How far can rodents swim?
As a guide: Brown rats can swim better than black rats which can swim better than house mice. Mice, however, are high-risk stowaway invaders.
At 50m all rodents can easily swim to an island, and will do so frequently.
At 500m black rat will invade but the frequency of incursions may be low.
At 500m brown rat could, in many circumstances, be expected to reach the island every year
Simple ways to protect seabirds from invasive non-native predators and disease while travelling to seabird islands
Ffyrdd syml o amddiffyn adar môr rhag ysglyfaethwyr estron ymledol a chlefydau wrth deithio i ynysoedd adar môr