Hedgehog surveys in Jersey have suggested that the population has dropped by more than a third in the last decade.
Preservationists think the hot summer and mild autumn has had a hard impact on the mammals.
The warm conditions have also impacted bugs and insects, taking away a large source of food for hedgehogs.
The lack of sightings and collections of hedgehogs is concerning to those who look after them.
Dru Burdon, from the Jersey Hedgehog Preservation Group, said: "We honestly don't know if they're fit and healthy and out there because it's nice and mild out there and it's raining so there's plenty of wild food.
"It's just such a funny November. We've just never had such a mild November before."
Whilst islanders may initially believe a lack of sightings means the hedgehog population are thriving in the wild, it actually means the opposite.
Gillian Morgan, from the Jersey Hedgehog Preservation Group said: "A lack of reports leads us to believe there is indeed a decline in Jersey hedgehogs.
"Yes, the weather has had an impact. Climate change has an impact but other factors have an impact as well of course."
Conservationists are doing all they can to stop the decline. A survey is currently underway to get a better snapshot of the situation in Jersey. All islanders who happen to spot a hedgehog are being encouraged to report it to the preservation group by the end of this month.
How can you help a hedgehog?
Make sure hedgehogs can access your garden with a 'Hedgehog Highway’ a 5” x 5”square gap in the bottom of fences or walls
Create a log pile that will offer shelter and natural food.
Build a Hedgehog Home
Move piles of rubbish to a new site on the day you are burning it and check it carefully before setting light to it, lighting from only one side so that there’s an escape route should you have missed anything.
Check areas carefully before mowing or strimming.
Ensure netting is kept at a height that allows hedgehogs to pass safely under it.
Check compost heaps carefully before digging the fork in.
Stop using pesticides and poisons.
Cover drains or deep holes.
Ensure there is an easy route out of ponds and pools.
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