Rare sightings and seals by Fiona Mathews
This article was written by former Mammal Society Chair, Fiona Mathews. It has appeared in the magazine British Wildlife in June 2021. At the time of posting (19 June 2021) Wally the Walrus has moved from Tenby to France and Spain and was most recently seen off the coast of the Isles of Scilly.
Fiona Mathews is Professor of Environmental Biology at the University of Sussex.
Twitter: @FionaMathews
The arrival of Wally the walrus in Pembrokeshire has to rank as one of the most sensational wildlife events of the year. After a brief sojourn in Ireland, he was spotted on rocks near Broad Haven South beach in Pembrokeshire, and has since taken up residence on the RNLI slipway at Tenby, becoming a media celebrity in the process. This is not necessarily a good thing. Wally disappeared for a few days after clearly being disturbed by tourists who were trying to approach closely using jet-skis, paddleboards and drones. Ironically, this came shortly after the launch of the ‘Give Seals Space’ campaign launched by the Seal Alliance to encourage responsible wildlife watching. The timeliness of that message was brought home in late March, when a juvenile common seal Phoca vitulina that had become a regular attraction near London’s Hammersmith Bridge had to be euthanised following a dog attack. Every year there are incidents of disturbance being caused by over-eager and ill-informed members of the public.
The UK is a critical location for pinnipeds (seals). We have around 40% of the world’s population of grey seals Halichoerus grypus (around 120,000 individuals >1 year old) (Special Committee on Seals, 2017), and globally these animals are around 4 times rarer than African elephants Loxadonta africana. Around 88% of our grey seals breed in Scotland, with the main concentrations occurring in the Outer Hebrides and in Orkney. UK populations have increased over the past 25 years (Thomas et al. 2019), but growth appears to be levelling off in all areas except the central and southern North Sea. Harbour (or common) seals have a broader global geographical distribution, and approximately 30% of the European population (around 42,000 animals of the North Atlantic subspecies P. v. vitulina) are found in the UK. It was previously thought that the UK population was in decline, but recent analyses show that overall it is of similar size to that in 1990, albeit with different patterns prevailing in different regions: the south-east (English) populations have increased, despite temporary falls because of phocine distemper virus outbreaks in 1998 and 2002; the north-east populations (East Scotland, Moray Firth, North Coast and Orkney, and Shetland) have declined; and the north‐west populations (West Scotland, Western Isles, and South‐West Scotland) have remained stable or increased (Thompson 2019).
Back to Wally the walrus, there is little doubt that he is a lost lone animal. There are precious few records of walruses Obodenus rosmarus in the UK. Since 2000, there have been just two sightings, both of which were in Orkney: one in 2013 and the second in 2018 (Crawley et al. 2020). Walruses once extended into southern waters, which suggests that they are probably able to tolerate warmer climates, but they are generally restricted to the Arctic seas presumably because of prey availability. There are occasional southern sightings in other locations, such as in the Gulf of St Lawrence in Canada, and the Netherlands Coast.
Walruses are now the sole member of the genus Odebenus, and also the sole member of the family Odobenidae. But about 5-10 million years ago, they were the most abundant and diverse pinnipends in the Pacific Ocean. Their closest living relatives are the fur seals. They feed principally on bivalve molluscs such as clams, cockles and mussels, and will also take invertebrates from the seabed, including shrimps, crabs, polychaete worms, octopuses and sea cucumbers, which they locate using highly sensitive vibrissae. Their tusks are not used for digging out clams as previously thought (though they do have a remarkable ability to shoot large amounts of water out of their mouths to pressure-jet prey out of sediments). Instead, the tusks are largely social ornaments, like the antlers of deer, which, when needed, are used in earnest as fighting weapons. Tusks can also serve as an extra limb to help the animal haul out of the water, to break breathing holes in ice, and as the most unlikely of headrests.
Wally can be identified as a juvenile on the basis of the relatively short length of his tusks. After weaning, young walruses will remain with their mothers and other adult females for 2-4 years, after which time the males will break away, usually forming their own small groups in winter or joining with larger bull herds in the summer. Walruses are renowned for being gregarious, usually forming tight groups when hauled out and also staying in groups at sea. Occasional observations of solitary individuals are rare, and these are usually adult males. It is therefore particularly unfortunate that Wally is a long way from home and separated from his social group.
While it is easy to verify that Wally is indeed a walrus, and his location is well-documented, the same is unfortunately not true of many other unusual mammal observations. This is a pressing problem as we seek to understand the responses of wildlife to climate change — could the recent findings of Geoffroy’s bat (Myotis emarginatus) or Kuhl’s pipistrelle (Pipistrellus kuhlii) in the south of England be sentinels of northward range shifts? Even for species normally resident in the UK, the charting of changes in distribution, such as the spread of red deer (Cervus elaphus) in Wales or the contraction of the red squirrel (Sciurus vulgaris) in England and Wales, is vital for assessing changes in conservation status. In addition, we need to keep a vigilant watch for the arrival of invasive non-native species such as the raccoon (Procyon lotor).
The exercise of drawing together the new Atlas of the Mammals of Great Britain and Northern Ireland (Crawley et al. 2020) revealed that many unsubstantiated records had made it through the normal verification and record-checking process, necessitating a mammoth data-cleaning exercise. My own excitement at discovering 50 or so records of greater mouse-eared bat (Myotis myotis) quickly evaporated when further checking revealed that almost all of them were mistakes. We are therefore setting up a Rare and Scarce Records Committee, following the excellent example from the British Trust for Ornithology. In addition, we are updating the outputs of our Ecobat web tool to provide users with local and European distribution maps and the system will flag unusual bat species records, something increasingly important with the growing use of automated classifiers for bat sound files. These initiatives will enable the Mammal Society to provide more regular updates on unusual sightings and to investigate before the trail goes cold. If you would like to help, please do get in touch with us (info@themammalsociety.org). Of course, if you do make an unusual sighting, do remember to submit it! This is easy via either the Mammal Mapper phone app or iRecord. Please include photographic evidence if possible.
Crawley, D., Coomber, F., Kubasiewicz, L., Harrower, C., Evans, P., Waggitt, J., Smith, B. and Matthews, F. eds., 2020. Atlas of the mammals of Great Britain and Northern Ireland. Pelagic Publishing Ltd.
Special Committee on Seals. (2017). Scientific advice on matters related to the management of seal populations: 2017. http://www.smru.st‐andrews.ac.uk/files/2018/01/SCOS‐2017.pdf
Thomas, L., Russell, D.J., Duck, C.D., Morris, C.D., Lonergan, M., Empacher, F., Thompson, D. and Harwood, J., 2019. Modelling the population size and dynamics of the British grey seal. Aquatic Conservation: Marine and Freshwater Ecosystems, 29, pp.6-23.
Thompson, D., Duck, C.D., Morris, C.D. and Russell, D.J., 2019. The status of harbour seals (Phoca vitulina) in the UK. Aquatic Conservation: Marine and Freshwater Ecosystems, 29, pp.40-60.