Understanding Marine Wildlife Stranding and Response

Learn about strandings of marine mammals and sea turtles and how NOAA Fisheries and partners respond to these animals in distress.

What is a marine wildlife stranding?

Stranded marine life can take the following forms:

  • Whales, dolphins, and porpoises (cetaceans) are considered stranded when they are found dead, either on the beach or floating in the water, or alive on the beach and unable to return to the water.
  • Seals and sea lions (pinnipeds) are considered stranded when they are found dead on land or in the water, or are in need of medical attention. Because healthy pinnipeds come on land to rest, expert assessment may be needed to determine if they need help.
  • Stranded sea turtles are defined as any ocean turtle found on land or in the water that is dead, injured, or exhibits any indication of ill health or abnormal behavior.

Live-stranded animals usually need medical attention or professional assistance to return to their natural habitat.

Strandings of individual animals have been recorded along most of the coastline of the United States, with different patterns depending on geographic location and time of year. Strandings of multiple animals (sea turtles or marine mammals, excluding cetacean cow/calf pairs) simultaneously within a defined area often are referred to as “mass strandings” or “mass mortality events.” When elevated stranding rates occur over a longer time period, the Marine Mammal Protection Act sets out a process to evaluate these events and determine whether they should be designated as unusual mortality events, which trigger a specific investigative response. Mortality events involving sea turtles are investigated under a similar process.

By examining stranded marine mammals and sea turtles, NOAA Fisheries and our stranding network partners can better understand causes of mortality and factors that affect marine animal health. Other goals of stranding response efforts are to facilitate humane care out of animal welfare concerns, assist in the recovery of protected species by returning them to the wild whenever possible, and help identify population threats and stressors of marine life, especially stressors that can be prevented or mitigated.

Which species strand?

Strandings have been documented for many sea turtle and marine mammal species. All species of sea turtles found in the United States are known to strand. Most of the species that occur in U.S. waters, including cetaceans (whales, dolphins, and porpoises) and pinnipeds (seals and sea lions), have also been recorded stranding. However, stranding is more common in some species.

The majority of strandings in the United States are pinniped species, specifically California sea lions, northern elephant seals, and harbor seals. Species that have experienced unusual mortality events range from gray whales to sea otters, but these events occur most frequently in bottlenose dolphins, California sea lions, and manatees. Mass strandings have been reported for multiple species of cetaceans, but are most frequently reported in pilot whales, common dolphins, false killer whales, and melon-headed whales (depending upon geographic area).

What is done to help live stranded animals?

NOAA Fisheries and our stranding network partners of trained and authorized professionals work together to respond to stranded marine animals along most of the U.S. coastline. Given the diverse demands of marine animal strandings—from tiny sea turtle hatchlings to large whales, and individual animals to large groups—the necessary actions include a wide breadth of responses. When a live stranded animal is reported, designated network members respond as quickly as possible to assess the condition of the animal. Larger animals and stranding events require a team of responders who consider a number of factors, including human and animal safety, to determine the appropriate course of action. The team may attempt to release the animal immediately back out to the ocean at the stranding site or relocate the animal to a different beach. Some animals need to be disentangled. In some cases, the stranded animals are so sick or injured that the most humane option is euthanasia. Other times, rehabilitation is an appropriate response.

If the animal is determined to need rehabilitation, there are authorized marine mammal and sea turtle rehabilitation facilities in various U.S. locations. These facilities provide specific expertise and specialized facilities for housing, husbandry, and medical care. If an animal is determined to be healthy enough for release, it is returned to its natural habitat. Each year, many animals are rehabilitated and eventually released. During the rehabilitation process, animals are assessed for their ability to be released back into the wild. Although most stranded animals are successfully released, each year a small percentage are determined to be unable to survive in the wild. These “non-releasable” animals are placed in facilities for permanent care. Placement of marine mammals into captivity is regulated by NOAA Fisheries and follows a systematic process that ensures equitable, transparent, and fair consideration for candidate facilities, which are permitted by the USDA under the Animal Welfare Act. Permanent care facilities for sea turtles are permitted by the U.S. Fish and Wildlife Service, which specifies standard requirements for housing and care.

Why do animals strand?

Marine animals strand for numerous reasons, and the predominant known causes vary by species. Some of the common general causes include:

  • Injuries caused by ship/vessel collisions.
  • Entrapment or entanglement in fishing gear.
  • Viral and bacterial infections.
  • Parasitism.
  • Disease resulting from exposure to harmful algal blooms.
  • Other diseases, including cancer.
  • Starvation.
  • Unusual weather or oceanographic events.

Some animals may strand for several of these reasons. In many instances, a specific cause cannot be determined. Nonetheless, each stranding is an opportunity to learn more about marine animals and causes of strandings. NOAA Fisheries works closely with stranding partners to ensure consistent collection of information and samples necessary to investigate strandings and conduct other important health studies. These efforts have led to a number of significant advances in our understanding of strandings and have provided valuable information to help mitigate some human causes.

How often do strandings occur?

Each year, thousands of stranded marine animals are reported to stranding networks. Sporadic strandings of individual animals are relatively common in many areas, depending on geographic location and time of year. Stranding or mortality events involving larger numbers of animals typically are less frequent. One of the most well-known examples is mass stranding of cold-stunned turtles during winter months. These events occur in predictable locations on the Atlantic and Gulf coasts and can involve thousands of sea turtles requiring care.

Who responds to marine animal strandings?

The National Marine Mammal Stranding Network, created under the Marine Mammal Health and Stranding Response Program, was formalized in the 1992 amendments to the Marine Mammal Protection Act. The network consists of more than 100 organizations that partner with NOAA Fisheries to respond to and investigate marine mammal strandings including whales, dolphins, porpoises, seals, and sea lions.

The Sea Turtle Stranding and Salvage Network (STSSN), formally established in 1980, responds to and collects data on strandings of marine turtles along the U.S. Gulf of Mexico and Atlantic coasts. The network encompasses the coastal areas of the 18-state region from Maine to Texas, and includes portions of the U.S. Caribbean. The Marine Turtle Biology and assessment program established in 1990 in the Pacific Islands rescues, rehabilitates, and studies stranded sea turtles throughout the Hawaiian Islands. The program partners with state and local governments, universities, conservation organizations, and private businesses of the Hawaiian Islands to rescue and release sea turtles.

These stranding networks are established in all coastal states and are authorized through NOAA Fisheries (marine mammals) or the U.S. Fish and Wildlife Service and other designated agencies (sea turtles). Network members include professionals and volunteers from nonprofit organizations, aquaria, universities, and state and local governments who are trained in stranding response, animal evaluation, and administration of animal care. Through a national coordinator and regional coordinators, NOAA Fisheries oversees, coordinates, participates in, and authorizes response activities and provides training to stranding network personnel.

Stranding network partners play an important role in responding to marine wildlife in distress. They are the first responders on the beach when a stranded animal is reported, and some organizations are responsible for transporting and rehabilitating sick or injured marine mammals and sea turtles. Together, NOAA Fisheries and stranding network members ensure that animals in trouble are treated humanely. In addition, they collect data to help determine what may have caused a particular animal to strand. Scientists also use the data to help provide context for larger ocean health trends.

What can we learn about marine animals from strandings?

Strandings provide a great deal of information to researchers and resource managers. Information collected provides many insights into the lives of marine animals, including seasonal distribution, natural history, population health, environmental contaminant levels, cases of human interaction, and incidence of disease. For some species, the only existing information was gained from stranded animals. NOAA Fisheries helps facilitate the exchange of information between stranding network members, so that response and treatment activities for stranded animals can be consistently improved.

Samples taken from live stranded animals provide important data that rehabilitators and veterinarians can use to determine the best course of treatment. This type of information helps build a more comprehensive understanding of wild marine animals.

When stranded animals die, experts perform a necropsy—an animal autopsy—to learn more about why the animal died and to inform future responses. A necropsy also can tell researchers what an animal ate, and whether it was or had been pregnant. Through necropsies we have learned a significant amount about the basic physiology and biology of animals that are not accessible in the wild or through other means. For example, the National Marine Mammal Tissue Bank stores marine mammal tissue to support multiple analyses and provide long-term sample stability for future research. These types of sampling opportunities also help validate and increase understanding and interpretation of data collected from wild populations.

What should I do if I find a stranded animal?

If you see a stranded marine animal, do not approach it. And, do your best to keep other people and pets from disturbing it. Then:

  • Call your local stranding network [new report a stranding page in Drupal].
  • Or, use the Dolphin & Whale 911 iPhone/iPad app | Android app

Marine mammals and sea turtles are wild animals and often behave unpredictably. Do not let pets approach marine life. Keep a safe distance when calling in information to the stranding hotline. Remember, if you are not a trained professional or volunteer, you should not handle marine life.

Once you report the stranding, responders will travel to the scene as quickly as possible, where they will assess the situation and appropriately respond to the animal’s needs. Quickly and accurately reporting a marine animal stranding is the best way to ensure professional scientists and responders know about the incident and can respond appropriately. Be sure to provide an accurate description of your location when reporting a stranded animal.

It takes cooperation and effort from everyone involved to respond promptly to marine life in distress. Beachgoers and boaters are often the first to see stranded marine life, and are a key part of making sure professional responders know about a stranding incident and arrive on the scene quickly.

While NOAA Fisheries and our partners have the responsibility of responding to sick and injured marine animals, you can also help prevent injuries from happening in the first place. For example, remember to view marine mammals and sea turtles responsibly and do as much as you can to keep marine debris out of the ocean. These simple actions can protect marine life and help keep these animals thriving.

You can also support efforts to understand and investigate marine mammal Unusual Mortality Events by donating to the Marine Mammal Unusual Mortality Event Contingency Fund. Your contributions will be used exclusively to cover the costs incurred by our stranding network partners during unusual mortality event responses and investigations.