Scientists say they know little about leopard seals because the seals live alone in the Antarctic pack ice. Leopard seals live mostly on and around the pack ice of Antarctica, in Antarctic and sub-Antarctic waters, and they usually live alone. Leopard seal population size is difficult to determine, and one source estimates a population of at least 35,000 leopard seals but says the estimate is probably low, as of November 2026. An estimate from 2000 put leopard seals at 200,000 to 400,000, as of November 2026, and low densities of solitary animals over vast areas are difficult to estimate.

Aerial seal surveys use helicopters with paired observers searching the same strip of ice independently, and in one survey so few leopard seals were sighted that it was a major obstacle in developing population estimates. As of November 2026, scientists in 1999 and 2000 had recorded underwater sound at 101 sites in the Davis Sea, Eastern Antarctica, between 4 December and 10 January to count leopard seals by their calls, and the recordings captured a total of 38,270 leopard seal calls. As of November 2026, an acoustic survey of the same Davis Sea region and time estimated 5,926 leopard seals across 19,820 square kilometres, about 0.31 seals per square kilometre, while a visual survey estimated only 0.006 leopard seals per square kilometre. The 2013 study authors state that visual surveys alone are likely to vastly underestimate the population of leopard seals.

Sources disagree on basic life facts, and they disagree on how long a leopard seal pregnancy lasts: 9 months in one, about 10 months in another. Lifespan figures differ across sources: up to 30 years recorded in the wild in one, 12 to 26 years in another. Sources also differ on when leopard seals mature: females at 3 to 7 years and males at 2 to 6 years in one, males at 3 years and females at 2 in another.

As of November 2026, an older record put the longest leopard seal dive at about 15 minutes, before the 25-minute dive recorded in 2022, which was 1,256 metres deep.

As of November 2026, scientists had tagged 22 leopard seals off the Western Antarctic Peninsula to follow their dives and travels. In that study, as of November 2026, the tagged seals dived on average to about 30 metres and for about three minutes. As of November 2026, among the tagged seals, the farthest distance travelled ranged from 46 km to just over 1,669 km, and tagged leopard seals ranged from South Georgia Island to Adelaide Island. As of November 2026, two tagged adult female leopard seals spent two weeks on ice in the middle of the ocean.

Even the birthplace is argued, and, as of November 2026, a review of birth and pup records found that 84.2 percent of birth records and 57.4 percent of pup records are from outside Antarctica, while the same review contradicts the long-standing idea that leopard seals only give birth on Antarctic pack ice.

Leopard seals mate in December and early January, and they are believed to mate in the water, while leopard seal births in the records occur between September and December. A mother leopard seal gives birth to a single pup, and a newborn pup weighs about 30 kilograms or more, and it is nursed for about four weeks, after which, once weaned, leopard seal pups start hunting krill.

Words to know

• estimate: a best guess
• acoustic: using sound
• contradicts: says the opposite
• weaned: done nursing