Increasing rat numbers in cities are linked to climate warming, urbanization and human population

Urban rats are notorious invasive pests that thrive in cities by exploiting the resources accompanying high human population density. Identifying long-term trends in rat numbers and how they are shaped by environmental changes is critical for understanding their ecology, and projecting future vulnerabilities and mitigation needs. Here, we use trend analyses of public complaint and inspection data in 16 cities around the world to estimate trends in commensal rat populations. Eleven of 16 cities (69%) had significant increasing trends in rat numbers, including Washington D.C., New York, and Amsterdam. Just three cities experienced declines. Cities experiencing greater temperature increases over time saw larger increases in rat numbers. Cities with more dense human populations and more urbanization also saw larger increases in rats. Warming temperatures and more people living in cities may be expanding the seasonal activity periods and food resource availability for urban rats. Cities will have to integrate the biological impacts of these variables into any future management strategies.

城市鼠类是臭名昭著的入侵性有害生物，它们依托高密度人类群体伴生的资源在城市环境中繁盛繁衍。探明鼠类种群数量的长期变化趋势及其受环境变化的调控机制，对于理解其生态学特征、预测未来种群脆弱性及制定防控需求至关重要。本研究通过对全球16座城市的公众投诉与巡查数据开展趋势分析，估算了共生鼠类（commensal rat）的种群变化趋势。在16座城市中，11座（占比69%）的鼠类种群数量呈现显著上升趋势，其中包括华盛顿哥伦比亚特区、纽约市与阿姆斯特丹；仅有3座城市出现种群数量下降。随时间推移气温升幅更高的城市，其鼠类种群数量的增幅更为显著；人类人口密度更高、城市化水平更强的城市，鼠类种群数量的增幅同样更大。气温升高与城市居住人口的增加，可能会延长城市鼠类的季节性活动周期，并提升其可获取的食物资源量。各城市在制定未来的鼠类防控管理策略时，必须将这些变量带来的生物学影响纳入考量范畴。