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Red triangle slugs are Australia’s largest native land slug, reaching sizes up to 14 centimetres in length!
They are named after the distinctive red triangle on their back, which contains their breathing pore (called a pneumostome). The scientific name for red triangle slugs is Triboniophorus graeffei.
Red triangle slugs belong to a group of molluscs called gastropods - gastro meaning stomach, and pod meaning foot. This group includes all snails and slugs.
Red triangle slugs are a type of leaf-vein slug, meaning they have a vein running down their back which resembles the veins of leaves.
As a native slug, red triangle slugs also have only one pair of tentacles on their head, whilst introduced slug species have two pairs.
Red triangle slugs come in a variety of colours including white, off-white, yellow, grey, beige, pink, red and olive green, although all varieties share the same distinctive red triangle. Scientists are currently trying to determine whether these colour variations are in fact different species of red triangle slugs.
Red triangle slugs are found along the east coast of Australia. The natural habitat of red triangle slugs include forests, woodlands and heath where they can be found living in moist areas such as under bark, rocks and logs. During wet weather they can be found crawling on top of rocks, along tree trunks and branches.
Red triangle slugs are also commonly found in urban areas and are frequently sighted in gardens and bathrooms!
Red triangle slugs bury themselves in leaf litter during the day and at night come out to feed.
Red triangle slugs graze on moss and microscopic algae which grows on the surfaces of smooth-barked gum trees and rocks. As they graze they leave behind scalloped tracks (small arc-shaped markings) on the bark.
If a red triangle slug makes its way into a house it has also been known to graze on bathroom mould - a natural bathroom cleaner!
Common predators of red triangle slugs include frogs, reptiles, bats and birds.
Unlike snails, red triangle slugs lack a protective shell. Instead, red triangle slugs have an unusual defensive mechanism - they secrete a sticky mucus from their backs strong enough to superglue predators down to surfaces, allowing them to make a (slow) getaway. The stickiness of the mucus is so strong that it can leave predators pinned to a surface for days! Scientists are still trying to determine how red triangle slugs don’t get stuck to themselves when using this defense mechanism.
Slugs are hermaphrodites meaning they have both female and male reproductive parts. This makes it easy for slugs to find a mate.
Red triangle slugs lay eggs in damp areas of the forest floor. They are often laid under the surface or under a fallen log for protection.
Juveniles (young slugs) have a slightly different appearance to adults, lacking both the distinctive red triangle and red border around their body. Instead, juveniles have a triangle outlined in grey and three dark grey stripes running down their backs.
Red triangle slugs may live up to three years.
The Invertebrate Explorer digital book explores the incredible world of Australian invertebrates.
Students can use the book to investigate classification, features, adaptations and habitats of a variety of Australian invertebrates through narrated videos, stunning images, interactive activities and detailed text.
This book was designed by teachers to support the NSW Science and Technology K-6 Syllabus and NSW English K-6 Syllabus.
Content supports living world, Australian animals and class studies on invertebrates.
Australian Museum. 2021. Red triangle slug. [online] Available at: <https://australian.museum/learn/animals/molluscs/red-triangle-slug/>.
Bowler, J. 2019. This bizarre Australian slug has such sticky slime, it can 'superglue' its enemies. [online] ScienceAlert. Available at: <https://www.sciencealert.com/this-australian-slug-s-slime-is-so-sticky-it-can-glue-a-frog-down-for-days/>.
Queensland Museum. n.d. Red-triangle slug. [online] Available at: <https://www.qm.qld.gov.au/Explore/Find+out+about/Animals+of+Queensland/Molluscs/Gastropods/Land+snails+and+slugs/Red-triangle+Slug/>.
A pale pink colour variant of the red triangle slug - Triboniophorus graeffei near Dungog, Australia by Ros Runciman. CC BY-SA 3.0 (rotated)
Red triangle slugs encircle each other when mating. - "Red triangle slug_2390" by eyeweed. CC BY-NC-ND 2.0
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