The sexual behavior of Weddell seals is a very private matter – unintentionally, at least as far as science is concerned. It takes place underwater, away from the curious view of biologists. To my knowledge, only one copulation has been observed. Of all times, it was during an underwater television taping session by some University of Minnesota biologists.

There is now a permanent record of the event! Unfortunately, if there was any precopulatory behavior it was not viewed or taped. This event took place on December 7, 1969. Based on circumstantial evidence, this is near the end of the breeding season. Microscopic examination of male seals' testes provide indirect evidence that most spermatogenesis occurs from mid–September to the end of December.

Although copulation and conception occur mainly in December, when the seals are most concentrated in and near the pupping areas, development of the fertilized egg is delayed until mid–January or mid–February. At this time, the egg implants in the uterine wall and development goes forth to result in a birth in October.

A prelude to birth and copulation is the establishment by a few bulls of territories below the ice. To my knowledge, this is the only documented case of a marine mammal holding a territory in the water. Other ice–breeding seals, as well as some whales, may occupy similar territories, but the necessary detailed studies have not been done.