You should first draw a diagram to show all the process occur in water cycle Evaporation: The water from the rivers rises in the form of vapours and reaches up to the cloudes. Precipitation: The water stored inside clouds and pour water to the earth in the form of rainfall.
Then this water reaches inside soil which help plants to grow and develop and also help in achieveing nutrients and minerals which enhance their respiration process.
After this water loss due to transpiration in plants vapours again and from the rivers also to continue this nature cycle known as Water Cycle.
If want a direct answer it would be the decrease in mice, but if you want to get technical the decrease in grain spills caused mice to leave so that would be the indirect cause
