The population of interest and the sample are:
Population of interest: All lions in the wild.
Sample: The 55 lions that were caught and measured by the researchers.
Characteristics used to estimate population: Weight, sex, running speed, and leg size.
The researchers are not interested in the specific 55 lions they caught, but rather want to use their characteristics to draw inferences about the entire population of lions in the wild.
This is a classic example of using a sample to estimate population parameters.