Islanders reported seeing the Coypu, which looks like a large rat, near Rozel earlier in the week.
The rodent is an invasive, non-native species.
It's not currently clear how the Coypu got into the island.
The animal was culled and eradicated in the UK in the 1980's because they were damaging flood defences and crops.
Jersey Government's Natural Environment team are urging islanders not to approach the rodent if they see it but to instead report it on 441674 or the duty officer on 441617 out of office hours.

Serious bacterial infection found in unvaccinated dog
Ban for Guernsey supporter cautioned over Muratti trouble
Coronation Park extension opens, but with no pump track... yet
100 Jersey fields listed as Minister says PFAS testing shows no contamination
Water bills to rise 6.9% from 2027
Bulls away games no longer streamed on YouTube
Carer avoids jail for historic sex offences against child
Haut du Mont trial: Island Energy ‘wouldn’t spend the money’ on vital safety training, court hears