Cetacean strandings and unusual mortality events: Why do cetaceans beach?

By Alejandro Fernandez Ajo, PhD student in the Department of Biology, Northern Arizona University, visiting scientist in the GEMM Lab working on the gray whale physiology and ecology project  

When a cetacean (whales and dolphins) is ashore or trapped in nearshore waters and cannot return to the open waters, it is considered stranded. Frequently, the stranded animal is in distress, dying, or dead. Although rare, the stranded cetacean can be a healthy animal trapped due to changes in tide or disorientation. Every year many cetacean strandings are reported from along the coasts around the world, and likely many more stranding events go unnoticed when they occur in remote areas. In all cases, the question is: why do cetaceans beach?

Southern right whales stranded at the coast of Peninsula Valdés, Patagonia-Argentina. Photo: Matias DiMartino / Southern Right Whale Health Monitoring Program.

There may be different causes for whales and dolphins to strand on beaches, either dead or alive. Understanding and investigating the causes of cetaceans strandings is critical because they can be indicators of ocean health, can help identify anthropogenic sources of disturbance, and can give insights into larger environmental issues that may also have implications for human health (NOAA). In this context, when scientists are analyzing a stranding event, they consider both possibilities that the event was natural or human-caused and classify strandings according to specific characteristics to study the causes of these events.

Types of cetacean strandings:

Live or Dead Stranding:

A stranding can involve live animals or dead animals if the death occurs in the sea and the body is thrown ashore by wind or currents. In live strandings, when they occur near urbanized areas, usually significant efforts are made to rescue and return the animals to the water; with small odontocetes, sometimes there is success, and animals can be rescued. However, when large whales are beached alive, their own weight out of the water can compress their organs and can cause irreversible internal damage. Although not externally visible, such damage can sometimes cause the death of the animal even after returning to the sea.

According to the number of individuals:

Single strandings occur when only a single specimen is affected at the time. The cetaceans that most frequently strand individually are the baleen (or mysticete) whales, such as right and humpback whales, due to their often solitary habits.

Mass strandings comprise two or more specimens, and in some cases, it can involve tens or even a few hundred animals. The mass strandings are more frequently observed for the odontocetes, such as pilot whales, false killer whales, and sperm whales with more complex social structures and gregarious habits.

Left: Single southern right whale calf stranded at the coast of Peninsula Valdés, Patagonia-Argentina. Ph.: Mariano Sironi / ICB. Right: Mass stranding of common dolphins in Patagonia-Argentina. Photo: www.elpais.com

Unusual Mortality Events

The Marine Mammal Protection Act defines an unusual mortality event (UME) as a stranding event that is unexpected, involves a significant die-off of any marine mammal population, and demands immediate response. Seven criteria make a mortality event “unusual.” Source: https://www.fisheries.noaa.gov.

  1. A marked increase in the magnitude or a marked change in morbidity, mortality, or strandings when compared with prior records.
  2. A temporal change in morbidity, mortality, or strandings is occurring.
  3. A spatial change in morbidity, mortality, or strandings is occurring.
  4. The species, age, or sex composition of the affected animals is different than that of animals that are normally affected.
  5. Affected animals exhibit similar or unusual pathologic findings, behavior patterns, clinical signs, or general physical condition (e.g., blubber thickness).
  6. Potentially significant morbidity, mortality, or stranding is observed in species, stocks, or populations that are particularly vulnerable (e.g., listed as depleted, threatened, or endangered, or declining). For example, stranding of three or four right whales may be cause for great concern, whereas stranding of a similar number of fin whales may not.
  7. Morbidity is observed concurrent with or as part of an unexplained continual decline of a marine mammal population, stock, or species.

The purpose of the classification of a mortality event as a UME is to activate an emergency response that aims to minimize deaths, determine the event cause, or causes, determine the effect of the event on the population, and identify the role of environmental parameters in the event. Such classification authorizes a federal investigation that is led by the expertise of the Working Group on Marine Mammal Unusual Mortality Events to investigate the event. This working group is comprised of experts from scientific and academic institutions, conservation organizations, and state and federal agencies, all of whom work closely with stranding networks and have a wide variety of experience in biology, toxicology, pathology, ecology, and epidemiology.

Southern right whale necropsy and external measurements. Source: Southern Right Whale Health Monitoring Program / ICB.

What can be learned from strandings and UMEs?

Examining stranded marine mammals can provide valuable insight into marine mammal health and identify environmental factors leading to strandings. Through forensic examinations, the aim is to identify possible risks to whales’ health and evaluate their susceptibility to diseases, pollutants, and other stressors. This information can contribute to cetacean conservation through informed management strategies. However, the quality of the data derived from a necropsy (the postmortem examination of carcasses) is highly contingent upon how early the stranding event is reported. As soon as the animal is deceased, decomposition starts, hindering the possibilities of detailed investigations of the cause of death.

Therefore, a solid network that can report and respond quickly to a stranding event is fundamental; this includes trained personnel, infrastructure, funding, and expertise to respond in a manner that provides for animal welfare (in the case of live strandings) and obtains data on marine mammal health and causes of death. Moreover, a coordinated international organization that integrates national marine mammal stranding networks has also been identifying as a critical aspect to enable adequate response to such mortality events. In many locations and countries around the world, funding, logistical support, and training remain challenging to stranding response.

In response to these concerns and needs, at the last World Marine Mammal Conference, which took place in Barcelona in December of 2019, The Global Stranding Network was founded to “enhance and strengthen international collaboration to (1) ensure consistent, high-quality response to stranded marine mammals globally, and (2) support conservation efforts for species under threat of extinction.” Monitoring marine mammal health worldwide can guide conservation and help identify priority areas for management (Gulland and Stockin, 2020).

What to do in case of finding a whale or dolphin on the beach?

When strandings occur, it is essential to know how to act. Unfortunately, untrained people, often with good intentions, can worsen the situation of stress and injury to the animal or can put themselves at risk of injury or exposure to pathogens. If you find a cetacean alive or dead on the beach, the most important things to do are:

  1. Record information about the location and the animal´s characteristics (the species, if known; the animal’s approximate size; and status (alive or dead)).
  2. Give immediate notice to the responsible authorities so that specialized help arrives as soon as possible. Report a Stranded or Injured Marine Animal.
  3. Keep at a safe distance: the animal may appear dead to the naked eye and not be. It is important to remember that cetaceans are wild animals and that in stressful situations such as strandings, they can try to defend themselves.
  4. Do not touch the animal: one of the causes of strandings is diseases; therefore, it is advisable not to contact the individuals to avoid exposure to potential pathogens.
  5. If the animal is alive, keep a distance from the animal, especially from its head and tail. Prevent children or dogs from approaching the animal.
  6. Keep calm and do not make noise that could disturb the stranded animal.
  7. Do not take the animal out of the water if it is on the shore or return it to the sea if it is on the beach: Such movement could cause serious injuries, or even death.
  8. Do not feed the animal or give it water: keep the blowhole clear because it is where they breathe.

Source: Whale Conservation Institute of Argentina

Important contacts in case of reporting a Stranded or injured Marine Mammal:

  1. National Oceanic and Atmospheric Administration
  2. Oregon Marine Mammal Stranding Network

References:

https://www.fisheries.noaa.gov/national/marine-mammal-protection/marine-mammal-unusual-mortality-events

https://www.fisheries.noaa.gov/insight/understanding-marine-mammal-unusual-mortality-events#what_criteria_define_an_ume?

https://ballenas.org.ar/programa-de-monitoreo-sanitario-ballena-franca-austral-pmsbfa/

https://globalstrandingnetwork.com/about

https://iwc.int/strandings

Proceedings of the workshop “Harmonizing Global Stranding Response.” (2020) World marine mammal Conference Barcelona, Catalonia, Spain. Editors: Gulland F and Stockin K; Ecs Special Publication Series No. 62.

Mazzariol S., Siebert U., Scheinin A., Deaville R., Brownlow A., Uhart M.., Marcondes M., Hernandez G., Stimmelmayr R., Rowles T., Moore K., Gulland F., Meyer M., Grover D., Lindsay P., Chansue N., Stockin K. (2020). Summary of Unusual Cetaceans Strandings Events worldwide (2018-2020). SC-68B/E/09 Rev1.

Cetaceans in the news

By Florence Sullivan, MSc Student Oregon State University, Department of Fisheries and Wildlife

It’s been a couple long, busy weeks here at the GEMM lab as my field season has wrapped up and new labmates are just getting started. There are students in the lab at all hours organizing, processing, and analyzing data. Much of our work investigating the spatial and temporal patterns of marine mammals around the globe takes long hours of parsing through information to bring you results. Systematic sampling is an important research tool but, sometimes, exciting discoveries just wash up at your front door.

Humpback Whale stranding in Puget Sound

http://westseattleblog.com/2016/08/stranded-whale-reported-south-of-fauntleroy-ferry-dock/

Just recently on August 7, 2016, a 39 foot, juvenile female Humpback whale stranded at the Fauntleroy Ferry Terminal in West Seattle, WA. This is very close to my home town, and a recent GEMM lab intern was in the area at the time, so we have a photo of this event for you!  The humpback came ashore while still alive, but despite efforts to keep it comfortable and wet, the whale died before the tide returned.

Humpback whale stranded at Fauntleroy Ferry Terminal, West Seattle. photo credit: Sarah Wiesner
Humpback whale stranded at Fauntleroy Ferry Terminal, West Seattle. photo credit: Sarah Wiesner

A cursory necropsy, conducted on site by researchers from NOAA fisheries and the Cascadia Research Collective, showed the animal had multiple internal parasites and injuries associated with beaching, as well as being in poor nutritional condition overall. There were also bites on the lower jaw consistent with killer whale encounters, and a pod of orca had been spotted in the area the previous day. Necropsies are an important source of data about the basic physiology and biology of marine mammals that is not accessible through any other means. The carcass was towed to a deep-water disposal site approved by federal and state agencies and sunk.  Humpback whale sightings in the Salish Sea have increased in the last five years. This, together with the fact that this juvenile was in poor nutritional condition, could indicate that there is competition for resources.

New Species Discovered!

There have been two new species of cetaceans discovered in recent months!

http://news.nationalgeographic.com/2016/07/new-whale-species/

http://www.npr.org/sections/thetwo-way/2016/07/27/487665728/mysterious-and-known-as-the-raven-scientists-identify-new-whale-species

The first exciting announcement was published in the journal Marine Mammal Science in July. Japanese fishermen in the North Pacific have long reported a small, black beaked whale they call karasu, “raven.” In 2013, Japanese researchers published a paper about this black, beaked whale variant of the sub-family Berardiinae using three stranded carcasses, but the sample size was too small to make any conclusions. Three years later there is strong genetic evidence that this is a new species of beaked whale based on (1) genetic analysis of samples from a stranded animal on St. George, Alaska (2) skeletons in a high school in Unalaska, Alaska, (3) skeletons in the Smithsonian archives, and (4) skeletons in other museum and institutional collections around the Pacific Rim. The species still needs to be described and named, but some researchers have suggested Berardius beringiae to honor the sea where it was found. What do you think?

This beaked whale stranded in the Aleutian Islands in 2004, and was measured by Reid Brewer of the University of Alaska Southeast.  Analysis of tissue samples later identified the whale as one of the new species. Photo Credit: Don Graves

http://www.smithsonianmag.com/smithsonian-institution/new-species-ancient-river-dolphin-discovered-exctinct-millions-years-ago-180960146/

The second announcement of a new species came from the Smithsonian Institution earlier this month. A skull of the newly-named Arktocara yakataga species was found more than 60 years ago near the present day city of Yakutat, Alaska. Obviously belonging to a prehistoric dolphin, the skull was kept at the Smithsonian’s National Museum of Natural History until new research found that it was actually a previously undiscovered species. A. yakatoga is thought to be a relative of the present day South Asian River Dolphin, and is both the northernmost, and one of the oldest dolphin fossils found to date. This new find is a reminder to everyone that not all discoveries are made in the field. Museum and archival collections continue to play an important role in the advancement of science and knowledge. Check out the link above to see some awesome artistic renderings of the new species, as well as a 3D scan of the skull in question.

Humpbacks vs Orcas

http://onlinelibrary.wiley.com/doi/10.1111/mms.12343/full

http://news.nationalgeographic.com/2016/08/humpback-whales-save-animals-killer-whales-explained/

Sounds like the next big B-Sci-fi movie doesn’t it? Well, this story is the latest to go viral on the internet. Published on July 20, 216 in the journal Marine Mammal Science, the study investigated accounts of humpback whales interfering with killer whale attacks. Researchers looked at 115 interactions between the two species. Humpbacks initiated 57% of the interactions, and 87% of these moments occurred when the killer whales were attacking or feeding on prey.  Surprisingly, only 11% of the prey in these events were humpback whales, while the remaining 89% ranged from other cetaceans to pinnipeds, to a sunfish! The authors suggest that the humpback whales were alerted to attacking killer whales in the area by vocalizations, and that this attracts them to the scene regardless of the species being attacked. Although kin selection (care for or defense of relatives to preserve your family’s genetics even though the action may be detrimental to self), or reciprocity (exchange between individuals for mutual benefit) might explain some of this behavior, the fact that humpback whales so often defended other species means that we cannot rule out the possibility of altruistic behavior.  This is a pretty fascinating read, and definitely opens up some new questions for researchers!

Humpback whales.
Humpback whales. Photo credit: Florence Sullivan