A total of 48 short-finned pilot whales stranded at Sabu Island, East Nusa Tenggara

A total of 48 short-finned pilot whales (Globicephala macrorhynchus) stranded at Sabu Raiju (Sabu Island, East Nusa Tenggara) last night (Monday, 1 October 2012). I first received the information from Veda Santiaji and Kimpul Sudarsana from WWF Indonesia. They in turn received the first-hand account from Alexander S. Tanody (The Nature Conservancy, Savu Sea), the closest field-based office and NGO from the stranding event. 

 Photo @ Sabu government via WWF Indonesia

According to Alexander, around 7pm on Monday (1 October 2012), 44 pilot whales stranded at Deme Village (Liae District, Sabu Raijua Regency). Related government agencies went straight away to the location. By 4 o’clock in the morning, 4 whales were released back to the sea, while many of the 40 pilot whales were already dead. The whales were about 2-9 m long. Two additional whales (assuming the same species) were also found stranded at the neighbouring village. 

Many people in Indonesia are still unfamiliar with stranding events. In addition, due to the remoteness of the location, high mortality rate during stranding events is understandable. FYI, I have posted tips to handle stranded cetaceans here (Indonesian version  and English version).

Logically, my friends asked me why this event happened. Not an easy question. I cannot set aside the possibility of pathological reason behind the stranding event. An autopsy needs to be done to see if the animals were ill, and thus stranded. Below is my analysis of the possible cause(s) of the event. 

1.       Pathological reasons

Several pathological reasons contribute to cetacean stranding:

a.      Parasite

b.      Internal haemorrhage or acute embolism (bubble lesions) due to man-made sonar and seismic activities

c.       The animal swallowed foreign objects (e.g., plastic) which clogged its system, causing disorientation and stranding

Necropsy needs to be done to justify pathological causes. Cranial and ear necropsy may reveal internal haemorrhage due to sonar or seismic activities (Cox et al. 2006; Yang et al. 2008) and possible parasite presence (Morimitsu et al. 1987). Necropsy targeting digestive system may reveal the presence of foreign objects (e.g., plastic). Necropsy targeting other internal organs (e.g., kidney, liver and lymph nodes) may unearth acute embolism or bubble lesions which may indicate the impact of seismic or sonar activities (Jepson et al. 2003).

Some pathological reasons (such as foreign objects and parasites) might only influence several animals in a pod, in this case short-finned pilot whales, instead of the whole pod. Yet, due to the tendency of pilot whales (and other Odontocetes) to flock together, it can take only one sick animal to strand and lead the rest of the group stranded as well. On the other hand, man-made sonar and seismic activities may cause internal bleeding or acute embolism across the entire pod. 

Earthquakes can also cause disorientation and stranding (Kirschvink 2000). It works similar to the way man-made seismic activities cause acute embolism. 

Many papers are available for the necropsy of dead short-finned pilot whales in Sabu Raijua (Morimitsu et al. 1987; Jepson et al. 2003; Jepson et al. 2005; Cox et al. 2006; Yang et al. 2008). Contact me for the PDF version of the papers.

2.       Disorientation due to solar storm or geomagnetic storm 

The correlation between sunspots and sperm whale (Physeter macrocephalus) stranding events on the North Sea in 1619-2003 has been examined (Vanselow & Ricklefs 2005; Vanselow et al. 2009). The researchers concluded that the sperm whale stranding events happened during active sun spot years. 

Sunspot is a ‘dark’ region on the surface of the Sun. It actually is a ‘cooler’ region compared to neighbouring region. Excessive sunspots may cause solar storm which would disturb Earth’s geomagnetic and, in turn, might influence the cetacean’s navigation. 

 Photo of Aurora in Saskatoon, Saskatchewan @ Colin Chatfield  (30.09 - 1.10 2012) 

Here’s one example. Around 19 January 2012, some Coronal Mass Ejection took place on the surface of the Sun, creating a solar storm and beautiful auroras in the polar region three days later. On 23 January, 99 short-finned pilot whales (Globicephala macrorhynchus) stranded in Farewel Spitt, South Island of New Zealand. More than a third of the whales died. Suspecting the correlation between the two events, I contacted Klaus Vanselow last January. Vanselow examined the nT value, a value that describes the Sun’s influence on the Earth’s geomagnetic. Higher nT value means higher Sun’s activity and larger anomaly of Earth’s geomagnetic.  The nT value for 22 January was 102 nT for three hours, a very high value. Thus, Vanselow considered the high likelihood that the 23 January stranding was correlated to the Sun’s activities.

Going back to Sabu Raijua, without necropsy, it will be difficult for us to understand the main cause of the mass stranding event. However, notwithstanding possible pathological cause due to anthropogenic activities (e.g., naval activities, submarines, man-made sonars, etc), my attention drifts to the two natural events in the last few days:

·         Solar storm 30 September 2012

·         Earth quakes on 27, 29 and 30 September 2012

Solar storm

NOAA and Spaceweather.com reported a strong solar storm (G3 level) that hit the Earth in the evening of 30 September (GMT) up to the morning of 1 October (GMT). The storm was caused by a Coronal Mass Ejection on 27 September 2012. 

Earthquake

Three earthquakes occurred in eastern Indonesia for the last few days:

27 Sept 2012, 4.8 Richter, Naisano Dua, West Timor, 10:28:40 UTC (17:28:40 WIB)

29 Sept 2012, 4.8 Richter, northeast Palue, Sikka, Flores, 16:25:41 UTC (23:25:41 WIB)

30 Sept 2012, 4.4 Richter, NNW of Tobelo, North Sulawesi, 22:47:25 UTC (1 October 2012, 05:47:25 WIB)

I tend to suspect the two earthquakes in Timor and Flores (27 and 29 September) due to their relatively close distance to Sabu Island. My very rough guestimation is that the 27 September (82 km north of Kupang) had more correlation to the behaviours of the stranded pilot whales. If that particular earthquake 'startled' the whales, such that they made a rapid ascend and got decompression sickness because of it, the 30 Sept geomagnetic storm might worsen the situation by jamming their navigation system. Not a good thing, particularly if the whales were experiencing acute embolism.

Conclusion

Without conducting proper necropsy to the stranded whales, I tend to correlate the stranding event with the two earthquakes in East Nusa Tenggara (27 and 29 September) or with the recent solar storm (30 September – 1 Oktober). Nevertheless, I won’t discount possible disturbance due to man-made sonar or seismic activities. 

My recommendation for the Sabu stranding is thusly:

1.   Conduct a necropsy to the dead short-finned pilot whales in Sabu Raijua as soon as possible

2.   Obtain DNA sample for further analysis on the whale’s population

3.   Check if the Navy conducted sonar training at adjacent waters before or on 1 October 2012

My recommendation for long term management is as follows:

1. Increase the capacity of government officials and other stakeholders (particularly at Savu Sea) on the proper methods to rescue stranded marine mammals

2. Increase the capacity of related research institutes and vets, particularly in remote areas, to conduct necropsy and post-stranding forensic 

3. As I have announced before, at the moment the Marine Mammals Indonesia mailing list is establishing a database website to compile stranding events in the Archipelago from 1987 to date. When the website is already launched (expected mid October 2012), I hope the Ministry of Marine and Fisheries Affairs can use the website to improve the management of stranded marine mammals in the country

Reference:

Cox, T. M., Ragen, T. J., Read, A. J., Vos, E., Baird, R. W., Balcomb, K., Barlow, J., Caldwell, J., Cranford, T., Crum, L., D'Amico, A., D'Spain, G., Fernandez, A., Finneran, J., Gentry, R., Gerth, W., Gulland, F., Hildebrand, J., Houser, D., Hullar, T., Jepson, P. D., Ketten, D., MacLeod, C. D., Miller, P., Moore, S., Mountain, D. C., Palka, D., Ponganis, P., Rommel, S., Rowles, T., Taylor, B., Tyack, P., Wartzok, D., Gisiner, R., Mead, J. & Benner, L. 2006, 'Understanding the impact of anthropogenic sound on beaked whales', Journal of Cetacean Resource Management, vol. 7, no. 3, pp. 177-187.

Jepson, P. D., ARbelo, M., Deaville, R., Patterson, I. A. P., Castro, P., Baker, J. R., Degollada, E., Ross, H. M., Herraez, P., Pocknell, A. M., Rodriguez, F., Howie, F. E., Espinosa, A., Reid, R. J., Jaber, J. R., Martin, V., Cunningham, A. A. & Fernandez, A. 2003, 'Gas-bubble lesions in stranded cetaceans', Nature, vol. 425, no. 575-576.

Jepson, P. D., Deaville, R., Patterson, I. A. P., Pocknell, A. M., Ross, H. M., Baker, J. R., Howie, F. E., Reid, R. J., Colloff, A. & Cunningham, A. A. 2005, 'Acute and Chronic Gas Bubble Lesions in Cetaceans Stranded in the United Kingdom', Veterinary Pathology Online, vol. 42, no. 3, pp. 291-305.

Kirschvink, J. L. 2000, 'Earthquake Prediction by Animals: Evolution and Sensory Perception', Bulletin of the Seismological Society of America, vol. 90, no. 2, pp. 312-323.

Morimitsu, T., Nagai, T., Ide, M., Kawano, H., Naichuu, A., Koono, M. & Ishii, A. 1987, 'Mass stranding of Odontoceti caused by parasitogenic eighth cranial neuropathy', Journal of Wildlife Diseases, vol. 23, no. 4, pp. 586-590.

Vanselow, K. H. & Ricklefs, K. 2005, 'Are solar activity and sperm whale Physeter macrocephalus strandings around the North Sea related?', Journal of Sea Research, vol. 53, no. 4, pp. 319-327.

Vanselow, K. H., Ricklefs, K. & Colijn, F. 2009, 'Solar Driven Geomagnetic Anomalies and Sperm Whales (Physeter macrocephalus) Strandings Around the North Sea: An Analysis of Long Term Datasets', The Open Marine Biology Journal, vol. 3,  pp. 89-94.

Yang, W.-C., Chou, L.-S., Jepson, P. D., R.L. Brownell, J., Cowan, D., Chang, P.-H., Chiou, H.-I., Yao, C.-J., Yamada, T. K., Chiu, J.-T., Wang, P.-J. & Fernandez, A. 2008, 'Unusual cetacean mortality event in Taiwan, possibly linked to naval activities', Veterinary Record, vol. 162,  pp. 184-186.