Stranding Of Marine Mammals
By Mermaid Tracey
stranded 1
 
Stranding of Marine Mammals - part 1

If you live by the sea, you may encounter some marine animals stranded on a beach or in difficulties. What should you do in this situation?

Introduction

What is the definition of a stranded animal?
The Marine Mammal Protection Act defines it as:
Any dead marine mammal on the shore or in the water.
A live marine mammal on the shore unable to return to the water.
A live marine mammal that is on the shore and in need of medical attention.
A live marine mammal in the water, unable to return to its natural habitat without assistance.

Is there only one stranding type?
Stranding events fall into two categories.
Solitary stranding: when one dolphin, porpoise, whale or seal comes ashore, either alive or dead, and is in need of intervention.
Mass stranding: involving two or more stranding at the same time, in close proximity to one another.
Seals and baleen whales do not mass strand.

What type of animals are affected by stranding?
Stranded marine incidences do not only apply to dolphins, porpoises, whales, sea lions, sea otters and seals but can also include marine reptile sea turtles too.

Wht do marine animals strand?
In some cases the true cause of exactly why Marine mammals strand remains clouded in mystery. Although through history we see many accounts of single and mass stranding, the frequency and scale (often in record numbers) of what we are witnessing to date leaves us questioning whether this is indeed a natural phenomenon.
In many cases of mass stranding, it is often wrongly assumed that these creatures are merely committing suicide. Mass stranding is neither 'suicide' nor a 'natural phenomena'.

Theories as to why they strand
There are many valid theories as to why marine mammals strand. In the event of a single stranding, the cause is often easier to pin point as in most cases the individual involved may exhibit tell tale signs of malnutrition, illness or injury. Mass stranding events are a lot more difficult to assess, especially when apart from one or two in the pod exhibiting good cause, the rest appear to be in perfect health. In the case of a mass stranding, strong social bonds may be a key factor.

Species known to mass strand live in tight pods where there is safety in numbers. They are able to evade predators and hunt more effectively in a group. A dominant individual may venture into shallow waters for various reasons, and the whole pod will follow suite, wandering out of normal range and run ashore accidentally, leaving the group trapped and ultimately beached at low tide.

Natural instinctual reasons may drive them in; to give birth to their young or to hunt for seasonal food; it is not unusual to find a pod trapped near shore after getting caught up in the thrill of the chase (bottlenose dolphins have been known to almost beach themselves when catching fish in very shallow water). One or two members may be in a weakened state caused by old age, starvation, or illness (parasites, viruses, pneumonia, and ingestion of poisonous algae) and come to shore to die. Encounters with predators such as sharks or attacks from the same species may also drive them inshore. Many are deep sea creatures who become disorientated and confused in low water. When there is no effective option to return to deeper waters, panic and stress leaves them too exhausted to swim.

In South Africa, natural events such as whale migrations (May to October) and the Sardine run (April to July) bring increased numbers of marine animals, including predators to our coastlines.
Some coastlines see more stranding events than others where geographic features may be a factor.

These locations have been found to share common traits; hook shaped land masses, shallow shelving or sloping beaches and jutting landforms. Confusing underwater topography and unusual configuration of headlands may all be instrumental in causing navigational errors for deep sea creatures.

Pelagic, off-shore species (Atlantic white-sided, common dolphins, pilot whales and Risso’s) that commonly strand are not accustomed to strong tidal fluctuations and become trapped when the tide recedes. Rough weather, severe rip currents, electrical storms, heavy seas; unusual tides; environmental events (tsunamis etc.); deep sea seismic activity (earthquakes); changing weather patterns; anomalies in the magnetic field; to name but a few; may affect marine mammals by blurring their sense of direction and throwing them off course.

What cannot be ignored and could well be the determining cause of the recent increase of reported stranding events is human impact.

Increased ocean traffic often leads to ships or boats striking marine mammals; causing severe injury. Reports of animals sustaining injuries from man-mad debris in the ocean; oil spills; industrial by-product contamination and intensive fisheries operations are on the rise. Entanglement in fishing nets and gear are the biggest killer of whales and dolphins across the globe, causing terrible injury and death by suffocation. Toxic nuclear radiation spills, mercury poisoning, the likes of what has been seen in Fukushima (Japan) have tremendous impact on marine life. Sonar mapping; surveys for oil and gas; naval manoeuvres involving high-intensity low frequency sonar; military exercises using loud underwater explosions may be instrumental in causing auditory trauma and loss of echolocation in cetaceans.

This does not bode well for the future well-being of marine mammals that rely largely on echo location to survive in their own natural habitat.

What shall I do if I encounter a live stranding of dolphins, porpoises or whales?
Each stranding is different and many unique challenges are often encountered. There are no set rules to adhere to when encountering this stressful phenomenon, but certain principles that have proved extremely helpful with previous cases can be utilized to successfully protect, stabilize, re-float and ultimately release mammals in distress.

Sometimes you will need to use your own counsel to try to help animals in distress if no marine rescue can be reached, other times, rescues may ask you to do a few basic things.

The following articles are only a guideline regarding the essential steps that could be instrumental in saving lives.

They do not in any shape or form certify anyone as a marine mammal rescuer. Always consult local authorities and local rescue organisations before attempting to help an animal.

*Please note that if you do decide to assist a stranded individual, you do so at your own risk. Mermaids 4 Cetaceans and any rescue organization cannot be held responsible for any damage or injury suffered to persons or property resulting from assistance of a stranded animal.

 

Further reading