Saturday February 11, 2016 240 whales swam aground at a remote New Zealand beach.
On Friday February 10, 2016, 416 whales were found stranded and helpless on a crescent of land on New Zealand’s South Island called Farewell Spit in Golden Bay, over half of them already dead.
On both occasion, hundreds of volunteers worked tirelessly to ensure that the survivors are refloated on high tide back to the open sea.
Despite their heroic acts, over half of the whales that arrived the beach died. Some died upon arrival probably due to injury, some died later on due to dehydration. Volunteers tried to keep survivors alive by cooling them with water. Only a few hundreds were left alive to set afloat again.
New Zealand has one of the highest stranding rates in the world. On average, about 300 dolphins and whales strand each year but this recent event is one of the worst ever in New Zealand and around the world.
A total number of 656 pilot whales were stranded making this the second largest whale stranding event in history. The first was In 1918, when approximately 1000 pilot whales stranded on the Chatham Islands, this was the largest whale stranding in recorded history.
What is whale stranding and what could cause these intelligent mammals to beach themselves?
What is Whale Stranding?
Whale stranding or in general terms Cetacean stranding is a phenomenon in which cetaceans allow themselves to be beached or drive themselves ashore, usually on a beach.
Most stranding are of individual animals, but mass stranding are common and can involve hundreds of animals at a time.
That’s why we can say that stranding could be single or multiple.
Single stranding are often the result of illness, injury or old age. The end result is often death unless prevented by succesful human intervention.
Also, cetaceans that die offshore are likely to be carried to the coastline by currents or winds if they are not eaten by scavengers or decomposed by biological agents which will allow it sink to the ocean bottom to firm whale falls.
Multiple stranding involves the standing of multiple animals and this is rare but it has occurred severally over time. It is often followed by media coverage rescue efforts by selfless volunteers. An example of multiple stranding was given at the beginning of this write-up.
Causes of stranding
Several reasons for stranding have been proposed so we are going to be looking at the most significant ones.
1. Human activities.
Fishing with trawls or trawl nets, shipping and other human offshore activities can lead to stranding.
For example, one of these large mammals can get hit by a ship or get entangled in a fishing net. These sustain serious injuries that may result in them stranding.
Over fishing can leave whales hungry and nothing to eat. They become weak and unable to withstand the heavy winds and current of the sea and eventually finds themselves blown ashore.
Underwater explosions caused by sonar and seismic testing can have a devastating impact on whales.
The loud noise from the explosions can scare or disorient them affecting their navigating abilities. It can also damage their hearing and affect their ability to communicate.
Evidence has shown that on some occasions cetaceans have stranded shortly after military sonar activities were carried out in the area. The military uses the sonar to detect submarines.
Whales stranded due to sonar activities have been observed to have internal injuries unlike those that stranded due to natural causes.
2. Natural and environmental causes.
Like was Earlier said, weakness due to old age and illness are also causes of stranding.
Whale behaviour is also a cause. When Hunting, they tend to follow their prey wherever including shallow waters.
In some cases, killer whales have been known to scare other whales, making them move towards the shoreline.
According to a theory by scientists at the university of Tasmania, these cetaceans, due to the nature of their echolocation system find it difficult to
pick up very gently sloping coastline.
It is a habit or custom for larger cetaceans to follow fast-moving dolphins and porpoises that can maneuver easily where the larger mammals could become trapped and eventually stranded. This type is commonly called follow me stranding.
Stranding is a very complex event. In most cases, whatever may have caused the stranding remains unknown. Scientists and researchers have proposed many theories to try to explain beaching, but the question remains unresolved.
One certainty is that cetacean stranding would continue to occur because for now it cannot be prevented by man.
We can only try to reduce our human activities at sea to make it a safer place for Marine animals.