Ch. 50 - Behavioral Ecology

Freeman - Biological Science 8th Edition

Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook

Freeman 8th Edition

Ch. 50 - Behavioral Ecology

Problem 13

Chapter 50, Problem 13

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Mass strandings of whales occur on beaches near military exercises where sonar is used, raising concerns about the effects of human-generated underwater sounds on animal behavior. Scientists are collecting behavioral data on several species of whales to find out how sonar affects them.
Using the graph, estimate the number of minutes of foraging per hour before and after the sound exposure. Then predict the effect of sonar on the fitness of blue whales. Explain your reasoning.

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Examine the graph to understand the whale's behavior before and after sound exposure. The graph shows the depth of the whale below the surface over time, with distinct patterns for breathing and foraging.

Identify the periods of foraging by looking at the depth changes. Foraging typically occurs at deeper depths, as indicated by the graph. Before sound exposure, note the regular dips in depth, which represent foraging activity.

Estimate the number of minutes spent foraging per hour before sound exposure. Count the number of minutes the whale spends at deeper depths (foraging) in the first hour of the graph.

Observe the changes in behavior during the sound exposure period. The graph shows a disruption in the regular foraging pattern, with less time spent at deeper depths, indicating reduced foraging activity.

Predict the effect of sonar on the fitness of blue whales. Reduced foraging time can lead to decreased food intake, affecting the whale's energy balance and overall fitness. Explain how prolonged exposure to sonar could impact the whale's ability to maintain its energy needs and reproductive success.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Foraging Behavior

Foraging behavior in whales refers to the activities and strategies they employ to locate and consume food. This behavior is often characterized by diving patterns, where whales dive to specific depths to access prey. Understanding foraging is crucial for assessing how external factors, like sonar, may disrupt these natural feeding patterns, potentially impacting their energy intake and overall health.

Impact of Sound Exposure

Sound exposure, particularly from human activities like military sonar, can significantly affect marine animals, including whales. Such sounds can interfere with communication, navigation, and foraging behaviors. Analyzing the graph, one can observe changes in foraging depth and duration before and after sound exposure, which can indicate stress or behavioral changes in response to the noise.

Fitness and Survival

Fitness in biological terms refers to an organism's ability to survive and reproduce in its environment. For blue whales, fitness can be influenced by their foraging success, which is affected by external stressors like sonar. If sonar disrupts their ability to forage effectively, it could lead to decreased energy reserves, lower reproductive success, and ultimately impact population dynamics.

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Related Practice

Textbook Question

Evolutionary biologist Hopi Hoekstra and colleagues have hypothesized that the burrow-digging behavior of mice (and the resulting shape of their underground burrows) is heritable—innate and not learned. Design an experiment to test this hypothesis.

Textbook Question

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Mass strandings of whales occur on beaches near military exercises where sonar is used, raising concerns about the effects of human-generated underwater sounds on animal behavior. Scientists are collecting behavioral data on several species of whales to find out how sonar affects them.

Whales communicate with one another using sound. What is one benefit and one cost to whales of using sound to communicate underwater?

Textbook Question

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Researchers followed tagged blue whales to observe how they respond to simulated military sonar—using sound levels much lower than those typically used during military exercises. Analyze the sample of data below for one individual blue whale and summarize the behavioral effect of the sound exposure.

Textbook Question

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Predict why the whale foraged at a depth of 100–170 m.

a. The whale learned to forage at this depth from its mother.

b. The whale had an innate instinct to feed at this depth.

c. The whale's food was most plentiful at this depth.

d. The whale could not dive any deeper than this depth.

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Textbook Question

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The researchers also measured the speed and direction of whale swimming in response to the sound exposure. Whales increase their speed and swim away from the direction of sound. Design a study to test the hypothesis that this behavior leads to beach strandings. Note that you will not receive permission to conduct the study if your actions are likely to cause strandings to occur.

Textbook Question

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There are debates about what action the military should take to avoid harming the whales. How could you apply cost–benefit analysis to address this problem?