Marine Mammal Strandings and The Role of The Veterinarian

Nick Gales, Rupert Woods and Larry Vogelnest


1.1 General

Marine mammal strandings, particularly those involving large numbers of whales or dolphins, attract a vast amount of public and media attention. These events are often the scene of impressive mobilisations of heavy equipment, volunteers and a variety of experts who attempt to contribute to the rescue effort. Knowledgeable veterinary expertise is a significant component of any rescue and the veterinarian at a stranding is likely to find themselves in a high-profile, challenging, operational and advisory role. Their role can be as varied as the strandings themselves and include aspects of clinical examination or necropsy and assessment, drug selection and administration, euthanasia and tag attachment. It can also be controversial. The media increasingly seek early advice on the likelihood of human causes of the stranding such as potential links to seismic or military acoustic activities that may have occurred in the vicinity. Similarly, advice to euthanase an animal may meet with polarised views. More commonly, however, veterinarians will be asked to advise or assist with health assessments and interventions for single stranded cetaceans or pinnipeds. In all eventualities, the way to maximise the positive contribution of the veterinarian is to ensure that they understand their role and the role of others, and give advice that matches their experience, knowledge and capacity in circumstances that may be novel and at times overwhelming.

Very few comprehensive texts have been produced on the wider topic of strandings; Marine Mammals Ashore: A Field Guide for Strandings (2nd edn) by Geraci and Lounsbury (2005) and the University of Sydney’s Post Graduate Foundation in Veterinary Science Marine Wildlife, Proceedings 335 (2000) are probably the most useful. Within the confines of this chapter it is not possible to provide a detailed clinicians’ guide to diagnosis, treatment, sample collection and follow-up for all stranding scenarios. Rather, we more modestly aim to provide veterinarians, particularly those less familiar with marine mammal anatomy and physiology, with a reasonably brief and accessible summary and guide that, augmented with guides like that of Geraci and Lounsbury (2005) and the information in Chapters 17, 18 and 19 of this volume, will help them understand how and why they might best contribute to positive outcomes from marine mammal strandings. Good guides to identification and basic background biology of commonly stranded animals can be found in Baker (1999), Bryden et al. (1998) and Carwardine (1995).

We will discuss in general terms the issues of strandings of all marine mammals. Although single stranded cetaceans and pinnipeds ashore are much more common, the prognosis for single stranded cetaceans is generally poor and mass strandings often require greater veterinary involvement. For this reason, the focus of this summary will be most relevant to cetacean mass strandings.

Inexperienced veterinarians should be encouraged, once they have made an initial assessment of a stranded animal, to contact an experienced veterinarian for advice on how to proceed. This often helps enormously and can contribute to a more rapid and humane outcome. Most wildlife agencies have stranding policies and procedures and contact details for experienced marine mammal veterinarians in each state.

1.2 What is a stranding, and why do marine mammals strand?

For the purpose of this chapter we define a stranding as any of the following: any dead marine mammal on a beach or floating near-shore; any live cetacean (whale or dolphin) or dugong on a beach or in water so shallow that it is unable to free itself and resume normal activity, or any live pinniped (seal, fur-seal or sea-lion) which is unable or unwilling to leave the shore because of injury or poor health.

By far the most common form of stranding involves single animals. The causes of death or debility in these circumstances are highly varied and often include more than one factor operating simultaneously. Natural causes such as disease, parasitism, biotoxins, predator attack, animals being trapped by outgoing tides or dependent infants separated from their mothers have been widely reported, as have human factors such as vessel-strike, entanglement, shooting and pollutant contamination (Dierauf & Gulland 2001; Perrin & Geraci 2002). Typically, single strandings occur as unrelated events, but on occasions patterns of strandings may occur, indicating a larger-scale process. These patterns may be associated with the normal distribution, migration or reproduction of the species, such as patterns of strandings of juvenile fur-seals soon after weaning. Of greater concern are unusual mortality events that may manifest from human causes such as over-fishing or climate change effects, or be part of the rapid spread of an infectious agent in a marine mammal population.

The mass stranding of marine mammals is a particularly puzzling phenomenon generally restricted to cetaceans. While dugongs (Dugong dugong) have been recorded to mass strand in response to unusual tidal or storm events, it is the off-shore, gregarious toothed cetaceans such as pilot whales (Globicephala spp.), false killer whales (Pseudorca crassidens) and sperm whales (Physeter macrocephalus) that most commonly mass strand in Australia. These strandings consist primarily of apparently healthy animals, sometimes numbering in the hundreds, which strand as a group over periods of less than an hour to a few days. The media like to suggest that the cause of these events is a great scientific mystery—while it is true that the circumstances leading to a particular mass stranding are varied and extremely difficult to elucidate, the simple reason for mass strandings involves the strong social herding behaviour of the species involved. More specific contributing factors such as disease (of a subset of the animals), confusing bathymetry (ocean depth and topography), tides and rough seas are likely to be important in determining why a group of off-shore animals find themselves in close proximity to the shoreline.

While the beaching of a fully aquatic mammal like a cetacean or dugong is a clear aberration, determining when a pinniped that is hauled-out on land represents a stranding (by the above definition) can be more difficult. Extended periods of time ashore for the purpose of resting, moulting and reproduction are normal behaviours for these mammals and, while they generally frequent regular haul-out and breeding sites on relatively remote islands, they will come ashore quite regularly in areas where they may encounter people. A reluctance to leave the shore (part of the definition of a stranding for a pinniped) may also be entirely normal; e.g. bulls may be establishing a breeding territory, a southern elephant seal (Mirounga leonina) may be hauling out to moult, exhausted animals that have spent a long time at sea, those that may be used to humans. These animals may ignore encouragements to move or may respond aggressively. In many cases, where seals come ashore on public beaches the issues are more about management of human behaviour (and their dogs) than about management of the animal. When the reason for the seal being ashore is medically or physically based the underlying causes, as with cetaceans, are highly varied and include factors such as disease, parasitism, biotoxins, starvation (particularly following weaning) and predator attack, as well as human causes such as vessel-strike, entanglement and shooting.

1.3 What happens to marine mammals when they come ashore?

Obligate marine species such as cetaceans and sirenians (dugongs and manatees [Trichechus spp.]) evolved in a medium where they experience little of the gravitational consequences of mass and with a thermoregulatory system that enables them to live in waters that are usually substantially cooler than their core body temperatures. Being ashore instigates a rapid series of physical consequences that, without intervention, is certain to lead to death. The resultant physiological consequences and pathology will act additively with any potential preexisting pathology that may have led to the stranding, and may confound and obscure a veterinarian’s or pathologist’s attempts to determine a primary reason for the stranding. These changes are often difficult to see and a clinical examination can be frustratingly uninformative.

For the pinnipeds, which are used to periods ashore, a disease or injury that prevents them feeding effectively at sea will ultimately lead to dehydration and starvation. A clinical examination of these animals may provide more familiar cues to the non-specialist veterinarian, but the challenge of handling these potentially dangerous creatures often limit such endeavours (Chapter 17).

1.4 Why should veterinarians attend a stranding?

There are a number of motivations why people intervene at strandings. Much of what we know about marine mammals, particularly about some of the more cryptic off-shore species like beaked whales (Ziphiidae), has been learnt by sampling and studying animals that we find on our beaches. The scientific aspects of taxonomy, anatomy, physiology, biology and pathology in particular have relied to some degree upon such opportunities. Increasingly, in recent times, the pathology and behaviour of marine mammals ashore has provided our first warning of off-shore problems of natural origin (e.g. algal blooms) or human origin (e.g. exposure to high sound sources and fisheries interactions). Thus, science can inform and serve conservation. While many veterinarians are activity involved in this contribution to science and conservation, their primary role, and hopefully motivation, is perhaps more fundamentally based on the welfare of the individual animals.

The role of the veterinarian in the clinical assessment, treatment or euthanasia of stranded animals is fundamental to optimising their welfare outcome. Something of a conundrum exists here. In most cases, the mortalities associated with strandings are a normal part of that species’ life history. Wild animals die all the time from the many mechanisms that regulate their populations. Veterinarians do not spend their time at seal colonies assessing and treating the many ill and dying animals that are a normal part of any breeding season. So why attend to marine mammals that happen upon our shores in view of the public? While the scientific and conservation gains might be easy to justify—and be a critical part of the veterinarian’s role—why is a welfare outcome such a product of geography and proximity to humans? The answer is perhaps two-fold. First, to some extent our intervention can be seen as in some way redressing the balance of our negative impacts on marine mammals and their environments. The second and more compelling reason for veterinarians is that we are trained and able to improve the welfare outcomes for suffering animals that are so dramatically placed before us on our coastline. To do so is part of the general public response and expectation, which is largely based on concern and empathy with the plight of these stranded mammals.

1.5 Australian stranding response networks

Tremendous advances have been made in Australia over the past 20–30 years in preparing for and responding to stranding events. Strandings occur in all states and the Northern Territory but the southern states, especially Tasmania, experience the highest frequency of strandings and mass strandings in particular. Operational responsibilities for dealing with stranding events lie with the various fauna authorities in each state or territory. Most states manage mass stranding events with a formally established Incident Control System (ICS), such as those used for bushfire response. This system implements a clear hierarchical structure with an Incident Controller (IC) in overall charge and responsible for all decisions. For the veterinarian, the IC or their designated nominee is the ‘client’ and represents the ‘owner’ of the animals, which is the state. The advice and operational role of the veterinarian is often a key component of a successful outcome, but it is essential that these roles are conducted within the ICS framework. The IC must distil advice from wildlife specialists, veterinarians and experienced volunteer groups and balance these with operational, planning and logistics priorities. Consequently there may be occasions where veterinary advice is not followed. On these occasions it is important to understand the decision that has been made, support the consensus and move on.

Co-evolving with the sophistication of the response from state agencies has been the involvement of voluntary non-government organisations. The details of these voluntary organisations differ among states, but the model of groups working within an ICS framework is similar. These volunteers generally represent an enthusiastic resource with some training and experience. They can be a great asset to the veterinarian in assisting and providing informed feedback on the animals they are responsible for. These types of voluntary groups are generally mobilised for mass stranding events and are also commonly used to monitor pinnipeds that come ashore.

Veterinarians are a key part of any stranding response. The first role of the veterinarian at a single or mass stranding event should be to identify the IC or responsible state government officer and discuss how they can most effectively contribute to the response effort.


2.1 Work flow

As discussed above, the challenges facing a veterinarian and the areas in which they can contribute vary enormously with the taxa involved and whether the incident involves single or multiple individuals. This section provides a guide to help the veterinarian work through the processes of:

  • initial assessment;
  • stabilisation of the animals;
  • clinical examinations;
  • clinical pathology;
  • therapeutic and other intervention options;
  • considerations for immediate release, rehabilitation or euthanasia;
  • marking and post-release monitoring;
  • necropsy.

In conjunction with the representatives of the state authority, the veterinarian may also have a key role to play as mediator between agency staff, onlookers, volunteers and the media.

2.2 General principles

Fundamental to the correct management of a stranded marine mammal is correct identification of the species involved. This is particularly important for pinnipeds. Knowledge of the biology of the species, particularly in relation to distribution and range, seasonality of breeding, reproductive strategies, moulting, migration and social ecology will aid the decision-making process. Useful guides include Baker (1999), Bryden et al. (1998) and Carwardine (1995). If the identity of the species involved has been established, it is often useful for the veterinarian to read up on the species’ biology prior to attending the animals.

Stranded marine mammals, particularly cetaceans and sirenians, are typically in a highly compromised state when they are examined. Much of the clinical picture can be as much a result of being beached as it is of any pre-existing or stranding-induced pathology. Consequently, these clinical assessments should be interpreted with caution and where possible the benefit of the doubt should be given to the animal. It is remarkable how an unresponsive beached cetacean, for which a veterinarian might determine a poor prognosis, can improve rapidly when held for a short period in shallow water.

2.3 Mass strandings: cetaceans

2.3.1 Step 1: determine your role

The essential first step for the veterinarian is to identify the IC (or equivalent) and seek advice on what role they might play. It is most important that the veterinarian’s skills are best utilised, so it is important to avoid the temptation of getting involved in the general rescue effort of stabilising animals on the beach (unless there are very few people available).

Another key role is to ensure their own safety and that of others. Mass strandings in particular are extremely dangerous and it is important that this be recognised by the veterinarian. Times of highest risk for the veterinarian include clinical assessment and specimen collection (use extreme caution when working around the head or tail of the animal); moving and release of animals (rope entanglement and drowning); necropsy (slippery, often blunt knives and poor hygiene) and; at all times, exposure to the elements. People caught up in the emotions of dealing with stranded animals frequently ignore their own health and safety. Rough seas, rocks, heat, cold and the sun all pose significant risks. Although uncommon, the potential for zoonotic infections associated with marine mammals, particularly pinnipeds, must also always be considered.

2.3.2 Step 2: stabilise animals

Once human safety issues have been dealt with under the ICS, the stabilisation of animals will be the primary focus of the IC. This process need not involve the veterinarian. The first two priorities are likely to be to attempt to prevent any remaining free-swimming animals from stranding and to remove animals from the surf zone (onto the beach or out to sea).

Where possible, cetaceans should be placed into a position where they can be treated safely, both for the animal and personnel. If an animal is in shallow water and there is no significant surf it can be held gently in the water with its head facing out to sea. Such a circumstance minimises the physical trauma associated with a stranding. Where an animal is in a surf zone, on rocks or already beached, it should, if possible, be laid belly-down on reasonably level sand. Holes should be dug for its pectoral flippers.

Handling and transport of cetaceans has been reviewed (Geraci 2000). The IC and state authority at the stranding will have had experience in lifting and moving animals. Whales up to about 2 tonnes are routinely lifted with specialised slings, inflatable pontoons and heavy equipment. Live cetaceans should never be pulled backwards in the water, nor should they be rolled on land. They should never be dragged or towed out to sea by their tail stock. If animals cannot be moved, they should be made as comfortable as possible while waiting for the tide to come in. If they cannot be refloated they should be euthanased.

2.3.3 Step 3: rapidly assess and individually identify patients

The scene at mass strandings, even with well-organised responses, often appears chaotic. The number of animals may often be overwhelming and there are often many people taking what action they can with animals that are beached or beaching. For the veterinarian to make sense of much of the data they will collect during the stranding response (clinical examinations, clinical pathology, knowledge of the fate of the animals etc.) a critical first step is to ensure that all animals are temporarily marked to identify and track individuals, that their location both on the beach and relative to one another is recorded and, if known, the order in which they stranded. This is a normal part of the management of mass strandings and most state authorities have kits that include temporary tags (usually SC ‘spaghetti’ tags or coloured ribbon with numbers written in permanent ink, to be tied around the tail stock) and pro formas. These tasks are generally undertaken by someone other than the veterinarian, usually a marine wildlife officer or equivalent from the relevant state authority.

The rapid assessment is best conducted by a veterinarian and is used to prioritise the allocation of resources. In conducting the assessment it is important to remember that a stranded cetacean may or may not be diseased, but it is always injured or compromised to some extent by the stranding event itself. Three simple categories are useful: 1) most likely to survive; 2) less likely to survive (injured or weakly responsive); 3) dead.

Along with the individual number assigned to each animal, a colour category can be assigned for each of the three categories. The separation of the first two categories is not simple as a beached cetacean will inevitably develop respiratory fatigue and distress and will suffer superficial and musculoskeletal damage. The magnitude and rate at which this damage occurs is greater in larger animals. These changes are difficult to measure and we know little about their effects upon the animal’s survival. If in doubt, assign the higher category. The combination of records of careful and systematic clinical evaluations and of the eventual fate are a logical approach to improving our ability to predict the fate of a stranded cetacean. The assessment is primarily visual and relies mainly on behavioural criteria (see 2.3.5).

Maximum resources should initially be directed and ranked towards animals in the two live categories. If, during the process of the rescue operation, a subsequent clinical investigation determines a different category from the one ascribed during the rapid assessment, the animal’s colour band should be changed but its identification number must remain the same.

It is important to remember that the initial assessment is merely that. Repeated assessments of each individual are far more useful in assessing the prognosis for return to the sea. The single most important role of the veterinarian is to ensure that this longitudinal assessment occurs and the data are available for decisionmaking.

2.3.4 Step 4: first aid

First aid for stranded cetaceans should aim to limit further injury and maintain the animals’ homeostasis (maintain it in a non-stressful comfortable position and provide supportive care) as well as possible until further action is possible (Table 3.1). It will generally be applied by the volunteers attending a stranding, under the direction of the IC.

Table 3.1 Guide to first aid for stranded cetaceans

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May 28, 2017 | Posted by in GENERAL | Comments Off on Marine Mammal Strandings and The Role of The Veterinarian
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Effect of stranding

First aid measure


Pour cool water over dorsal fin, pectoral fins, tail fluke and head region. Do not cover these areas to encourage evaporative cooling.

Provide shade cover over the animal.

Respiratory difficulties

Clear and protect the blowhole from sand and water.

Position in ventral recumbency.

Move into water if possible.

Skin trauma (sun and physical)

Move from rocks or other solid sharp substrates.

Protect from sun and wind by covering with light coloured wet cloth or similar material.


Provide shade and cover with wet sheet or similar material.

Keep eyes and blowhole moist.

Tube with oral fluids.