What adaptation allows rats to thrive in urban environments?

The ability of rats to thrive in urban environments is heavily linked to their great adaptability to human waste. Urban areas produce a significant amount of waste, providing a consistent and plentiful food source for rats. They have evolved to exploit this resource, feeding on discarded food and organic materials found in garbage, compost, and landfills. This adaptability to consume a wide variety of food items, especially human waste, allows them to flourish in settings where traditional food sources may be scarce.

While the other options present interesting adaptations, they do not contribute as significantly to urban survival as the ability to make use of human waste. For instance, digging deep burrows can be an advantage in natural environments but is less necessary in cities where rats often find shelter in buildings and sewers. Highly developed social structures may help with survival and reproduction but are not unique to urban settings nor pivotal in relation to urban adaptability. Similarly, while being nocturnal can aid in avoiding human detection, it does not directly facilitate the ability to thrive on human waste as an urban survival strategy does. This makes the ability to utilize human waste the key adaptation for rats in urban environments.