How Experts Properly Dispose of Dead Marine Mammals

Have you ever wondered what happens to a marine mammal after it dies? Proper disposal of a carcass—which can be the size of a school bus—can be complex and logistically challenging. Local governments decide how to remove and dispose of dead marine mammals, but they may receive guidance and assistance from partners in the National Marine Mammal Stranding Network, which is coordinated and authorized by NOAA Fisheries. 

Responsibility for Disposal

The local landowner (e.g., town, city, park, homeowner) is responsible for the removal and disposal of a marine mammal carcass. Before handling or attempting to move any deceased marine mammal, they should coordinate with the local Stranding Network. The Network does not respond to every case and is not legally responsible for carcass disposal. However, they can play an important role in identifying disposal sites and communicating with the landowner or land manager about the applicable laws and regulations governing marine mammal carcass disposal.

The Stranding Network can also collect valuable health information from the carcass. This data can provide insight into the stranding event and may be used more broadly to monitor diseases, determine species distribution shifts, and mitigate threats to marine mammal populations. For smaller animals—such as dolphins, porpoises, seals, and sea lions—network responders might choose to take the carcass to their facility for further study. If they do, they are responsible for disposing of the carcass after their examination is finished.

Types of Disposal

The Stranding Network can help the landowner identify appropriate disposal options. The best disposal method for each case can depend on several factors:

• Human safety
• Location, accessibility, and weather
• Species
• Animal size
• Number of carcasses
• Available personnel and resources
• Drug administration (e.g., whether responders gave the animal sedative or euthanasia medications)

Every method has benefits and drawbacks, and no single method suits every stranding situation. Methods for disposing of marine mammal carcasses fall into two main categories: 

• Remain in the environment (natural decomposition)
• Remove from the environment (and further processing by industrial means)

Leaving a carcass to decompose naturally in the environment is the most basic and cost-effective method. Examples include:

• Leaving the carcass above ground where it was found or moving it to a more remote area
• Burying the carcass
• Towing the carcass offshore and releasing it (floating)
• Sinking the carcass offshore 

On-Site Burial

In high-traffic areas, teams may bury a marine mammal carcass where it was found if the resources are available to do so. On-site burial creates a disease barrier and reduces scavenger attraction. Teams must ensure the carcass is buried above the high tide line and groundwater table. This method may require heavy equipment and local permission and is considered on a case-by-case basis. Not all locations are suitable for beach burial (e.g., rocky shoreline or sites with limited accessibility). 

Disposal at Sea

Disposal at sea (either floating or sinking) is an option if: 

• The stranding site is in a public area and there is no place nearby to relocate the carcass
• The carcass is mostly intact (not heavily scavenged or decomposed)

Typically, only large whale carcasses are disposed of at sea. However, in some areas, such as the Pacific Islands, this disposal method is culturally preferred. At-sea disposal requires permits and is expensive given the high costs of specialized towing vessels, logistics, and labor needed to safely move an animal weighing several tons. 

The carcass could be sunk, rather than left to float, if the disposal location is:

• A semi-enclosed body of water or area with strong currents where likelihood of restranding is high
• Near shipping lanes where a floating carcass could pose a hazard to navigation

Sinking a carcass at sea can be logistically complicated, potentially dangerous, and further increases the cost.  

Marine mammal carcasses are a vital part of the ecosystem. They slowly break down over many months or years, returning nutrients to the environment. Natural decomposition provides an important food source for:

• Terrestrial scavengers, insects, and microbes when the carcass is on shore
• Marine scavengers, including sharks
• Entire seafloor communities when the carcass sinks at sea 

A whale carcass that sinks to the sea floor—known as a whale fall—can provide habitat for years or even decades, depending on its size.  

Removal from the Environment

Letting a carcass decompose naturally in the environment is not always feasible or preferred by the local jurisdiction. In some cases, animals are euthanized with specific chemicals (e.g., pentobarbital) that can harm scavengers including birds, coyotes, and sharks. When this happens, the carcass must be removed from the area and disposed of in a safe manner that prevents future risk to other wildlife or the environment. Safe removal methods include:

• Incineration (similar to pet cremation) 
• Composting 
• Rendering (recycling of animal parts)
• Burial in a licensed landfill 

Availability of these options varies depending on the location and can be costly depending on heavy equipment and transportation needs.

Planning for Disposal

Carcass disposal is often a collaborative effort involving multiple partners. If the animal is an endangered or threatened species, government agencies must consult with NOAA Fisheries to acquire disposal authorization. They should also coordinate appropriate methods with the local marine mammal response organization. NOAA Fisheries has developed best practices for local responders. 

Local jurisdictions across the country have specific requirements for carcass disposal. Some municipalities prefer the removal of all dead marine mammals from public beaches; others promote leaving carcasses in place to support the natural balance of the ecosystem. 

The stranding location’s geography or logistics can limit disposal options. Moving the carcass can increase the options for disposal if neighboring jurisdictions have additional resources or options (such as a landfill or rendering plant). However, removal takes time and may require heavy equipment, which is often expensive, challenging to organize on short notice, and restricted in certain areas. For larger whales, the availability of a pre-selected relocation site depends on the time of year and available resources. 

When towing a marine mammal carcass offshore, we can use drift modeling to identify an appropriate release site. Drift modeling uses current and wind data to predict the carcass’s likely floating path from the release site. Teams also consult with the U.S. Coast Guard to help prevent the carcass from returning to shore (restranding) or becoming a navigational hazard. All ocean-based disposal methods require authorization from the U.S. Environmental Protection Agency. Towing a carcass offshore requires significant planning and coordination, and unforeseen conditions can sometimes result in a carcass floating back to shore. 

Human Safety Considerations

Marine mammals may pose a health risk, as they can carry infectious diseases that can spread to people and pets. Responders may wear safety gear—such as protective clothing, gloves, face masks, and eye protection—to mitigate risks associated with handling and moving decomposing carcasses. 

If necessary, a safety officer can be designated to monitor on-scene conditions. They develop measures to ensure the safety of personnel and the public when working close to a marine mammal, especially when the response includes heavy equipment. When burying a carcass on a public beach, teams will establish a perimeter to ensure public safety around the heavy machinery and the burial hole.

Towing a large carcass away from its stranding site can be dangerous. Only trained experts experienced working with lines, straps, or chains under tension, should attempt to tow a carcass. Experts first evaluate the carcass’s condition and then select the appropriate equipment. 

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What Can You Do?

If you see a dead marine mammal, you can help experts respond:

• Give space: Do not attempt to touch, handle, remove parts, or return the carcass to the water.
• Keep pets leashed and at a safe distance: Do not let them approach, interact with, or consume dead marine mammals, to avoid disease transfer
• Immediately report it to local stranding hotlines and await further guidance from trained and authorized responders