Wednesday 30 December 2020

Sperm whale stranding at Withernsea


A mass stranding of ten Sperm Whales was reported on Christmas Eve in the stretch of coast between Withernsea and Tunstall. I've never seen a whale stranding before and, although a very sad event, it allows for a rare occasion to experience these large mammals up close. Last night, finding that some of the whales were still on the beach I decided to pay them a visit. 

It was a clear morning, with large shower clouds, but it fortunately kept dry for us. Low tide was at about 10 am, ideal to walk on this stretch of coast, as watching from the crumbly cliffs after the last rains is not advisable. After parking by Withernsea's Memorial Gardens, we walked along the north promenade, and upon reaching the end of it, two of the whales became visible in the distance. There were a few people about, several wearing masks, and it was easy to keep social distance.

Four of the stranded sperm whales, with Tunstall caravan park in the distance.

A short brisk walk and we reached the first whale. The first impression, after taking in the immense size of it, was the fact that the penis was everted, making it very obvious that this, like the other individuals, were all male. We walked around the whale, taking in its odd anatomy. Sadly, it's jaw had been cut off and taken away by a looter. This, according to the team carrying out the necropsy, makes their job harder, in addition to being an illegal act to take possession to any part of a cetacean.

It's a boy!

Liquefying mud, the reason why walking on top of the cliffs at this time of the year is not a good idea.
Several crows feeding on the beach, I wonder they were eating bits of blubber, which we found scattered on the strandline.

Whale 2.
Indentations in the fluke of one of the whales.
Each of the whales had unique bits missing from their flukes, which may aid in individual identification to researchers.
Scars showing healed propeller injuries on the back of one of the whales.



Whale number 3. A team from the RSPCA, the Cetacean Strandings Investigation Programme, based at the Institute of Zoology in London and the British Divers Marine Life Rescue were in attendance, taking measurements and samples as part of a necropsy. An cut on the back of the whales, allows for pressure to be released from the bodies, as the gut decomposes, releasing gas. The cut also revealed the thick layer of blubber (fat) and the very dark muscle, rich in myoglobin. Surprisingly, the whales didn't smell much unless you were directly downwind.
Individual number 4. The upper mandible shows the indentations where the teeth in the jaw fit, and the decomposed tongue.
Small teeth are present in this individual's upper mandible, breaking the gum, which is unusual in sperm whales.
Some of the guts of the whales were spilled on the beach.
The first steps of the necropsy of whale number 4, the furthest from Withernsea.
A stranded dogfish
After looking at all the whales and having a chat with some of the researchers in charge of the necropsies, we returned to town, looking for whale number 5, which was just off the RNLI station. This was the only specimen that was complete with its jaw. I counted 23 pairs of teeth. This individual appeared in a more advanced decomposition stage than the others and will be removed from the beach tomorrow.

The last whale we saw was by the RNLI rescue station.
This was the only individual with the jaw intact. 23 pairs of teeth were visible
Some onlookers inspecting the whale.

Some Sperm whale facts

Physeter macrocephalus, Linnaeus, 1758

The largest toothed whale, a deep-water squid-eating specialist. Sperm whales are cosmopolitan and found at deep waters all around the world. The population of sperm whales is quite mixed, with little genetic structure around the world.

The head is massive and block-shaped (the 'macrocephalus' of the species name meaning massive head) and can make up to a third of the body length of a bull. It contains a large fibrous sac filled with a mix of oils and waxes, the spermaceti, which is used in echolocation and may also aid with the animal buoyancy. The spermaceti and was one of the valued products of their hunt as it was used to make high quality lubricants. 


Views of the heads of two of the whales.

The sperm whale is a strong contender to the deepest and longest animal diver. Bulls can dive down over 2,000 m deep to hunt on the sea floor, although dives are often shallower, to about 400 m. Dives take from half an hour to a record of just over 2 hours long.

Sperm whales have a single, S-shaped blow hole, the left one. The left nasal passages are used to make sounds. Their blow spray is low and distinctly asymmetrical, pointing left and forward.

They have the largest brain of any animal. In contrast, their eyes are relatively small and conical, and can be retracted and protruded from the eye cavity.

The eye of one of the sperm whales

Strongly sexually dimorphic, males can be up to 3 times as heavy as females, with average weight at maturity 44 tonnes for males (max of 80!) and length of 16 m, whereas females weigh 13 tonnes and measure 11 m. Bulls reach sexual maturity at 18-20 years old and can live up to 70 years old. Males are able to dive deeper and carry on growing until they reach 50 years old. Sexes are segregated in their geographical distribution, adult males live in higher latitude cold waters, while females stay in warm, tropical seas in family groups year round. Immature males leave their natal groups at 10-15 years, when they join 'bachelor groups' and migrate to northern waters. As they age they become less social, and mature bulls become solitary, only visiting female groups in tropical waters to mate.

Adult females, their calves, and immature offspring form strongly social groups called 'mixed groups', likely to be structured as elephant's herds into maternal lines. Young may be cared for all females in the group. This 'babysitting' allows mothers to feed, as dives can take a long time, when the calves can be exposed to predators. In the North Atlantic the Canaries and Azores are important breeding grounds. 

Communication is by series of clicks or 'codas', which may be individual specific. Males also 'clang'. Echolocation involves the emission of powerful clicks aiding in the localisation of prey such as medium to large size squid in the deep sea, but also sharks and rays from the sea floor.

History of Sperm Whale strandings

Sperm whales have stranded in the north sea for centuries, the earliest record in 1560, and this species have the best recorded stranding history of any cetacean. The most famous historical stranding is that of a 17 m long young male Sperm Whale in 1825 just in this very same stretch of coast. This is the account of the stranding by James Alderson, the surgeon from Hull who carried out the dissection of the animal:

[the sperm whale] was seen on the after noon of Thursday the 28th of April, drifting up from the southward with the ebb tide, off Tunstall in Holderness , and in the course of the afternoon was landed low in the tide . At the ensuing flood it was floated higher up on the beach , where it was left during the early part of the ebb. It may seem extraordinary, but it is no less true, that it was not generally known in Hull to be on shore until the Tuesday following.

The carcass was claimed by the then Lord of Holderness Sir Thomas Constable, its skeleton cleaned and eventually mounted on the grounds of Burton Constable. This skeleton was then unique in the world and was visited and described in minute detail by Thomas Beale in his monograph 'The Natural History of the Sperm Whale', from which Herman Melville borrowed widely for his 'Moby Dick' novel. The remains of this sperm whale skeleton (missing the jaw) now resides at Burton Constable.

Remains of the Burton Constable whale skeleton, which I visited in 2014. The wrought iron structures presumably being those used to mount the skeleton on the grounds of the hall.

Why did they strand, is it do do with human activities?

The southern basin of the North Sea is a hotspot for sperm whale stranding. All sperm whale strandings in the North Sea are of males, most of bachelor herds formed by immature individuals, and are strongly concentrated between November and March. Sperm whales are deep sea animals that don't belong to the shallow North Sea (depth is less than 40 m). They visit the deep waters of the Norwegian Sea, where they find plentiful squid (Gonatus fabricii), which can be easy to catch in their spawning grounds. In the late autumn and winter they migrate south through the Faeroe-Shetland channel. It is during this migration that some some bachelor herds may take a wrong turn and move into the southern basin of the North Sea, where the sea is progressively shallower, with sandy, gradually changing depths where their echolocation is not as efficient as in deeper seas and where they are highly likely to end beached. They are such massive animals that rescue is not an easy option and then, even if it were possible, the whales would be unlikely to find their way back to safer waters.

Despite the long history of strandings in the North Sea, their frequency across years changes markedly. There appear to have been an increase since the 70s. There was a large number of strandings in 1996 and 1997, then a long period with few strandings, and a large number again in 2016. This could be related to the long-term recovery of the sperm whale population after whaling stopped (in the 80s), but there is no good population estimates. In early 2016, 30 Sperm whales were stranded in five countries around the southern North Sea. Researchers took advantage of this to collect as much data as possible from the whales, and try to ascertain the reasons behind mass stranding events. The whales were all immature males 10-16 years old, in good nutritional status. Their stomachs contained thousands of beaks of Gonatus squid, which is not found in the north sea, confirming that they had travelled recently from Arctic waters. The whales examination did not reveal any illness that could explain the stranding. Parasites, trauma, water temperature changes, storms and earthquakes (potentially affecting echolocation) were also ruled out. Geomagnetic disturbances caused by solar storms have been proposed to be involved as they may interfere with whale navigation. The relatively inexperienced bachelor herds may more easily succumb to these dangers. A higher risk of young, inexperienced males to die in 'natural traps' has also been proposed to explain the strong male bias found in fossils mammoths. As sperm whales, mammoths have a matrilinear society with solitary bulls and bachelor groups of young males.

More information

Credland, A. G. Moby Dick, Hull and East Yorkshire. Great Circle 11, 44–54 (1989).

Harris, S & D.W. Yalden (2008) Mammals of the British Isles. Handbook 4th Edition. The Mammal Society.

Alderson, J. (1827). An account of a whale of the spermaceti tribe, cast on shore on the Yorkshire coast, on the 28th of April, 1825. Transactions of the Cambridge Philosophical Society, 1827, 253-266.


MacDonald, D. (ed.) 2002. The New Encyclopaedia of Mammals. Oxford University Press.

Pečnerová, P. et al. Genome-Based Sexing Provides Clues about Behavior and Social Structure in the Woolly Mammoth. Curr. Biol. 27, 3505–3510.e3 (2017).

Vanselow, K. H., Jacobsen, S., Hall, C. & Garthe, S. Solar storms may trigger sperm whale strandings: explanation approaches for multiple strandings in the North Sea in 2016Int. J. Astrobiology 17, 336–344 (2018).

Sunday 27 December 2020

Urban birding at Hull: Beverley and Barmston drain in December

The morning started sunny and surprisingly after the storm there was little wind. I took an impromptu walk to the closest stretch of Beverley and Barmston drain to home, between Abbey Way and Fountain Road. I always like to watch the drain from the pedestrian bridge at Abbey Way. I could see two Little Grebes on the water, a species that is not found in many places in Hull. Some moorhens and mallards were about. A charm of Goldfinches fed on the plane trees.

I moved onto the next stretch of drain. A small bird called from a birch. It was a lone Lesser Redpoll. Another rare sighting in Hull, only my second record this year. After repeatedly calling, it settled to feed. As Goldfinches do, it deftly used its feet to hold a birch catkins onto the branch where it was perching to feed on it. 




Lesser Redpoll.

I checked the playing fields by the cycle track. Three Song Thrushes were feeding on the edge of it. Something spooked the gulls, but I failed to see what it was.

I stood by the bridge on Fountain Road. The drain was quite full and flowing like a river. A completely different feel from my last visit, when the surface was covered on duckweed. A Cormorant gulped a fish. I heard a Jackdaw, it flew onto a chimney. What a great morning on the drain.  

A crow had a chicken breast bone and was cleaning it. It was able to carry it away when challenged by the other crow.

A pony in the stables by Fountain Road.
Jackdaw.

The view of the last stretch of drain from Fountain Road.
Cormorant and Moorhen.
This year, the drain has really been a bonus. Great for dragonflies, with Hairy Dragonflies and Willow Emeralds and 11 species seen; fantastic for birds, and also including an Otter sighting. Today I added three species to the year bird list for the Sculcoates km square stretch of the drain, totalling 50 species.

Tuesday 15 December 2020

Wild swan chase

A family of Bewick's Swans, two adults and two young, have been roosting at North Cave Wetlands since the 4th of December, with a large flock of Whooper Swans. Bewick's swans migrate from their breeding grounds in the Northern Siberian tundra to winter in the UK and other NW European countries. They are an amber listed species, with a strong decline in the UK wintering population since the 1990s, now amounting to about 4000 individuals. Although I had visited the roost a week ago, I missed the Bewick's, which would be a lifer for me. Today, it was an early start to try and catch up with my last wild UK swan species as the swans usually depart before sunrise to their feeding areas.

I got to the reserve at 7:15, still pitch dark. The Bewick's seem to have favoured to roost at Island Lake in the last few days, so I headed that way, walking fast towards turret hide. When I got to the hide, Fozzy was there, waiting for the light to be good enough to distinguish the swans. After some squinting it became apparent that the Bewick's were at the far end of the lake, their size noticeably smaller. There were 43 Whoopers, arranged in discrete family groups. The only Mute Swan present served as a good comparison of the three UK swan species. At some point two Greylags on an island were near the Bewick's, and it was amazing to realise that both species are of similar size.

Record shot of the Bewick family.

The Whooper families were starting to become itchy, with much head bobbing and vocalising as they prepared to take off. Their arrangement reminded me of a busy airport runway, with planes in a queue ready to leave. We watched as two flocks left Reedbed Lake, and soon they were followed by the first departing Whoopers from Island Lake. Turret Hide offered a high vantage point, allowing from great views of the spectacle that was the departure of each group of swans. As they flapped their wings and paddled with their feet on the water, each swan family left parallel trails on the water, then the swans taking off and gaining hight as they flew near the hide. The increasing light made the Bewick's a bit easier to distinguish, but conditions for photography were still borderline before dawn. It was a clear day with little wind, ideal flight conditions for swans, so not very surprising that they left quite early, at 7:43, flying just in front of the hide, before turning west.

Three swan species on Island Lake, the Bewick's family on the left, Whoopers on the centre and mute Swan towards the back right.
My last poor photo of the Bewick's before they left the roost.
The last group of Whooper's to depart.
Redwing.
A view from Crosslands hide.

I did a circular walk around the reserve. Many Redwing and a flock of Siskin, a wisp of five Snipe over and half a dozen Curlew on North Field were the highlights. I wanted to see the swans feeding, and hopefully try to see the Bewick's in better light, so it was time for a road trip. 

The swans had been seen feeding during the day in stubbles around the Bursea area, about 5 km from North Cave Wetlands. After driving around the narrow lanes in the area, not finding any swans, I decided to head back via Tollingham, and on a field, by the long shadow of a wind turbine, I spotted the large swan flock. The entrance to the turbine's service road made for a convenient parking spot, out of the way of lane traffic, and distant enough from the swans that they wouldn't be disturbed. I lowered my window and used the car as a hide. Some of the swans eyed me, but they carried on doing what they were doing. A slow scan revealed that there were no Bewick's amongst the 76 Whoopers visible. I spent some time watching the swans, there were occasional squabbles, but they were mostly relaxed, loafing or feeding, occasionally vocalising. Black-headed Gulls, Common Gulls and Starlings had joined them in a flooded part of the stubbles. A Meadow Pipit flew to a hedgerow and a Skylark chirped overhead. 

View of some of the herd of Whoopers.

The herd is clearly made of separate families, the young, recognised by their brownish feathers, keeping close to their parents. 
Feeding and resting Whoopers.

Then, four swans flew low towards me, the Bewick's! They carried on, East, and I managed a few flight shots.

Oncoming Bewick's
Fly over


Whooper resting with one leg up.

After about 20 minutes, the Bewick's family returned, and landed towards the left of the field. Unfortunately they were mostly obscured, I only managed to photograph their heads over the stubble. Still, I was quite pleased to catch up with them, a lifer for the end of the year is not bad!

Bewick's landing.
Record shot of two of the Bewick's.