Over which time period s did the squirrel population decrease?

The squirrel population typically experiences fluctuations due to various factors, such as food availability, predation, and environmental conditions. Specific time periods of population decrease can vary by region and species, but significant declines have been noted during harsh winters or after habitat destruction. Additionally, disease outbreaks can also contribute to population decreases. For precise data, it's essential to refer to local wildlife studies or reports.