a leopard can't/doesn't change its spots

Examples from literature

Although the patterns on the fur of tigers and leopards are very different, both serve the same purpose – to make it harder for their prey to see them. 
Safari guides can help you find Africa’s Big Five: lion, leopard, water buffalo, rhinoceros, and elephant. 
This tortoise lives in the savannas of Africa – just like real leopards. 

leopard | American Dictionary

leopard
noun[ C ]
us/ˈlep·ərd/
a large, wild cat that has yellow fur with black spots and that lives in Africa and south Asia

Examples of leopard

leopard
Long-time residents recall lions and leopards here and elephants not much further north.
The final reference to" leopards not changing their spots" shows just how far this explanation has moved onto the terrain of" race" thinking itself.
Were its creators men, showing how women's reproductive powers depended quite literally upon male courage and skill, their assuming of leopard nature?
At either side of her lies a leopard, face turned to us like hers.
Despite their wide distribution, little is known of the ecology or behaviour of leopard cats in the wild, especially in human-modified landscapes.
Based on scats from captured leopard cats in this study, an average diameter of 1 cm was used as a guide.
Was it women, showing how woman's power drives the hunt, nourishing leopard children on the magic of meat transformed to milk?
The vervet's problem domain is the predator, the categories of which are: raptor, leopard, and snake, to which it produces three different calls.
Trap locations were selected based on the presence of tracks and scats (faeces) as well as sightings of leopard cats during preliminary nocturnal surveys.
The camel with a leopard on his back (photograph 30) from the central portal of the facade is a good example.
Men (leopards) hunt, bring home the dead bull and other noble prey.
They include lions, tigers, leopards, jaguars and pumas, but all but two animals were at large for only one day.
From the
Hansard archive