbors. Vision is a strong possibility as the mechanism. Birds see very well to their sides because of the position of their eyes.

Evaluate the two hypotheses of topology and distance. Which hypothesis is supported by the data?

The topology hypothesis is supported by the data. The number of interacting individuals is constant across flocks of different density, whereas the distance between individuals varies with density. Within a particular distance, the scientists observed that there were ten birds for the densest flock and only one in the sparsest. If birds in flocks interact with six or seven individuals, that particular distance falls outside the interaction range in one case and within it for the other. Further, nc-1/3 is constant across density, and dc is not.

When studying flocks of starlings, what hypothesis was developed?

The topology hypothesis, which said that interactions between two members of a flock are based on how many other members are in between the pair, not how far apart they are.

What is the value of remaining as a cohesive flock when under attack by a predator?

The value is mainly defense and protection. Once the flock breaks apart individuals can be picked off by predators. It might be much more difficult for a predator to prey on individuals if they are part of a flock.

Investigate the large mammals (larger than rabbits) that are currently present in Yellowstone National Park. List the species you discovered.

There are 67 species of mammals including 7 species of native ungulates (bison, deer, antelope, elk) and 2 species of bears, nearly 300 species of birds, 16 species of fish, 4 species of amphibians, and 5 species of reptiles.

What hypotheses about the markings of paper wasps were rejected and why?

There clearly is a function, so you can easily reject the no-function hypothesis. There was no correlation between the pattern of markings and either size or dominance rank, which allow you to reject the hypothesis that the markings signal rank. The colony membership hypothesis can also be rejected because it turns out that wasps use chemical cues to identify colony-mates, and even though altered foundresses looked different, they were not driven from the nest, which is the habit when foundresses are confronted by a non-colony member. Finally, if the function of the markings is to signal relatedness, the level of aggression that a wasp receives should be the same as long as her appearance is altered. This was not the case.

Describe the variation among P. fuscatus foundresses and speculate on the function of such variation. How does the variation relate to emergent properties of group living?

There is a large degree of variation in the facial and abdominal markings of P. fuscatus. There is more variation in the width and length of yellow markings, and some wasps had other markings not shown. The markings do not correlate with rank or size. Tibbetts hypothesized that the markings were used as signals of individual identity. However, Tibbetts identified several alternative functions that had to be ruled out. Markings could have no function, or they could be used as signals of dominance, membership in a colony, or relatedness among foundresses in a colony. Ultimately, these other functions were ruled out. The variation could be an important emergent property that facilitates group living by allowing individuals to recognize individuals that belong to the colony, or alternatively to determine whether an individual is a stranger.

What was found about the expected distribution of cottonwoods over time?

There was much less growth than expected of cottonwoods from around 1920-1999.

What do P. fuscatus females who were born the year prior but did not start their own colony do?

They joined existing colonies and were also called foundresses.

What is common of subordinate foundresses of P. fuscatus?

They sometimes move from one nest to another.

What is the importance of having a site where the wind blows consistently in one direction, and what are the implications to information transfer in a plant population that communicates via an airborne chemical? What data support the hypothesis that communication between plants is through an airborne chemical? Explain the emergent property that is displayed here.

This was important to the study as the question involved determination of airborne chemical communication. The researchers studied the effects of clipping upwind neighbors on downwind neighbors. In such a natural population it would be difficult for downwind individuals to communicate with upwind individuals.

Why did researchers experimentally alter the markings of several paper wasps?

To determine if foundresses treated altered foundresses as if they were outside intruders and attacked them or if they could recognize altered individuals.

What is a common reproductive strategy in plants?

To produce more seeds than the environment could support as mature individuals.

Why did they cover some of the clipped sagebrush branches with plastic bags?

To prove that these plants are communicating through signals sent via the wind.

The ___________ hypothesis predicts that two birds far apart in a low density flock interact as strongly as two birds close together in a dense flock, provided there are the same number of birds between them.

Topology.

Determine the common deciduous trees that grow in Yellowstone National Park.

Trees: seven conifers (lodgepole pine, whitebark pine, Engelmann spruce, subalpine fir, Douglas-fir, Rocky Mountain juniper, limber pine) and some deciduous species, including quaking aspen, cottonwood, and poplar.

Wolves exhibit emergent properties in their social behavior. Do elk or other large herbivorous mammals exhibit any emergent properties that you would consider an antipredator defense strategy?

Very often they do. They form herds for group defense and exhibit behaviors to protect their offspring. They may become more vigilant, scanning their habitat more frequently, or they may alter their habitat use. Behaviors are emergent properties.

When there is a longer distance in between sagebrush plants, what happens with leaf damage?

When the distance between the plants got larger, the damage to clipped and unclipped plants got closer together. When plants are closer together, the unclipped plants have more leaf damage than the clipped plants.

What happens to the pattern you discerned when the tenth nearest neighbor is analyzed?

When the researchers constructed maps for neighbors farther away, especially after about the 7th nearest neighbor, the strong directionality declined to the point where there was no directionality at all as the order of the neighbor increases. This is shown clearly in analysis of the 10th nearest neighbor.

In order to assess the impact of wolves on elk populations, what else would you want to know in addition to the data? For example, what might you want to know about these populations or their behaviors?

Yellowstone National Park is a very large park and early on there were only 20-60 wolves. We would want to know where they were in the park, how many packs were present, where the elk herds were (and how many different herds there were). We would also want to know habitat use, hunting and predator-avoidance strategies, and breeding seasons (as behaviors during mating might differ from behaviors exhibited the rest of the year).

If one bird consistently initiated movement and the other then copied that movement, the average time differential would be different from ______; but if one bird sometimes led and sometimes followed, the average would be very ______ to zero. These are called directional correlation delay time.

Zero; close.

The slope of the relationship between dn and n1/3 is different for the two flocks shown. What would cause dn to vary with the number of neighbors?

dn varies with the number of neighbors because the density of each flock is different. Denser flocks have shorter distances at any nearest neighbor number (n), and the slope of the relationship for that particular flock is lower than the slope for a sparser flock. The purple flock is thus denser than the teal flock.