Not all slugs are bad – introducing the Leopard slug ( Limax maximus )

Leopard Slug
Michal Maňas, CC BY 2.5, via Wikimedia Commons

Not all slugs are bad – introducing the Leopard slug (Limax maximus)

More than a few British gardeners have some choice words when you mention slugs and snails and they have a myriad of ways to try and stop them from munching on their flowers and vegetables. From slug pellets to copper strips, beer traps to nightly collection and dispatch, the war on our slimy molluscs has raged for centuries. Not surprising really when the average garden may contain up to 20,000 slugs!

However, there is a hero in the slug world – the Leopard Slug. Ok so they don’t wear a cape like your traditional ‘super’ hero, but they are beneficial to the garden and gardeners. Unlike other slugs, the Leopard slug feeds on detritus and other slugs, reaching speeds of up to 15cm per minute when in pursuit of other slugs!

Despite the name, Limax maximus is not our largest slug and on average reaches about 15cm. It is a member of the family Limacidae, the keeled slugs. First described England by Martin Lister in 1678 (though it had been noted 12 years earlier by physician Christopher Merett) it is native to Europe and the Mediterranean and is a common slug found in diverse habitats such as woodlands, gardens and basements. Mainly nocturnal, they can be seen in daylight when it’s raining, warm and overcast. Their diet can be quite varied and includes detritus, algae, dying plant parts, carrion, other slugs and their eggs. The leopard slugs have also been seen to reduce the number of other slug species within the garden and therefore are beneficial to the gardener.

Mating between leopard slugs is a sight to behold, they twit their bodies together and mate in mid-air whilst suspended from a mucous string attached to a plant or another surface. Once entwined both slugs push out enormous penises from openings on the side of their heads and as the slugs are hermaphrodites they fertilise each other’s eggs whilst in this mating position. After mating up-to 200 eggs are laid which develop into tiny white slugs. Some of the sperm may be stored to use another time or may end up being eaten by the slug.

We have quite a healthy colony of leopard slugs in our garden, mainly living in the compost bins, they are fascinating animals and interesting to study, especially as they have been shown to exhibit associative learning and is capable of aversion learning. For instance, the slug shows aversion to food that has deficiencies in its nutrition content, that may be toxic or food that has been poisoned. More specifically these slugs can exhibit taste aversion which occurs after ingesting food that causes nausea or vomiting.

So if you come across leopard slugs in your garden or allotment, try to welcome these slug ‘super heroes’ and not take the normal gardeners actions……..

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