The truth of the matter is that leopards “become extremely cautious around larger predators such as lions and tigers, and prefer to retreat to cover or the safe haven of a tree rather than face a direct encounter”. That, I believe, satisfactorily answers the question in the title. They don’t want to fight lions because they’re going to come off worse. The lion is substantially larger and we all know what a fierce and aggressive animal it can be. The majority of people believe a lion can beat a tiger in a fight.
In some parts of its distribution such as in Sri Lanka, the leopard is the largest carnivore present and therefore they don’t have to worry about being attacked by superior predators. However, in most places where this large wild cat lives, they do so in conjunction with a range of larger and smaller predators and scavengers.
Some of these predators become food for the leopard while others prey on the leopard or their cubs and they steal their kills. Hyenas and lions, for example, steal kills from leopards when the opportunity presents itself. Leopards sometimes kill the cubs of other carnivores such as lions, cheetahs and hyenas.
But in the Serengeti lion’s chase leopards whenever they see them and the leopards invariably climb a tree to escape or retreat to a kopje (a small hill in a generally flat area).
One man living in India, Arjan Singh, said that all three of the leopards that he raised had “an instinctive dread of tigers”. They would flee when they came across the scent of a tiger. Leopards have an instinctive aversion to the larger wild cat predators. When this man was walking in the forest with a tame female leopard, they saw a tigress cross the road. He observed a distinct change in his leopard’s behaviour. He said that “her demeanour changed entirely. Her high-spirited desire to lead the way evaporated. She went into a crouch, and her whole body lengthened as she slunk towards the big cat’s trail and disappeared into the bushes.”
Okay, the man was describing a leopard encountering a tiger but the same rules apply. Leopards become cautious and evasive around predators bigger than themselves for the obvious purpose of avoiding injury which would lead to a slow death or death itself in an unequal fight.
Both leopards and lions (and tigers) feed on the same prey species but it is said that competition between them for the species is slight. In general, the leopard feeds on a wider range of animals than the lion or tiger, often the young of the larger prey species. This is in contrast to the lion which generally preys upon the adults of the same species.