Lions have no particular breeding season, and often synchronize breeding, especially after a pride takeover, raising the cubs communally. Birth peaks have been observed in Kruger (February – April) and Serengeti (March – July) National Parks related to seasonal weather patterns and prey availability , .
Male lions become sexually mature at around 26 months old , but unlikely to breed before the age of four or five, primarily due to a lack of opportunity until they are large enough at around this age to take over a pride and therefore its breeding rights. At Phinda reserve in South Africa introduced males sired cubs at 27 months. The mean age of first conception in Kruger National Park is 48 months although 29% sired cubs at 40 months . Breeding by some males was delayed until 54 – 60 months. Males as old as 16 can produce viable sperm, but reproduction probably ceases after their pride tenure is lost.
Females at Phinda conceived for the first time at 32 – 33 months  with most lionesses having given birth by the time they are four years of age . Females can breed until they are c. 15-years old, but reproduction usually starts to decline at 11 years. A lioness in the Kgalagadi Transfrontier Park gave birth at 19 years old .
Onset of oestrus is in response to within-pride mechanisms such as oestrus in pridemates as well as loss of cubs from infanticide at pride takeovers ,  - . Lionesses are polyoestrus, oestrus lasting 4 – 7 days with intervals between periods of a few days up to more than a year (average 55.4 days). They have a post-partum oestrus but do not conceive if the litter survives. If the litter is lost a new one may be produced within four months .
When a litter is raised to maturity the mean litter interval is 601.5 ±119.8 days at Phinda ; In Serengeti NP the mean was 20 months (range 11 – 25)  when a litter was raised to maturity and a range of 4 – 6 months if it lost.
Courtship may be initiated by either member of the pair who remain close during the oestrus period. The female usually invites copulation by lordosis. There is little competition amongst pride males during mating. Instead of fighting to be the first to mate a female in oestrus, a male will follow her around very closely at the first signs of oestrus onset. Other males keep their distance unless there is a clear size difference, in which case a larger male may fight a smaller one. This works because females have a long oestrus period and copulate many times during that period. Males may lose interest before the end of an oestrus period, giving patient males a chance. Also, due to the common synchrony of reproduction there is often more than one female in heat at any one time. A lioness mates up to 100 times per day with an average interval of 17 minutes (range 4 – 148), each mating lasting for c. 21 seconds (range 8 – 68) , ,  – .
During the periods between copulation the pair may lie down next to each other or walk a short distance. The male may gently stroke the female with his tongue on the shoulder, neck or back to initiate copulation. Towards the end of copulation the male may gently bite the back of her neck. During copulation the female may purr loudly.
Male cats have spines on their penis to cause slight trauma to the vagina upon withdrawal. The resulting pain triggers ovulation . It may also explain why females bare their teeth at males during mating. The penis is also mobile and can be pointed backwards or moved from side to side for scent spraying. Conception occurs on the 4th day of oestrus with a conception rate per cycle of 38%. The level of nutrition influences both fertility and litter size .
Gestation & Cubbing
Gestation is between 100 – 120 days. Just prior to cubbing the female will move away from the pride and give birth in a well hidden lair. The typical number of cubs in a litter is three (range one – six). The postpartum litter size is virtually the same to litter size in utero with the sex ratio at parity , ,  – , . Cubs weigh c. 1.65 kg at birth gaining c. 106g per day in the first four weeks of life .
Communal Care of Cubs
The female will only rejoin the pride with her cubs if the cubs already established in the pride are not more than 3 months old. The reason for this is that all lactating females suckle cubs indiscriminately, showing only limited favouritism to their own offspring. Therefore young cubs would suffer in competition against cubs over 3 months old. This collaborative behaviour probably stems from the close genetic relatedness among a pride’s females (each sharing c. one seventh of their genes with pride mates ), each lion is enhancing her own genes’ success by helping raise her sister’s offspring. Cubs suckle regularly for the first 6 – 7 months, the frequency declining thereafter. Cubs remain with their mother for 21 – 24 months up to 30 months , ,  – .
Cub mortality is high; in Kruger c. 50% died , a similar figure was given for Nairobi National Park . In Etosha National Park and Mashatu the figure was lower at 40%  –  whilst a figure of 67% was given for the Serengeti . There are many reasons for mortality in cubs; first, teething is painful and weakens the cub so that many die during this time. Disease is an important factor in cub mortality, as is abandonment; mothers often get absorbed by some activity and forget for a while that she has cubs. A male taking over a pride may kill cubs under a year. Cubs are predated upon by other carnivores as well as buffalo. Finally, cubs are at the bottom of the food chain; a mother will let her cub starve if she’s hungry and will not slow her pace for a cub older than five – seven months, which once left behind has little chance of survival. As many as 80% of cubs will die before the age of two years.
|Day 1||Cubs are 1 - 2kg at birth, they are blind and helpless.|
|Day 3 - 11||Their eyes open but vision is little more than a blur for another week.|
|Day 10 - 15||Cub starts to walk.|
|Day 21 - 30||The milk teeth erupt; the canines come first with the back teeth a few weeks later.|
|Day 25 - 30||The cubs are able to run|
|Month 1 - 2||Cubs come out of hiding and are capable of the full repertoire of lion calls except roaring.|
|Month 2 -3||Able to keep up with the pride and start to observe prey movements. Weaning starts.|
|Month 6 - 10||
The cubs are weaned but remain dependent on their mother until month 16, or even later.
|Month 9 - 12||Eruption of permanent teeth begins but may take some months to complete the process. Cubs start to take part in hunts.|
|Month 12 - 24||Cubs make their first kills, usually on small or injured animals.|
|Month 24 - 27||
Both males and females become sexually mature.
|Year 2 - 3||Young males are pushed out of the pride. Young females unable to stand up to pride adults may also be forced to leave|
|Year 3 - 4||Reach adult size|
|Year 4||Females have given birth to their first surviving litter|
|Year 4 - 5||Males take over a pride tenure|
|Year 7||Weight peaks, mane reaches fullest extent|
|Year 10||Males ousted from their pride quickly die but may survive until c. 14 - 16 years if part of a strong coalition|
|Year 11||Female breeding starts to reduce|
|Year 10 - 15||Females die but may survive until c. 15 - 18 years|