Standards Addressed

Background

Virtual Field Trip

Classroom Activities

1. Photo-ID
2. Ecological Role of Bottlenose Dolphins

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Glossary

Teacher Guide

Marine mammals are believed to be very important to the structure and function of marine communities.  As top predators, they take a significant amount of prey from any given system.  In turn, they are affected by changes in the system.  Marine mammologists must look at the entire system  as a whole functioning unit.

North Inlet, an estuary located north of Georgetown, SC, is a National Estuarine Research Reserve.  It is home to research focusing on many aspects of the estuary, including its resident population of bottlenose dolphins, Tursiops truncatus.  These dolphins spend most of their time within the tidal salt marsh creeks of this 32 km² system, though they also use the adjacent waters of Winyah Bay and the Atlantic Ocean.  The dolphin studies provide data for future management decisions concerning dolphins, as well as the fisheries represented by their prey.  The dolphins can serve as an indicator species for seasonal and long-term changes in the estuary.

Much of the research depends first upon the ability to identify and track the dolphins in North Inlet.  To do this, “focal follow surveys” are conducted, in which a specific dolphin or group of dolphins are followed continuously as they go about their daily lives in the estuary.  Dolphins are photographed during each study day and are then identified by the unique shape of their dorsal fins.  Trying to match pictures of fins with a “catalog” of previously identified fins is challenging, and requires researchers to develop an eye for detail.

Photo-identification techniques have become standard practice for cetacean biologists.  Developed in the 1970s, bottlenose dolphins, Tursiops truncatus, and killer whales, Orcinus orca, were the first species of odontocetes to be investigated (Leatherwood and Reeves, 1990).  The natural markings on the dorsal fins, including notches, nicks, and scars, are used for identification.

Building on previous ecological research by many other scientists, Young and Phillips (2002) developed an ecological model  to estimate the impact of the resident dolphin population on the North Inlet food web.  This activity examines this models in detail. 

The activity consists of two modules.  One exposes students to the challenge of dolphin identification using actual photos of North Inlet dolphins.  The other module challenges students to follow in researchers’ footsteps by investigating the dolphins’ role in the food web and calculating the annual primary production required to support them.