Weather conditions have not been cold enough to send slugs into hibernation, meaning the creatures have remained active in months when they are normally asleep.
The creatures remain active when temperatures remain above 5C, and with little snow or frost, they have simply kept going through the cold months.
The gastropods could lay up to 200 eggs per cubic metre, and it’s estimated that the average UK garden could be home to up to 20,000 slugs.
It may not be good news for gardeners, however, with slugs considered pests. There are also fears of invasive foreign slugs seeing a massive increase in the UK.
December 2015 was the warmest since records began in 1910, with temperatures around 7.9C (46F), making it feel more like April or May - for slugs as well as people.