Tetrapod Zoology

Like many ‘generalised’ carnivores, the Common or Harbour seal Phoca vitulina is a surprisingly adaptable predator, even if it is rather conservative in diet and choice of foraging habitat (e.g., Tollit et al. 1998). This photo, taken by Philip Kirkham, is part of a sequence in which a seal stalks, catches, and then dismembers and eats a duck (the duck is a Common eider Somateria mollissima). We all know that such pinnipeds as Leopard seals Hydrurga leptonyx and various sea lions and fur seals routinely catch and eat birds (Todd 1988), but it’s a bit surprising to see the small, normally piscivorous Common seal doing this.

The sequence of photos were featured in the Telegraph and can be seen here. I want to say more – to talk, for example, about the apparently increasing number of Common seals that are being killed by Great white sharks (Stewart & Yochem 1985), about facultative suction-feeding (Marshall & Dehnhardt 2005), and about the extraordinary sensitivity of Common seal whiskers (Dehnhardt et al. 1998, Zimmer 2001) – but I just don’t have the time, oh well. Thanks to Markus of Bestiarium for bringing these images to my attention. Back to work…

Refs – -

Dehnhardt, G., Mauck, B. & Bleckmann, H. 1998. Seal whiskers detect water movements. Nature 394, 235-236.

Marshall, C. D. & Dehnhardt, G. 2005. Behavioral performance of suction feeding in Harbor seals (Phoca vitulina). In 16th Biennial Conference on the Biology of Marine Mammals, Abstracts.

Stewart, B. M. & Yochem, P. K. 1985. Radio-tagged harbor seal, Phoca vitulina richardsi, eaten by white shark, Carcharodon carcharias, in the Southern California Bight. Californian Fish & Game 71, 113-114.

Todd, F. S. 1988. Weddell seals preys on Chinstrap penguin. The Condor 90, 249-250.

Tollit, D. J., Black, A. D., Thompson, P. M., Mackay, A., Corpe, H. M., Wilson, B., Van Parijs, S. M., Grellier, K. & Parlane, S. 1998. Variations in harbour seal Phoca vitulina diet and dive-depths in relation to foraging habitat. Journal of Zoology 244, 209-222.

Zimmer, C. 2001. By a whisker, harbor seals catch their prey. Science 293, 29-30.

Comments

#1 Dartian
March 6, 2009

You should send a link to this post to David Macdonald (of The Velvet Claw fame). Over the years, he hasn’t been too keen on including pinnipeds among Carnivora. Perhaps he needs to see more stuff like this to change his mind…

Incidentally, off the top of my head, I can think of at least one further report where bird predation by (non-Hydrurga) phocids was, if not proven, at least strongly implicated:

Lucas, Z. & McLaren, I.A. 1988. Apparent predation by grey seals, Halichoerus grypus, on seabirds around Sable Island, Nova Scotia. The Canadian Field-Naturalist 102, 675-678.
#2 Jerzy
March 6, 2009

I thought Grey and Common Seals would eat any seabird which is unwary or weak.

I remember from a trip to Faroes that Grey Seals several times tried to catch cormorants and eiders. Birds kept care not to sleep when a seal was swimming around. One Shag was a bit slow and had to take off quickly, and seal resurfaced when it was before.
#3 Will Baird
March 6, 2009

THE TIME HAS COME, MY FELLOW SYNAPSIDS!

The final battle is upon us! WE have unleashed the synapsid WMD[1]! The destruction has been vast and now it’s time to mop up the squawking, chirping, irritating diapsid survivors!

Rise up! Eat as many of them as you can! We MUST avenge the fall of so many of our friends and relatives at the claws, teeth, and beaks of the fowl diapsids!

RISE UP! RISE UP!

PS: Followup memo. No fraternizing with the enemy(2). Thank you.

1. aka Homo sapiens
2. Just in case… go here.
#4 neil
March 6, 2009

Thanks for ruining my day Darren.
#5 P Terry Hunt
March 6, 2009

A late 20th-century David Attenborough ducumentary set on the Falkland Islands, which for some reason is currently on BBC IPlayer here -
http://www.bbc.co.uk/iplayer/episode/b00779lz/Wildlife_on_Two_Rockies_and_Rollers/
– features a fur sea(?) preying on young cormorants(?) on land. These, mind you, are near-adult-sized ambulatory juveniles, not mere chicks. (Uncertainties because the footage is quite late in the programme and I don’t want to spend 40-plus minutes re-watching it.)
#6 P Terry Hunt
March 6, 2009

Darren, apologies for the extraneous ‘j’ in my e-mail address, spotted an instant after I clicked ‘post.’ Doh!
#7 P Terry Hunt
March 6, 2009

And “ducumentary” was obviously a freudian slip. Muphry’s Law strikes again!
#8 Jason J Brunet
March 6, 2009

I volunteer at the Seattle Aquarium and have this anecdote to offer: One day last year during a trainer talk at the harbor seal pool, a gull landed in the water and was promptly devoured by one of the male seals. It was witnessed by the public, but unfortunately I am unaware of any photos of the event.
#9 doug l
March 6, 2009

I’ve never seen a seal eat a bird but a few years ago while on a boat in Southeast Alaska I watched a Steller Sea Lion from a nearby sealion haulout prey on a small Harbor Seal. It took a few seconds to register what I’d just observed. A minor swish in the water, followed by a swirl of red colored water as an adult male Steller’s head arose with its mouth clamped on what I thought at first looked like a grapefruit, with a tinge of pink. The SeaLion rotated the object to gnaw on it using the side of its mouth which revealed that it was a defleshed skull and it became apparent what I’d just seen. Kind of grizzley at first but the mortal drama which had taken place mostly out of sight, just below the glassy water and amid all the abundant life in the nearby water left quite an impression.
#10 David Callahan
March 7, 2009

This is particularly interesting for me, having watched a Common Seal unsuccessfully trying to catch Teal, Mallard and various Gull species on the River Thames last autumn, right in front of the Millennium Dome. The seal gave up after about half an hour, after causing a fair amount of havoc, but I remember being a little surprised as there appears to be no shortage of eels and flounder, to judge by the prey seen in the bills of the Cormorants and Grey Herons I’ve seen feeding in that area.

Incidentally, a number of East London birders have reported a seal in the Limehouse area for a few years now, and it’s even been seen in the very lower reaches of the River Lea and in the dock at Limehouse Basin, apparently. It would seem that it doesn’t rely on commensality alone for its diet, and it might be the congregations of waterbirds and spawning fish in the now relatively clean Thames which keep it in Zone 2 (is this the most urban resident seal anywhere?).

Which reminds me, I must get around to reporting this to the London mammal recorder…
#11 Raymond Minton
March 7, 2009

Since I’ve seen a tiger in a zoo eating grass, a hippo on a nature documentary eating a wildebeest carcass, and (on this site) lions attacking elephants, I’d say I’m beyond being surprised by now.
#12 Brian Beatty
March 7, 2009

This is certainly more surprising than a leopard seal doing the same thing, but like in most cases, an animal’s diet is not as strict as paleontologists often want to think they are. It would be great if more people doing dietary reconstruction worked harder to compare details of individual animal diets (% composition, diversity) and study specimens with those specific dietary details known to form their analytical methods.
I’ve seen a pelican eat a pigeon (there’s even a video of a similar event on youtube now), but would say I was more surprised to see manatees eat rocks and invertebrates on multiple occasions.
Thanks for the pic, Darren!
#13 Graham King
March 7, 2009

Possibly loosely related to suction-feeding, I saw a seal at St Andrews Sea-Life Centre in Fife, Scotland repeating a peculiar action in its enclosure. It dived, blew bubbles, surfaced and blew a ‘raspberry’ (made a distinctive rasping sound) with its mouth held level exactly at the water-air interface; then dived again… and so on repeatedly. I am presuming it was just entertaining itself because it liked the sound/feel of doing so…?

Observing seals at my nearby North Queensferry Sea-Life Centre, I find it amazing how little bodily action they seem to require to keep moving, and how they circle underwater near the bottom of their enclosure inverted (ventral-uppermost, eyes-down) presumably scanning the pool-bottom for items of interest… is this inverted patrolling typical wild-feeding behaviour? (to seek crabs, fish etc on the sea-floor?) or a trait of captivity only?
#14 Graham King
March 7, 2009

I should give correct names and links.

Deep Sea World has Grey seals and Common/Harbour seals

St Andrews Aquarium has two Common/Harbour seals
named ‘Laurel’ and ‘Hardy’. The latter has ‘bubble-blowing’ listed as a hobby so I guess that it was him I saw…
#15 Darren Naish
March 8, 2009

Many thanks to all for neat and interesting comments.

Urban seals: we had a Harbour seal here in Southampton, about 2 km from my house and right in the middle of the city. The media christened it ‘Flipper’. However, it wasn’t really in an urban setting as the river – the tidal Itchen – has saltmarshes and mudflats.

Brian: I don’t think it’s fair to accuse palaeontologists specifically of making strict statements about diet. Surely everyone does this. We should note that, while animals may, on occasion, ‘disobey the rules’ (e.g., lions eat melons, elephants consume human carcasses, harbour seals eat ducks, dugongs eat tunicates), such instances are generally rare and account for a tiny proportion of diet.

Graham: in the wild, seals do frequently swim on their sides and upside-down.
#16 Alan
March 8, 2009

As far as the bubble blowing goes I recall seeing a BBC documentary of Common seals doing this in the wild. The best guess was that this was some kind of courtship display – Common seals from waht little I know do not go in for the sort of on-land fights that Fur seals do so they have these complicated underwater displays instead. Makes me wonder what else might be being missed from land based observations of seal behaviour..
#17 David C
March 9, 2009

In these events, does the seal definitely eat the entire duck/cormorant etc?

Based on what has been observed off S.Africa, could they merely be dismembering to gain access to stomach/gut contents (i.e. partially digested fish)?
#18 Darren Naish
March 9, 2009

For those interested in what David is discussing, the following papers refer to cases where Cape fur seals have been seen to kill gannets and to then feed predominantly on the viscera and stomach contents. If the fur seals were eating the stomach contents alone this might rank as a specialised form of ‘lethal kleptoparasitism’

Crawford, J. M. & Cooper, J. 1996. Cape fur seal Arctocephalys pusillus catch Cape gannet Morus capensis ashore at Malgas Island. Marine Ornithology 24, 53–54.

- . & Robinson, G. A. 1990. Impacts of seals on seabirds. In Report of the Subcommittee of the Sea Fisheries Advisory Committee appointed at the request ofthe Minister of Environment Affairs and of Water Affairs, to advise the Minister on scientific aspects of sealing. CapeTown: Sea Fisheries Research Institute, pp. 84–87.

Cooper, J. 1974. The predators of the Jackass penguin Spheniscus demersus. Bulletin of the British Ornithologists’ Club 94, 21–24.
#19 Dartian
March 9, 2009

‘Lethal kleptoparasitism’?. Yes, that could perhaps be a reason for pinnipeds to kill birds, at least under certain circumstances.

But getting at the stomach contents it not likely to be the motive in the case of the seal in Darren’s post. Eider ducks don’t eat fish – they mainly eat bivalves, particularly blue mussels Mytilus. And from a harbour seal’s point of view, a mouthful of half-digested mussels is probably not worth the bother.
#20 Glyn Young
March 9, 2009

Seals, and indeed killer whales, eating birds such as ducks and gulls is not uncommon and does seem to be increasing in UK waters. There is a school of thought that suggests it is coinciding with decreasing fish stocks making these mammals willing to tackle prey that they might have otherwise found less appertising (think of all those feathers!). There are now concerns about some eider populations in the UK as, particularly when moulting, they are pretty vulnerable to seals and whales. One persistent individual can easily wipe out some eider stocks.
#21 Jon H
March 9, 2009

Soon there will be photos posted of a seal skinning a human beachgoer.

I, for one, welcome our new pinniped overlords.
#22 Darren Naish
March 9, 2009

… I’d like to remind them that as a trusted Science-blogging personality I could be helpful in rounding up others to toil in their underwater cadaver-caves…
#23 Carmen Lang
August 5, 2009

I’m a UK resident happening to live in Huntingdon Cambridgeshire;
This morning after near three weeks of caring a young mallard duckling, the veterinarian clinic had adviced me after a check up to take the duck to the local river because such wild animals need to be reintroduced to their own and unfortunately, it was the best option I could do for him.He (Kismet) had immediately jumped into the water and swam for a family of ducks as soon as he was able. The young ones tried to drown him and in a panic we tried to call him back. Nonetheless, all we could do was lure him away, as he decided to swim to a cluster of lily pads close to the edge. My daughter had jumped to the river to try and cach the young kismet (and by then the water was only 1 metre deep) but in a moment a big surge of water flared up and kismet was instantly swallowed by a pair of jaws. Almost instantaneously he was gone without a trace.

Since this is the river Ouse, is it possible that it could be a seal? I have never heard of an animal *capable* of snatching another animal just one metres away from a full-sized human being.
#24 Dartian
August 6, 2009

Carmen: Judging by your description, it seems very unlikely that this mystery predator was a seal. A 1 metre-deep stretch of freshwater river isn’t a likely place for a seal to end up in. Seals usually don’t gulp down such relatively large prey in the manner that you described, either.

A large fish seems much more likely. A pike, perhaps, or a wels catfish. The latter are not native to the UK, but they’ve been introduced here and there, including Cambridgeshire AFAIK. Wels can get huge and they are known to catch prey as large as adult ducks, which they suck “into their mouths with a vortex motion” (according to this website).

My guess, then, is that poor Kismet ended up eaten by a big fish. Not an unusual fate for a duckling, alas.
#25 Dartian
August 6, 2009

Addendum to my previous post: as mentioned briefly in this account, carnivorous fish – pike, in this instance – are definitely a potential hazard to small, swimming birds in the UK (the phalaropes are about the same size as small ducklings).
#26 ML. Stephenson
April 15, 2010

This week, in the harbour at St. John, NB. Canada, I have seen Harbour seals leap straight up out of the water, like a ballet dancer. They look to be as high as five(5) feet, seen from the shore at a distance of one hundred (100) yards.
Also few years ago, I witnessed with a friend, the seals circling some water birds, and making noises seemingly like singing. This was in the Bay of Fundy, about one(100) yards off-shore.

I have tried to find out if seals leap into the air during mating, or fishing. No one seems to know. This practice has gone for three days, I think in, or near, a large school of fish.

No one here has ever noticed a singing sound from a group o seals either.

Can anyone confirm these peculiarities? Does anyone know why?

Thanks.