Red triangle slug fact sheet | Field of Mars EEC

What are red triangle slugs?

Red triangle slugs are large native Australian land slugs. They are Australia’s largest native land slug and can grow up to 14 centimetres long.

Their scientific name is Triboniophorus graeffei. They are named after the red triangle on their back. This triangle surrounds their breathing pore, called a pneumostome.

Red triangle slugs are molluscs. They belong to the gastropod group, which includes snails and slugs. They are also called leaf-veined slugs because the pattern on their back can look like the veins of a leaf.

A red triangle slug.

Red triangle slugs have one pair of tentacles and a red triangle around their breathing pore.

Where do red triangle slugs live?

Red triangle slugs are found along the east coast of Australia, including New South Wales and Queensland. They live in moist habitats such as forests, woodlands, heath and gardens.

During dry weather, they shelter in damp places under bark, logs, rocks and leaf litter. After rain, they may be seen crawling on tree trunks, rocks, paths or walls.

At Field of Mars Reserve, shaded bushland, leaf litter, rocks, logs and smooth-barked eucalypts provide habitat for many small animals, including native slugs.

Red triangle slugs live in moist forests, woodlands, heath and gardens.

What do red triangle slugs eat?

Red triangle slugs graze mainly on microscopic algae growing on smooth-barked eucalypts, rocks and other damp surfaces. Their mouth has a rough, tongue-like structure called a radula, which scrapes food from surfaces.

As they feed, they can leave scalloped trails that look like small chain marks on tree bark. If a red triangle slug enters a house, it may also graze on bathroom mould.

Red triangle slug feeding trails can look like scalloped chain marks on smooth bark.

What is the life cycle of a red triangle slug?

Like many slugs, red triangle slugs have both male and female reproductive parts. When two slugs mate, they may curl around each other and exchange sperm.

Red triangle slugs lay eggs in damp, sheltered places such as under leaf litter or fallen logs. These places help protect the eggs from drying out.

Young red triangle slugs look different from adults. Juveniles do not have the bright red triangle and red border seen on adults. Instead, they may have a grey-outlined triangle and dark stripes along their back.

Red triangle slugs may curl around each other when mating.

What adaptations do red triangle slugs have to help them survive?

Red triangle slugs have several adaptations that help them survive in moist bushland habitats. Their soft body helps them squeeze into sheltered spaces under bark, rocks and logs. Their mucus helps them move across rough surfaces and reduces water loss.

Their red triangle marks the position of the breathing pore. This pore allows the slug to breathe air while moving through damp habitats.

Red triangle slugs also have an unusual defence. When threatened, they can produce a very sticky mucus from their back. Research has shown that this mucus can glue a predator, such as a frog, to a surface long enough for the slug to escape.

Red triangle slugs produce mucus for movement and defence.

Why are red triangle slugs important?

Red triangle slugs are part of the bushland food web. They graze mainly on microscopic algae and may become food for animals such as frogs, reptiles, birds and other predators.

Their feeding trails are a sign of animal activity in the bush. Even when the slug is hidden, its scalloped marks on smooth bark can show that it has been feeding nearby.

Red triangle slugs also remind us that damp microhabitats are important. Leaf litter, bark, logs, rocks and shaded places help many small animals survive.

Juvenile red triangle slugs are part of damp bushland food webs from an early stage.

How can you help red triangle slugs?

You can help red triangle slugs by protecting moist habitat. Leave leaf litter, bark, rocks and logs in bushland where it is safe to do so. These places provide shelter for slugs and many other invertebrates.

Avoid using pesticides or chemicals unnecessarily in gardens, especially near damp habitat and native plants.

If you find a red triangle slug, observe it gently and do not handle it. Its body is soft and can be easily damaged. If one is found indoors, ask an adult to carefully move it to a damp, shaded place outside.

Red triangle slugs are soft-bodied animals and should be observed gently without handling.

Related fact sheets

More invertebrate fact sheets

• Invertebrate fact sheets – Explore insects, spiders, molluscs and other small animals found in Sydney and NSW.
• Gastropods fact sheet – Learn about the mollusc group that includes slugs, snails, limpets and sea slugs.
• Snail fact sheet – Compare another gastropod that also needs moist habitats and a muscular foot.
• Millipede fact sheet – Learn about another damp-habitat invertebrate found in leaf litter, soil and under logs.
• Pill bugs fact sheet – Compare small decomposers that also shelter in damp leaf litter, logs and soil.

Habitats and ecosystems

• Field of Mars Reserve fact sheet – Explore the local bushland habitats that support native plants, invertebrates and other animals.
• Eucalypt forest fact sheet – Learn about forest habitats with smooth-barked trees, leaf litter, rocks, logs and sheltered microhabitats.
• Tree habitats fact sheet – Explore how trunks, bark and branches provide habitat for living things.
• Leaf litter habitats fact sheet – Learn how fallen leaves create damp shelter for many small animals.

• Rock and log habitats fact sheet – Find out how logs, rocks and hidden spaces provide shelter for small animals.

Animals that share this habitat

• Common eastern froglet fact sheet – Compare a small frog that lives around damp leaf litter, wet grass and shallow water.
• Striped marsh frog fact sheet – Learn about another animal active in damp habitats after rain.

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