Prelude to the Case

The Australian redback spider engages in a most interesting and extreme behavior: sexual cannibalism. During copulation, a male somersaults and dangles his abdomen in the jaws of a female. The female begins to eat the male’s abdomen while he continues to copulate with her. Typically, the male engages in two rounds of courtship and cannibalism, the second being fatal. This “clicker case” introduces students to the concept of proximate vs. ultimate causes of behavior. They then are asked to consider the causes of sexual cannibalism, first from the female and then from the male perspective. Using clickers, students are asked to make predictions for various hypotheses and to identify proximate vs. ultimate causes of behavior. Finally, the case presents the interesting conclusion that self-sacrifice is in fact adaptive for male redback spiders.

The case study is presented in class via PowerPoint, with multiple-choice questions sprinkled throughout the “lecture.” Students are expected to answer the questions as they arise using their clickers. The use of clickers in combination with case studies is described in greater detail in the article “Clicker” Cases: Introducing Case Study Teaching Into Large Classrooms.

Go to the PowerPoint presentation (~1.7 MB)

Go to the teaching notes

Date Posted: Novemeber 19, 2009.