Ommatophoca rossii
Enormous eyes, a voice like a siren, and a species we have barely managed to observe at all.
Four kinds of seal live in the pack ice around Antarctica. The Ross seal is the smallest of them and, by a long way, the least seen. It is short, stout and thick-necked, with a pug face, a strongly domed forehead and a stubby muzzle that looks nothing like the long snout of a grey seal or an elephant seal. The back is dark chocolate-brown fading into a silvery-white belly, and many of them carry bold dark streaks running down the throat and chest.
Hardly any Ross seals have ever been caught and measured, so everything we know about their size rests on a handful of animals. What that handful shows is that the females are the bigger sex. A female runs about two to two and a half metres long. Males are shorter, usually under two metres. Biologists call that reverse dimorphism, and it is odd, because in nearly every other seal it is the male who is the giant.
Weight tells the same story with one wrinkle worth knowing about. Females are typically the heavier sex, but the single heaviest Ross seal ever put on a scale, at two hundred and sixteen kilograms, happened to be a male. When you have only ever weighed a few animals, one unusually large individual can sit at the top of the list without changing what is normal.
The neck is thick and loose, and the seal can pull its head back into it like a hand disappearing up a sleeve. A startled Ross seal looks like it has no neck at all, just a pair of enormous eyes set in a barrel.
The Ross seal's other name is the singing seal, and it earns it. It makes complicated twittering and siren-like sounds, up on the ice and down in the water, and they carry a long way through the pack. The underwater siren can be two completely separate notes at once, stacked on top of each other and pulsed in the same rhythm. Try humming two different notes at the same time and you will see the problem.
The strangest part is how it does this. A Ross seal sings with its mouth shut and lets out no air at all. The sound is made and recycled inside the animal, so singing costs it nothing. It can call over and over again underwater without ever surfacing for a breath.
Nobody knows what the songs are for. There are two obvious guesses. The calls might help animals that live alone find each other across an enormous, almost empty field of ice. Or they might help them stay out of each other's way. Ross seals are nearly always found on their own, so either job would be a useful one, and nobody has shown which is right.
Satellite tags answered a question that watching the seals never could. For months at a stretch, Ross seals are not on the ice at all. They are far out in the open Southern Ocean, often near the Antarctic Polar Front, hunting in deep water nowhere near a floe.
What they are hunting is squid and fish, and the useful clue is where those fish live. Look at what is in a Ross seal's stomach, then check the chemical traces left in its body from months of eating, and both point to the twilight zone. That is the layer of ocean between roughly two hundred and a thousand metres down, where the last of the sunlight gives out and a great many of the animals make their own light instead.
Hunting down there takes enormous eyes, and the Ross seal has them: seven centimetres across, each one about the size of a tennis ball. Its face is a direct readout of its job. It also explains how an animal filed under Antarctic pack ice seal manages to spend so much of its life nowhere near ice.
That is not a figure of speech, and it is not a dodge. The 2026 IUCN assessment says it outright: there are no reliable population estimates for this species, and working out whether the numbers are rising or falling is, at the moment, not achievable.
The guesses that do exist are all over the place. Surveys through the last century produced world totals running from twenty thousand animals at the low end to two hundred and twenty thousand at the high end, and the assessment treats both ends as highly speculative.
The figure you will see quoted most often is about a hundred and thirty thousand. It comes from seals spotted from ships and aircraft decades ago, and it arrived with no measure at all of how wrong it might be. Using it to spot a change is like guessing the size of a football crowd from one photograph of one stand.
The best survey anyone has managed, in the pack ice off East Antarctica, landed on about fifty thousand seals. Then it added the honest part: the real answer could be as low as twenty thousand or as high as two hundred and twenty seven thousand. That is not a small wobble. It is the difference between a rare animal and a fairly common one, and the survey cannot tell them apart.
None of this is for want of trying. Ross seals live alone, spread thin, inside the thickest jammed-up pack ice ringing an entire continent. Getting to one means an icebreaker or a helicopter. Their pupping areas are effectively unreachable, which knocks out the trick used on almost every other seal on Earth: fly over the breeding beaches and count the babies.
This animal has had a name since 1841, and the list of things nobody has ever watched it do is still long. No one has ever seen Ross seals mate. It is assumed to happen in the water, mostly because it does not happen anywhere anyone can see. For decades everybody assumed one male keeps a group of females, the way most seals do, until genetic work published in 2011 found no sign of that and hinted the opposite, that they pair off one to one.
What is known has an odd, patchy texture to it. Pups are born in November, most of them in the first half of the month, and are thought to be weaned after about a month. A female coming into the pack ice to give birth hauls out and stays put for the best part of a week, slipping back into the water only for an hour or two at a time.
After that it is mostly shrugs. In summer, most of them are lying out on the ice around midday. Moulting is thought to happen in January, when they seem to stop eating. They are thought to be old enough to breed somewhere between three and six, and they live at least twenty years. Even how often a female has a pup is a blank. Almost every sentence anyone writes about this animal's life carries a "thought to be" inside it, which is a strange thing to be true of a large mammal in the twenty-first century.
What happens to them as the sea ice goes is genuinely argued over. One side says they will suffer, because they need solid pack ice at particular points in the year. The other says they may be among the least affected of all the Antarctic seals, precisely because they do their hunting far away from the ice anyway.
A habitat modelling study in 2021 came down on unclear, and probably different from place to place. Less ice could shorten the swim between the nursery and the feeding grounds, which saves a seal energy. That gain could be cancelled out by prey moving elsewhere, by the loss of floes to rest on, and by more competition from big predators like southern elephant seals moving in.
There is also a newer worry. Highly pathogenic bird flu reached the Antarctic continent, confirmed in 2024, and it can jump from birds to mammals and then between mammals. Ross seals spend most of the year alone, but they do come together to breed and to moult, and coming together is exactly what a contagious disease needs.
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