Slug Lifespan: How Long Do Slugs Live?

Slug is a common term used for any terrestrial gastropod mollusk without a shell or containing only a small or reduced internal shell. They belong to the same class, Gastropoda, as snails and are found nearly everywhere in the world. You’ll likely find one underneath every decayed log, leaf pile, mulch mound, or compost pile you inspect, no matter where you live. And even if you don’t see them, the tell-tale mucus track glistening in the daylight lets you know that they are there.

Slugs are secretive, solitary, and silent invertebrates with nocturnal lives that go on primarily unnoticed by those around them. Here, we look at a slug’s lifespan and the conditions and variables that help determine just how long a slug lives.

Life Expectancy of Slugs

The short answer is an average of between 12-18 months. In natural outdoor settings, most land-dwelling slugs live up to about a year, while their aquatic counterparts can live up to five years. The more accurate answer depends on several variables.

Slugs found in warmer climates have shorter lifespans than those in cooler climates. Those slugs that are fortunate enough to have a comprehensive and bountiful food source will always be able to outlive those that don’t live near adequate food and shelter resources. Slugs are vulnerable to parasites, diseases, and extreme weather conditions that negatively impact their natural food sources and, consequently, their lifespan.

Additionally, natural predators like birds, reptiles, and humans can dramatically change the slug’s lifespan. However, when laid in the right place under the right conditions, the slug’s eggs can remain dormant for years. When conditions become right, the eggs will hatch and begin their life journey.

Features of a Slug

Common slug colors generally range from brown to dark gray. Others are brightly colored, and some feature speckled bodies as well. Slugs are classified as invertebrates and consist of a head, foot, and sole, with two pairs of retractable tentacles, or feelers, projecting from their head. The upper pair of feelers senses light and contains eyespots at the ends. The lower pair is the slug’s sense of smell.

Slugs use an organ called a radula to scrape food particles away from their surface and digest them. The radula is a rough, raspy, tongue-like organ that contains toothy protrusions that grind food. Although slugs possess a respiratory opening on one side of the mantle, the saddle-shaped part of their body behind the head, they can absorb oxygen directly from the atmosphere. Depending on the species and surrounding environment, slugs normally range between one and eight inches long.

What a Slug Eats

Slugs and snails are scavengers, and as such, they are not picky about what they ingest. Their main food source is dead or decaying organic matter, but they will also tackle fresh, leafy greens, fruits, flowers, and vegetables. Some slugs feed on fungi, lichens, and plants, including petunias, chrysanthemums, daisies, lilies, daffodils, and more.

Some slugs eat other slugs, snails, and earthworms, while others will eat mushrooms and slime molds. It’s also common for slugs to ingest small stones, gravel, or anything that provides them with their necessary supply of calcium carbonate.

Slug Habitat

You have to look hard to find a habitat where a slug doesn’t exist. They live everywhere, including forests, grasslands, and even deserts. We’ve all seen them, or evidence of them, around our home gardens and damp exterior locations. Slugs are most active at night and in the early morning hours. In daylight, they are prone to hiding under wood, mulch, stones, leaves, and soil.

Many species of slugs are environment-specific and cannot live long outside of their normal habitat conditions. Slugs live both beneath ground and above ground. Some may burrow underground for protection from predators and extreme weather, while others are happy living out their lives in above-ground logs and tree trunks. Warmer climates generally produce larger slugs, while cooler climates produce smaller slugs.

Slug Behavior

Slugs are generally solitary creatures known to be aggressive with one another. When they do gather together, it is likely to try to remain cool in warm weather. Many species are nocturnal, with the heaviest activity occurring after rainfall.

Slugs spend their downtime in dark, damp areas that are conducive to retaining body moisture. They move by contracting the muscles on the underside of their body, creating a wave motion that propels them forward. Their mucus is excreted from the foot, allowing them to move across the landscape friction-free.

Slugs communicate with one another by releasing pheromones. Pheromones are released by the special organs located on either side of a slug’s head. Other slugs receive these signals through their tentacles. Slugs use pheromones for many reasons, including to mark their territories and find mates of the same species.

Additional Slug Facts

• Slugs evolved from snails. Interestingly, most slugs are still born with protective shells but discard them once they grow older and mature. For this reason, snails can retreat into their shell for protection while slugs must retreat underground or in some structure for that same protection.
• Slugs produce two types of mucus. The thin mucus is for grip and is how slugs recognize those of the same species for mating. It also helps with hunting. The thicker mucus coats their body, keeping them moist and protecting them from predators that try to pick them up. The mucus has an unpleasant taste and is thick enough to incapacitate and trap certain predators.
• Slugs are hermaphrodites, possessing both male and female organs. They mate by exchanging sperm and laying egg clusters in favorable conditions.
• Slugs cannot regenerate or regrow lost or damaged body parts.