9-12 Dolphin Strandings
Section 1: Welcome to the Activity
Why do bottlenose dolphins strand? What can be done to protect bottlenose dolphins from stranding?
The students will learn what it means when an animal strands. They will learn why bottlenose dolphins strand by analyzing stranding reports and they will identify natural and human-induced causes of strandings. They will also learn ways they can help protect bottlenose dolphins.
The learner will be able to:
- Explain what happens when a bottlenose dolphin strands
- Identify causes of bottlenose dolphin strandings
- Determine if strandings are natural or human-induced
- Understand a dolphin stranding report
- Identify ways they can help protect dolphins
Section 2: Standards
* Bold standards are the main standards addressed in this activity
Biology Performance Indicators
- H.B.1A.1 Ask questions to (1) generate hypotheses for scientific investigations, (2) refine models, explanations, or designs, or (3) extend the results of investigations or challenge scientific arguments or claims.
- H.B.1A.4 Analyze and interpret data from informational texts and data collected from investigations using a range of methods (such as tabulation, graphing, or statistical analysis) to (1) reveal patterns and construct meaning, (2) support or refute hypotheses, explanations, claims, or designs, or (3) evaluate the strength of conclusions.
- H.B.1A.6 Construct explanations of phenomena using (1) primary or secondary scientific evidence and models, (2) conclusions from scientific investigations, (3) predictions based on observations and measurements, or (4) data communicated in graphs, tables, or diagrams.
- H.B.1A.7 Construct and analyze scientific arguments to support claims, explanations, or designs using evidence and valid reasoning from observations, data, or informational texts.
- H.B.1A.8 Obtain and evaluate scientific information to (1) answer questions, (2) explain or describe phenomena, (3) develop models, (4) evaluate hypotheses, explanations, claims, or designs or (5) identify and/or fill gaps in knowledge. Communicate using the conventions and expectations of scientific writing or oral presentations by (1) evaluating grade-appropriate primary or secondary scientific literature, or (2) reporting the results of student experimental investigations.
- H.B.6A.2 Use mathematical and computational thinking to support claims that limiting factors affect the number of individuals that an ecosystem can support.
- H.B.6C.1 Construct scientific arguments to support claims that the changes in the biotic and abiotic components of various ecosystems over time affect the ability of an ecosystem to maintain homeostasis.
- H.B.6D.1 Design solutions to reduce the impact of human activity on the biodiversity of an ecosystem.
Next Generation Science Standards (NGSS)
HS-LS2-2, HS-LS2-6, HS-LS2-7, HS-LS4-5
Inquiry (I) – 2.1
Writing (W) – 1.1, 2.1, 3.1
Section 3: Background
- Marine mammals are endothermic (warm blooded) vertebrate animals that give live birth, breath through lungs, have hair and feed young with milk.
- The bottlenose dolphin (Tursiops truncatus) is the most common dolphin species found off the east coast of the US.
- An animal stranding is when the animal swims or floats into shore and becomes stuck in shallow water.
- Many different marine mammal species can strand in South Carolina, but the majority of those that strand are dolphins.
- Dolphins become stranded for many different reasons. Some of the reasons are human-induced, such as boat strikes, and some are natural such as predator attacks.
- When a stranded marine mammal is found, the South Carolina Marine Mammal Network is called to come out to the scene.
- Data is taken at the site of a stranding and put into a dolphin stranding report
- When possible a necropsy is conducted on animals to determine the cause of stranding. These can occur on site or be conducted later in a laboratory setting.
- Marine mammals face many dangers including marine debris, entanglement, chemical pollutants, and human harassment
- All marine mammals are protected by the Marine Mammal Protection Act.
- Dolphins are an integral part of the ocean’s food webs and they need to be protected around the world in order to save their populations.
- The Charleston area bottlenose dolphin populations are perfect examples of a sentinel species showing us toxin levels specific to different areas in Charleston.
Marine mammals can be found in all of the world’s oceans and in all types of water. They are vertebrates (have a backbone) with the following characteristics:
- Breath air
- Give live birth
- Nurse young with milk
- Have hair
What separates marine mammals from other mammals is that they live in or by the ocean.
Marine mammals are endothermic or warm-blooded. This means that their body temperature is kept at a constant temperature and not controlled by its environment. They are air breathers, using a lungs to breathe. Some species of marine mammals have a blow hole/s, an adaptation that allows them to breathe more efficiently at the surface of the water. Marine mammals have internal fertilization, resulting in a baby through live birth that was nourished by a placenta while in the womb. Mother marine mammals will nurse their young and take care of them for up to a few years depending on the species. All marine mammals live in the ocean with a few exceptions, such as the river dolphins. Some species, like the bottlenose dolphin, also have the ability to live in brackish water, where salt and fresh water mix. Some marine mammals like those within the order Carnivora have hair for their entire life, while others like order Cetacea may only have hair as a newborn that quickly falls out.
Marine mammals include animals from three orders: Cetacea, Carnivora, Sirenia. The order Cetacea includes the whales, dolphins and porpoises which includes about 89 living species. Order Carnivora is divided into many suborders, but only two contain marine mammals adding up to 35 species. Those are Pinnipedia or ‘flipper-footed’ that includes seals and sea lions and Fissipedia or ‘paw/pad-footed’ including polar bears and sea otters. The order Sirenia or ‘sea cows’ is comprised of two aquatic, herbivorous families, the Dugongs and Manatees, and there are just 4 living species. In South Carolina, the most common marine mammal is the bottlenose dolphin.
Bottlenose Dolphins (Tursiops truncatus)
Bottlenose dolphins are in the Order Cetacea, Suborder Odontoceti. The bottlenose dolphin is the most common dolphin species found off the east coast of the US. Bottlenose dolphins are found in tropical to temperate waters around the world and are found in the Pacific, Atlantic, and Indian Oceans. Since they have a global habitat and usually live off the coast, this species has been extensively studied.
Bottlenose dolphins use echolocation to locate their prey and use their sharp cone-shaped teeth to feed primarily on fish. They have been known to strand feed in South Carolina, which is a feeding method where they chase fish onto the beach and then carefully come onshore to grab the fish before sliding back into the water. This feeding method can be dangerous because of the possibility of getting stuck on land.
The bottlenose dolphin, specifically the population around Charleston, have been labeled sentinel species as they can raise an early alarm against biomagnified toxins found within the food web. A sentinel species is similar to an indicator species in that both provide warning signs regarding health. The difference between the two terms is that a sentinel species usually gives warning in regards to human health, whereas an indicator species helps researchers evaluate the health of an ecosystem.
Identifying Bottlenose Dolphins
Photo identification is when a high quality photo is taken of an animal and it is cataloged into a database. Photo ID is a noninvasive identification method for cetaceans. It started in the 1970’s and has become an established way of identifying individual cetaceans by either photographing the animal’s dorsal fin or fluke (tail) depending on the species. When photo identifying a dolphin, each dorsal fin has a unique blend of markings, scars, notches, and other characteristics that make easier to identify an individual. The parts of a dorsal fin are the leading edge, trailing edge, upper third, middle third and lower third.
Tagging dolphins with either a freeze brand or a rototag or radio tag is conducted during catch and release health assessments conducted in partnership with the National Oceanic and Atmospheric Administration. Freeze brands involve super cooling the numbers in liquid nitrogen before being applied to the skin for 20 sec. The three digit code is applied to both sides of the dorsal fin. The first digit represents location and then odd numbers are females and even numbers are males. A rototag is a temporary tag applied to the trailing edge of a dolphin’s dorsal fin. The tags are generally shed within a year of tagging, leaving a small notch or hole.
Marine mammals and sea turtles have been known to strand, which means they swim or float into shallow water and become stuck. A stranding can be just one individual, a mom and a calf, or a mass stranding. Mass strandings consist of two or more animals stranding at the same time in the same general area. In some cases, strandings are designated as an Unusual Mortality Event (UME). To be considered a UME, the event must be unexpected (i.e. different location, different time scale, different age or species of marine mammals), involve a significant die-off of a population, and demand immediate response.
There are many different causes of marine mammal strandings. These causes can be both natural and human-induced. Some main natural causes of marine mammals strandings are shark attacks, stingray barb punctures, and biotoxins. Biotoxins are naturally occurring toxins created by dinoflagellates, diatoms, and other marine algae. Commonly found biotoxins include the neurotoxins domoic acid, brevetoxin, and saxitoxin. Brevetoxin, which is caused by the algae found in red tides, can affect the neurologic systems and cause respiratory problems. The following are causes of human-induced marine mammal strandings: boat strikes, fishery entanglements, pollution (trash or chemical toxins), marine debris ingestion, and sound pollution. Marine mammals can be struck by boats and their propellers can severely damage their bodies. Fishery entanglements is another leading cause of strandings. Marine mammals can having fishing gear wrapped around their bodies or get caught in large fishing nets. Pollution such as oil spills or toxins from manufacturing runoff can make marine mammals sick and this causes them to strand. Marine mammals can also become sick from ingesting marine debris. They will eat trash that resembles their prey and this can cause them to starve. Another form of pollution that can cause marine mammal strandings is sound pollution. The ocean is noisy and has a natural soundscape that marine mammals are accustomed to living in. Human or anthropogenic sounds from shipping, seismic surveying, and sonar are increasing in the ocean. These sounds can impact how marine mammals navigate their environment. Scientists have observed changes in swimming and diving behavior leading to decompression sickness. Decompression sickness occurs when an animal experiences a change in pressure to quickly. If a marine mammal comes up from a deep dive too quickly, the nitrogen dissolved in the blood and tissues can form bubbles that migrate to different parts of the body and block blood vessels.
Stranding Events in South Carolina
On average around 50 marine mammals strand every year in South Carolina. Of those 50, 80% are bottlenose dolphins. When a dolphin or other marine mammal is found stranded on the beach, the Marine Mammal Stranding Network will be called in to assess the situation. If you ever find a stranded marine mammal, call South Carolina Department of Natural Resources Wildlife Hotline 1-800-922-5431. When someone from the Marine Mammal Network arrives on the scene. They will fill out a stranding report. This is a data sheet where all of the information about the marine mammal is documented. The important pieces of information to gather are the species of marine mammal, the approximate age, if it is tagged, and the extent of the injuries or conditions. It is also very important to document where the marine mammal stranded and the type of activity that is occurring. For instance, are a large number of people boating or fishing, was there only one animal or multiple animals?
It can be difficult with marine mammals to determine cause of stranding just from an external evaluation. Conducting a necropsy and taking samples on a deceased animal can help the stranding network determine what caused the stranding. During the necropsy samples of the blood, blubber, organs, and skeleton may be collected along with swabs of any injuries, the blow hole, and mouth. These samples are then taken back to a lab where they can be further examined. During the examination they conduct a number of studies to look for any disease in the tissues or cells, any evidence of viral or bacterial infections or parasites, as well as sample for contaminants and toxins. Finally, the researchers will conduct life history and genetic studies on the animal. They will take cross-sections of the teeth to determine age, examine the reproductive system and stomach contents, and use skin samples to obtain DNA for genetic analysis.
In the state of South Carolina, it is illegal to have cetaceans like whales and dolphins in human care. This makes it difficult to rescue and rehabilitate and animal that strands. In most cases, when marine mammals strand on our coast they have already passed away. If it is a live stranding, do not push the animal back into the water. It stranded for a reason, and pushing it back in means it will strand shortly further down the beach. If it is alive and safe for you to do so, you can try to keep it wet and shaded from the sun by placing wet towels on it.
Bottlenose dolphins, just like all living things, have their place in the ocean ecosystem. Without a balance of animal populations through food chains, communities and ecosystems could become unbalanced. People around the world rely on the ocean for food, oxygen, the earth’s climate and medicines.
About 16% of the world’s food comes from the ocean. This might not seem like a large percentage, but it equals about 200 billion pounds each year. It is thought that about 90% of the world’s oxygen is produced by the phytoplankton of the ocean. This is important because all living things need oxygen to breath. The ocean also plays a huge role in the climate of the earth. The ocean collects and mixes carbon dioxide, heat and water which in turn will control the climate patterns around the world. Researchers are always discovering more about the living things in the ocean. New marine discoveries could lead to medical breakthroughs in cures for diseases and medicines. Many efforts are being done to protect marine mammals around the world.
Protecting dolphins and other marine mammals must include the protection of the waterways as well as the ocean. Marine mammals are federally protected by the Marine Mammal Protection Act that was passed in 1972. This act prohibits the take of marine mammals in U.S. Waters, as well as prohibits U.S. citizens from taking marine mammals outside of U.S. waters, or importing marine mammals or marine mammal products. In South Carolina, there is an additional law that prevents the display of wild caught or captive-bred cetaceans.
Another way to help dolphins is to become dolphin SMART. This is a partnership developed by NOAA’s office of National Marine Sanctuaries and National Marine Fisheries Service, the Whale and Dolphin Conservation, and the Dolphin Project. Their goal is to limit dolphin harassment and promote responsible stewardship.
- S: Stay back 50 yards from dolphins
- M: Move away cautiously if dolphins show signs of disturbance
- A: Always put your engine in neutral when dolphins are near
- R: Refrain from feeding, touching, or swimming with wild dolphins
- T: Teach others to be dolphin smart
Section 4: Procedures
2. Start Intro Presentation by showing stranding pictures. Why do they think animals strand? Is it a normal behavior or abnormal behavior?
3. Explain to the students that marine mammals strand because something has happened to them. Briefly review the types of marine mammals we see in South Carolina on the presentation. Emphasize with the students that bottlenose dolphins are the most common marine mammal in South Carolina.
4. Ask them to brainstorm reasons why marine mammals and specifically dolphins might strand. Do you think they strand due to natural causes, human-induced causes, or both? Go through the primary reasons dolphins strand from the presentation.
5. Inform the students that they are going to be analyzing stranding reports to determine why dolphins stranded.
6. Have students get in pairs. Pass out all 6 stranding reports and ask them to analyze each report to determine why the dolphin stranded. At the top of the report, they should put the reason for stranding and if it was human-induced or a natural cause. Inform them to circle “clues” in the stranding report that led them to their final decision. Note: You may want to put the Primary Strandings Causes
7. When the students are finished, go over the correct answers for each stranding case using the answer key. Ask the students to look at the stranded reports for the dolphins that stranded for human-induced reasons. Could these strandings have been prevented? Is there anything they can do to minimize human impacts on dolphins?
At-home Learning: Have students explore marine mammal strandings using this Wakelet: https://wke.lt/w/s/l-N8he
Wakelet contains the marine mammal stranding powerpoint, links to additional resources, and the stranding reports and worksheet for them to complete. Have students send you their completed worksheet after going through the material.
Virtual: Use the following nearpod information to choose how to teach this activity. Activity will cover the major reasons that dolphins strand and allow them to look at stranding reports to determine how the animal stranded. We have recorded narration on this nearpod which you can access by selecting play on each slide, if you are teaching through a live platform you can bypass this and narrate as you see fit.
Teacher led lesson with student interaction – directions
- Create a free nearpod account (https://nearpod.com/)
- Ask Aquarium to send you Dolphin Strandings nearpod link (email email@example.com)
- After you receive Aquarium link, add lesson to your nearpod activities by clicking “Add to My Library”
- Send to students using Live Participation
- You’ll be able to see their answers and interactions
- How can people help reduce the number of dolphin strandings?
- Would you want to work in the field of animal rescue?
- What type of schooling do you think you would need for a career in animal rescue?
Section 5: Assessment
Scoring rubric out of 100 points
Dolphin Stranding Assessment Worksheet Answer Key
Each question is worth 10 points: 10 questions totaling 100 points.
Section 6: Cross-Curricular Extensions
Design some sort of device that would help a dolphin and keep them from possible stranding. It could help them in anyway (reproductive success, pollution removal from the ocean, etc.). Students should research all the dangers dolphins face and then come up with some sort of device that would help them. Students should share their designs with the class and then modify them per suggestions.
Design a device that would help muffle human caused ocean noise. Students should research what causes sound pollution in the ocean and the devise a device to help. Students should share their designs with the class and then modify them per suggestions. Have students test their devices to see if they work.
Have students research laws that protect endangered and threatened animals and report on how the laws have changed over time.
Section 7: Resources
Gubbins, Cara M. The Dolphins of Hilton Head: Their Natural History. University of South Carolina Press, Columbia, SC, 2002.
Jefferson, Thomas A., Marc A. Webber, Robert L. Pitman and Uko Gorter. Marine Mammals of the World: A Comprehensive Guide to Their Identification. Academic Press, Amsterdam, 2015.
Leatherwood, Stephen and Randall R. Reeves. The Bottlenose Dolphin. Academic Press, San Diego, CA, 1990.
Mann, Janet, Richard C. Connor, Peter L. Tyack, and Hal Whitehead. Cetacean Societies: Field Studies of Dolphins and Whales. University of Chicago Press. Chicago, IL, 2000.
Pearce, Agustin G. and Lucia M. Correa. Dolphins: Anatomy, Behavior, and Threats. Nova Science Publishers, Inc., Hauppauge, NY, 2010.
Pryor, Karen and Kenneth S. Norris. Dolphin Societies: Discoveries and Puzzles. University of California Press, Berkeley, CA, 1998.
Reynolds III, John E., Randall S. Wells and Samantha D. Eide. The Bottlenose Dolphin: Biology and Conservation. University Press of Florida, Gainesville, FL, 2000.
Reynolds III, John E. and Sentiel A. Rommel. Biology of Marine mammals. Smithsonian Institution, Washington, D.C., 1999.
Ridgway, Sam H. and Richard Harrison. Handbook of Marine Mammals, Vol. 6, the Second Book of Dolphins and Porpoises. Academic Press. San Diego, CA, 1999.
Samuels, Joshua B. Dolphins: Ecology, Behavior, and Conservation Strategies. Nova Science Publishers, Inc., Hauppauge, NY, 2014.
Teacher and Student Reference Websites
Dolphin Research Center
Information on dolphins.
Information on the common bottlenose dolphin.
South Carolina Marine Mammal Stranding Network
Information on marine mammal strandings in South Carolina
National Oceanographic and Atmospheric Administration
Information on cetaceans and sounds
Information on sentinel species.
Articles on local dolphins in Charleston, SC
Dolphin Research Center
Project Aquatic WILD
Wild Animal Watch: Dolphins Teacher’s Guide
Wildlife Survivors: A Tale of Two Turtles/Dolphins in Danger
National Geographic: Dolphins Even Smarter Than You Thought
Nature: Whales & Dolphins