Frequently asked questions
Large baleen whales and smaller dolphins
The term cetacean is the collective name for several orders of sea creatures including the baleen whales and toothed whales (dolphins and porpoises). Several species are found in the North Sea:
- Harbour porpoises
- White beaked dolphins
- Common bottle nosed dolphins
- Short-beaked common dolphins
- Atlantic white-sided dolphin
- Common minke whales
- Long-finned pilot whales
- Humpback whales
- Fin whales
Some species whose ranges border the Southern North Sea occasionally stray into these waters. This includes:
- Sperm whales
- Sowerby's beaked whales (North Atlantic or North Sea beaked whale)
- Striped dolphins
- Bottlenose whales
These animals are used to deep waters and feed on deep sea foods such as squid. Therefore they struggle to survive in the North Sea.
Does human activity play a role?
Porpoises and other cetaceans can become stranded due to disease or weakness but human activities can also play a role. Examples of human activity-related issues include disturbance such as underwater sounds, pollution (plastics), toxins (PCBs, POPs and heavy metals), by-catch (during commercial fishing operations porpoises and other non-target species can become caught in nets and suffocate), damage to hearing (caused by underwater construction projects such as windmill parks and seismic research) or collisions with ships. It is often the case that there are many contributory factors and sometimes the precise cause of the stranding is not determined.
Individual or mass strandings
Porpoise strandings usually involve individual animals reflecting their predominantly solitary existence. In contrast, species such as the long-finned pilot whale and sperm whales live in family groups or pods and strandings typically involve multiple animals. When two or more animals strand in the same location it is referred to as a mass stranding – with the exception of mother-calf pairs.
To determine the cause of death
The main purpose of the investigations commissioned by the Ministry of Agriculture Nature and Food is to determine the cause of death of the porpoises that get washed ashore and more specifically to identify cases in which humans activities are likely to have been involved. There are often many factors that contribute to the death of an animal and in some cases the cause of death remains unclear.
The consequences of hearing damage
Cetaceans depend on their hearing for hunting prey, communication, the detection of predators and for navigation. Disturbances or hearing damage can have serious consequences for individuals and ultimately the whole population.
The human threat
Cetaceans can be exposed to many human threats as their territories often overlap with our marine-based industrial and leisure activities. In recent decades there has been an enormous increase in our presence in the marine environment through increased shipping, the construction of off-shore wind farms and additionally through rising sea temperatures. Sadly, when shipping routes traverse cetacean territories it is almost inevitable that collisions will occur.
Collisions and sound pollution
In the Netherlands in 2011, 2012, 2013 and 2015, four whales (3 rorquals and a common minke whale) were found on the bow of container ships entering Rotterdam harbour. The construction of off-shore wind farms and seismic research are both sources of underwater noise pollution and can cause hearing damage in cetaceans. Changes in sea temperature can affect currents which have an impact on the migration routes of cetaceans and their food sources. The impact of such human activities depends on their extent and varies between species, reflecting differences in territories and migration patterns.
Environmental indicators
There is public and political support for research into marine mammal strandings both in the Netherlands and abroad. This has been evidenced by the large amount of interest shown by public and the media during recent stranding events. Additionally, the position of cetaceans at the top of the food chain means that they can be used by scientists as indicator species for the ecosystem in which they live; changes can be reflected in altered ecology, geographical range and health status of these species.
Check if the animal is alive
Each year approximately 600 porpoises become stranded on Dutch shores. Local authorities are required to report each case and take charge of the carcase. The field work is typically carried out by enthusiastic volunteers who are often affiliated with Sea Mammal First Aid groups, sanctuaries, and animal welfare charities or beachcombers.
What happens when a stranding is reported?
The volunteer-run Dutch Strandings Network responds to reports of stranded porpoises and takes the appropriate next steps: If the stranded animal is alive, SOS Dolfijn, a marine mammal rescue centre, take over the case. The Faculty of Veterinary Medicine is informed when a fresh (recently deceased) carcass is reported.
When is necropsy carried out?
The volunteers of the Strandings Network contact the stranding investigation team at the department of pathology at the Faculty of Veterinary Medicine to discuss whether or not a carcase is suitable for further investigation: This typically depends on the state of decomposition and can generally be reliably judged based on photos.
What should you do if you find a stranded porpoise?
If you come across a stranded porpoise you should inform the Strandings Network straight away; the local representative will help to determine the urgency of the situation, informing us here at the Faculty of Veterinary Medicine at Utrecht University if the carcass is fresh.
If you find a living porpoise, whale or dolphin then you should contact SOS dolfijn on the emergency number: +31 (0)6 65 09 85 76. Speaking clearly, repeat your name and a contact number twice on the voicemail and you will called back immediately.
For more information visiting stranding.nl or waarneming.nl.
Dolphins and whale strandings are rare in Dutch waters
As this sort of stranding is thought to be fairly rare in the Netherlands, investigations into the cause of the stranding are handled on a case by case basis. In recent years there appears to have been an increase in such events for example in January 2016, six sperm whales were beached on the Dutch Island of Texel and two beaked whales were found dead in the province of Zeeland.
Investigating other species of whales
The increased media attention and public awareness of whales in Dutch waters, combined with the scientific curiosity of researchers in this field, have secured more financial support for research into other species of whales. This work, supported by the Ministry of Agriculture Nature and Food is largely carried out by volunteers.
Whale Stranding Protocol
After the tragic plight of the humpback whale Johannes, which stranded on the sandbank off the coast of Texel in 2012, the Ministry for Agriculture Nature and Food commissioned a protocol to be followed when living whales and dolphins become stranded on the Dutch coastline. In the sad event that these animals die, it is a valuable opportunity for pathologists to sample and study fresh tissue from these exceptional sea creatures. Cetaceans measuring more than 5 metres in length cannot be transported due to their weight and size so whilst smaller dolphin necropsy can be carried out at the Faculty of Veterinary Medicine, whale carcasses are dissected in the field.
Fresh enough to be investigated
Carcasses that are minimally decomposed are sent to the Faculty of Veterinary Medicine in Utrecht for pathological investigation and sampling by the strandings team. Suitable carcasses are tagged so that the date and location of the stranding can be recorded along with other necropsy data. We only investigate dead stranded animals: Cases involving live stranded porpoises, whales or dolphins are managed by SOS dolfijn.
Stranding expertise hub
The Faculty of Veterinary Medicine at Utrecht University is the only educational institute in the Netherlands where veterinarians are trained. The Department of Veterinary Pathology collects and presents data about the working of cells, tissues and organs in health and disease in a wide range of animal species. This means that we have much knowledge about disease processes in wildlife and other species of animal and we use this is our investigations of stranded animals.
Recognising patterns in strandings
This vast knowledge of veterinary pathology, in combination with state-of-the-art facilities and a central location makes the veterinary school’s pathology department the perfect base for the stranding project’s research activities. All necropsies carried out on porpoises found stranded in the Netherlands throughout the year are now performed by our strandings team in one location. This large bank of strandings data in Utrecht means that patterns in strandings and causes of death can be recognised, communicated, and promptly addressed.
Whale and dolphin strandings
In addition to the hundreds of porpoises washed up on the Dutch coast each year, whales, dolphins and other marine mammals occasionally strand on these coastlines. Working closely with the National Stranding Network, the Ministry of Economic Affairs and several other partners, the Faculty of Veterinary Medicine has a central role in the investigation of these events.
The Dutch government funds research into porpoise strandings
Stranding investigation at the Faculty of Veterinary Medicine is funded by the Ministry of Agriculture Nature and Food; the government wants to shed light on the cause of death of porpoises stranding in the Netherlands and is particularly interested in determining what role human activities play in these events.
Since the Agreement on the Conservation of Small Cetaceans of the Baltic and North Seas (ASCOBANS) came in to force in 1991 the Netherlands has been committed to conserving porpoises in Dutch waters. Porpoise population monitoring which includes the investigation of stranding events is covered by a clause in Dutch law which will be reviewed in 2020. Additional monitoring such as aerial surveys and diet and pollution studies is performed by Wageningen Marine Research (previously IMARES).
The current funding covers our research into porpoise strandings; however, investigation of strandings involving other species of whales and dolphins is largely dependent on volunteers and contributions. By co-ordinating these investigations, the porpoise stranding team in Utrecht lends its scientific knowledge, logistical resources and practical experience to this work. Due to the perceived increase in the so-called ‘unique strandings’ involving other marine mammal species in recent years, we are currently seeking to secure permanent funding for this valuable work.
Support us!
It is possible to support this unique research into whale and dolphin strandings by donating to Vrienden Diergeneeskunde.
Renewable Energy
The remaining material is appropriately disposed of. European waste disposal laws dictate that material of animal origin must be disposed of in a hygienic and welfare-friendly manner. What remains of the porpoise carcasses is collected by Rendac, a company specialising in this form of waste handling.
The end-product of this disposal process is used as an environmentally-friendly combustible fuel.