What Are Bottlenose Dolphins Doing on Land? an Activity Teaching the Scientific Method through the Unique Behavior of Strand Feeding

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The bottlenose dolphin (Tursiops truncatus) is commonly found along coastal and offshore waters, making this species one of the best studied marine mammals in the United States (Wells & Scott, 2002). Bottlenose dolphins find food by using a variety of methods, such as herding fish into a tight group or using marine sponges as tools to dig for fish in sediment (Smolker et al., 1997; Gazda et al., 2005). In South Carolina and Georgia, bottlenose dolphins use a unique foraging behavior called "strand feeding" (Rigley et al., 1981; Petricig, 1995). At low tide, dolphins work together in groups of two to five to herd fish; then the dolphins create and move along a surge wave that strands the fish on mud banks (Rigley et al., 1981; Petricig, 1995; Duffy-Echevarria et al., 2008; S. Bowen-Stevens, pers. obs.). The dolphins consume the fish stranded on the mud banks before sliding back into the water (Rigley et al., 1981; Petricig, 1995). Marine scientists do not know whether there are certain environmental variables that are favorable for strand feeding. The slope of the mud bank, presence/absence of oysters, or docks may affect the ability of dolphins to catch fish.

Teachers often do not have the time or resources to teach the scientific method (Aultman et al., 2010). Therefore, Aultman et al. (2010) provided a step-by-step process for teaching the scientific method while applying it to real data collected by scientists. We expanded on this template and applied the scientific method to a laboratory study that the students helped create. We designed and tested this activity to teach middle school students about the scientific method, predator-prey relationships, and the effect of habitat on foraging as they assess how mudbank types affect strand-feeding success. The students demonstrated scientific-inquiry and critical-thinking skills.

In this activity, students learn how scientists start with a question and develop a hypothesis. They design their study, conduct trials to collect data, and analyze and interpret the data to test their hypothesis. Students will think about how their results apply to the natural environment through discussion questions. We anticipate that students will gain a greater understanding of science and can apply this knowledge to future science-fair projects or test other predator-prey relationships. Classrooms throughout the country can participate because common materials are used. The activity is also suitable for high school students, given the modifications provided at http://dolphinstrandfeedingactivity.yolasite.com/. This project covers aspects of the National Science Education Standards (National Research Council, 1996), Principles and Standards for School Mathematics (National Council of Teachers of Mathematics, 2000), and Ocean Literacy: The Essential Principles of Ocean Sciences K-12 (National Geographic Society, 2006).

* Background

Teachers may present some of the following information about salt marshes, predator-prey relationships, and strand feeding. Students can also search for additional background material on bottlenose dolphins. Salt marshes are exposed to air at low tide and submerged with saltwater during high tide; thus, salt marshes are intertidal habitats. The water stirs up sediments and provides nutrients for algae and plants such as smooth cordgrass (Spartina alterniflora). Smooth cordgrass can tolerate saltwater and is found in the lower marsh area near the creeks and rivers, where it stabilizes the mud bank. At high tide, salt-marsh vegetation is a safe shelter for young fish; however, at low tide the water recedes and fish move into the creeks and rivers. Predators in the salt marsh include birds, large fish, and bottlenose dolphins. Sharks and other large fish will sometimes prey on juvenile fish as well as blue crabs. Hard substrates can serve as a hiding place or refuge for crabs to escape predation. …