The increase in the snake's mass after consuming a mouse can be attributed to several factors. When a snake eats, it takes in the mass of the mouse itself, which includes its body tissues, fat, and any water content.
However, it's important to note that not all of the mass will be retained in the snake’s body. The snake will lose some mass through waste products (such as undigested materials and metabolic waste) after digestion. The increase in mass that the snake experiences will be approximately equal to the mass of the mouse minus the mass lost through digestion and excretion.
In a simplified scenario, if the snake consumes a mouse weighing X grams, the immediate increase in the snake's mass will be less than X grams due to these losses. Overall, the increase in the snake's mass can be considered roughly equal to the mouse's mass minus any waste produced during digestion and metabolic processes.