“Leopard cubs are born after a gestation period of about 96 days, although zoo records suggest that gestation can take anywhere from 90 to 105 days.”
The information is a direct quote from the premier book on the wild cat species, Wild Cats of the World by Mel Sunquist and Fiona Sunquist. They are referring to the work of two authors: H. Hemmer who wrote Gestation period and postnatal development in felids, which was published in 1979. The second work referred to is Reproduction of captive wild carnivores. It was written by S.W.J. Seager and C.N. Demorest and published in 1978 in Zoo and wild animal medicine.
A bit more about leopard reproduction
Normally the leopard’s litter size varies between one to three cubs; although there are records of six cub litters, while the norm is two cubs. It may be the case that spotted leopards have larger litter sizes (2.09 cubs) compared to melanistic leopards (1.7 cubs). Melanistic leopards are black leopards aka black panthers.
The association between male and female leopard during mating is brief. A male and female were not seen together for more than one day in the Kalahari Desert, while in the Kruger National Park the average length of association between male and female was two days with a variation between one and four days. One scientist, Bailey, reported that “most courtship associations were apparently unsuccessful”. Only 2/13 or 15%, “suspected matings resulted in the birth of cubs”.
In a captive situation observing eight female leopards, another scientist, Eaton, estimated that the probability of conception was 0.65 (R.L. Eaton, Reproductive biology of the leopard, published in 1977).
Dunbar Brander reported that in India leopards bred at all times. He said that he came across more cubs in April that at any other time (Dunbar Brander – Wild animals in Central India, published in 1923).
It seems that births take place during the season when prey is more abundant or easier to catch. For instance in Ruhuna National Park, Sri Lanka, most births were believed to take place during the dry season as prey was easier to catch at water holes (M de Silva and B.V.R. Jayarate – Aspects of population ecology of the leopard (Panthera pardus) in Tuhuna National Park, Sri Lanka, 1994).
In Kruger National Park, five out of size litters were born in the wet season (Nov-Dec), the peak time for impala births (T.N. Bailey in The African Leopard published in 1993).