stoat reinvasions ofinshore islands has been seriously under-estimated.
Lack of knowledge and research likely led to the claim that stoats could only swim 1.5km. Stoats (predators) pose a much larger risk if they are able to expand their reach to other islands that potentially host endangered species.
all islands of the New Zealand archipelago\3–5 km offshore should be treated as at risk ofinvasion by stoats, (2) the ‘‘safe’’ zone for importantconservation islands inshore has been drasticallyunderestimated, and (3) the assumption that suchislands do not need the continued surveillance
The study concludes that many islands previously considered secure are actually within stoat swimming range which ultimately means that conservation strategies must be updated, as outdated assumptions could leave endangered species vulnerable to reinvasion.
A fit and active wild stoat free tochoose its own time, motivation and swimming speedmight swim much further, especially given the addedbuoyancy of salt water.
This reinforces that the experimental results represent minimum capability, not maximum. Wild stoats, especially in ocean conditions, could travel significantly farther, expanding the realistic threat radius around offshore islands.
Fore-leg strokes averagedabout 220–300/min at all current speeds (Table 2), andwere much longer and deeper than those of the hindlegs (Figs. 3 and 4).
This fore-legged stroke largely explains the stoats' ability to sustain long-distance swimming, which contradicts the belief that small size limits their swimming potential.
Three of the males swam strongly for more than anhour, and one of the females for nearly 2 h (Table 1);two males and one female swam for more than half anhour.
This result shows that stoats have far greater endurance than conservation authorities originally assumed, especially since these were captive animals under stress. If a stoat can swim nearly 2 km in controlled conditions, wild stoats aided by tides or debris could easily surpass distances once believed impossible, meaning many offshore islands are more vulnerable to reinvasion than previously thought.
Weassumed that a stoat which could maintain a constantposition against the current at a given speed couldswim forward at that speed in still water.
This shows how researchers had to build a controlled method to estimate real swimming ability because no reliable data existed before. The fact that such basic measurements were missing explains why earlier claims underestimated how far stoats could actually swim.
More than 70 species of terrestrial vertebratesare recovering or likely to recover as a result of theseeradications (Towns et al. 2013), but the problem ofdetecting early reinvasions remains acute (Elliott et al.2010).
Even after major conservation successes, reinvasion remains a constant threat, especially if stoats can reach islands previously considered safe. This highlights how predator mobility directly affects long‑term conservation outcomes.
On land, marked individualstoats have been recorded dispersing[20 km within afew weeks of independence (King and McMillan1982), and swimming across fast rivers withouthesitation
Stoats' abilities to disperse on land were already pretty great, but their willingness to swim across strong rivers shows that water is not a barrier for them. This challenges the assumption that offshore islands are protected simply because they are separated by water