Blue-grey Taildropper
(Prophysaon coeruleum)

This tiny blue endangered slug is a native species that can drop their tails if frightened and is a very rare sight to see

COSEWIC Status: Threatened

SARA Status: Threatened

Provincial Status: S2S3 (Imperiled, Special Concern)

BC List Status: Blue (Special Concern, Vulnerable)

The Blue-grey Taildropper is a small slug associated with two endangered ecosystems: Garry oak meadows and mature Douglas-fir forests. Little is known about the slug except that it is extremely rare and that its habitat is shrinking. This slug is endangered due to its rarity and threats to its habitat from development and other human activities.

Size: 4cm (adults) and 5mm (juveniles).

Colour: Solid colour from blue to pale grey, often with some fine white speckling. Distinct parallel grooves and ridges on the back and sides of tail.

Identification

In Canada, all records of the Blue-grey Taildropper are from 12 moist forests on southern and south-eastern Vancouver Island. Many records are from Garry oak meadows and their fringes. The slugs also occur in Douglas-fir-dominated forests, especially in small openings with dense shrubs such as ocean spray. The slugs are found in moist microsites on the forest floor, like under leaf litter and sword ferns, within moss, or under decaying logs.

Distribution & Habitat

Not much is known about these slugs as they are difficult to find and ocurr in low numbers. However, biologists have been able to examine Blue-grey Taildropper’s droppings to determine their diet. In Oregon, biologists found fungal spores in 90% of the droppings examined. The spores were mostly from mycorrhizal fungi that form essential symbiotic associations with tree roots.

Diet & Biology

Blue-grey Taildroppers face habitat degradation and loss through land modification such as urban development. Invasive plants displace native plants which harms Blue-grey Taildropper through decreased habitat quality, altered microclimates and possible food availability. Introduced and/or invasive animal species cause increased competition for habitat, food, and shelter, as well as increased predation (likelihood of being eaten). Slugs love and need water to move and breathe, so more droughts associated with climate change will impact the Blue-grey Taildropper’s ability to forage and go about their slug-y lives.

Threats

The Blue-grey Taildropper relies on Garry oak and Douglas fir ecosystems - both of which are endangered.

This puts every species who lives in them at greater risk.

Why do we care?

Mycorrhizal fungi, believed to be the main food source for the Taildropper, grow on the roots of plants and trees and help them capture nutrients from the soil. This relationship between beneficial fungi and trees is essential for healthy forests. In areas where mycorrhizal fungus/plant relationships have broken down, trees take longer to grow and are not as healthy. The Blue-grey Taildropper and the few other animals that eat these fungi play a vital role in spreading the spores of mycorrhizal fungi, and each time one of these spore-spreading species is lost, the entire forest suffers.

Apart from its ecological role, the Blue-grey Taildropper has intrinsic value as a unique inhabitant of Garry oak meadows and coastal Douglas-fir forests.

All photos are credited to Kristiina Ovaska

What is HAT doing to help?

Monitoring

In local parks, and on private land with appropriate habitat and interested landowners, HAT will set up artificial cover objects (ACOs) that Blue-grey Taildroppers like to shelter under. This allows us to check the cover objects without disturbing the natural habitat. Understanding the range and the habitat preferences of this small slug is an important step to protecting the species.

Public Land and Large Land Managers’ Stewardship

HAT helps the public and other large land managers in the CRD care for Blue-grey Taildroppers by identifying occurrences, outlining steps for protection, training staff to look and care for Blue-grey Taildroppers, and when appropriate, developing management plans to help protect the slug and its habitat. Where Blue-grey Taildroppers are located, HAT works to conserve the population and their habitat through voluntary, non-legally binding agreements (stewardship agreements), and voluntary, legally-binding agreements (e.g. covenants).