Here's why:
* ATP is the energy currency of cells. It's constantly being produced and used by living organisms to power their functions.
* Upon death, cellular processes immediately cease. This includes the production of ATP. However, the ATP that was already present in the cells will begin to degrade.
* The rate of ATP degradation varies. The specific conditions (temperature, environment, etc.) can affect how quickly ATP breaks down. But in general, the sooner after death, the higher the concentration of ATP will be.
Therefore, a recently deceased organism will have a relatively high amount of ATP compared to an organism that has been dead for a longer period of time.
