Banana Slug mating spiral.

Exceptions being where space is too constrained.
Banana Slug mantle spots visible through eggshell — alongside hatchlings.

Compare this hatchling's mantle spot with figures in the eggs.
Internal shell visible through the mantle of juvenile Banana Slugs.

Look for the cloudy shape beneath their mantle spot — also visible on those without.
12-Inch / 30cm Banana Slug

Banana Slugs are only documented elsewhere as being able to reach 10" (25cm)!
Clutch of Banana Slug Eggs
Banana Slug Mating Wounds

Holes indicated here in the tail and mantle.
Banana Slug penis upon mating separation.

Apophallation is the chewing off of the penis after mating — reported elsewhere with Banana Slugs as taking place ~5% of the time.
Sleeping Banana Slug

Homes being where they return for rest on more than one consecutive day.
Banana Slug nibbling during courtship.
Banana Slug suspended in a Scotch Broom shrub.

Banana Slugs often feed on both the leaves and flowers of this invasive shrub.
Banana Slug courtship chase.

The pursued may even whip their tail out of the way.

Adult Banana Slug with hatchlings.
Main Page Guides

Banana Slug Notes & Care

Jump to: Notes | Care

Despite their popularity, Banana Slugs (Ariolimax) aren't nearly as understood as many other gastropods — likely as their low temperature requirements and narrow distribution limit captive study.

Since 2022, I've observed Button's Banana Slugs (A. buttoni) almost daily along the Mendocino Coast, and in early '24 began caring for my first in captivity. While the following guide will focus on this experience and their nuances, it should at least loosely apply to any of the genus.

Wild yellow Banana Slug.

Notes

Based on Personal Observation

General Behavior

  • Semi-arboreal, as their daily rest is often split between ground level and heights of up to ~15' (4.5m). This tendency to alternate resting elevation continues in captivity — despite a static climate. Fully arboreal activity is also common in the wet seasons wherever elevated food is available — such as amongst Scotch Broom.
  • Rests on the ground are almost always a home — lasting as long as 2 months before being abandoned.
  • A high degree of spatial awareness was recorded in captivity on multiple occasions, where an individual fleeing courtship returned to their pursuer upon lost contact. On each occasion the pursued took a direct but different path of return to the point of last interaction, suggesting the ability to form a scent map rather than simply backtrack upon one's own path.

Climate Tolerance

  • Their preferred temperature is ~55°F (13°C), as determined through their home distribution on a thermal gradient. Found later to be corroborated by the feeding observations on page 105 of The Foraging Ecology of the Banana Slug — a great dissertation on the Pacific Banana Slug (A. columbianus).
  • When lacking a moist surface, signs of stress appear below ~65% RH, as slime production sharply increases and activity diminishes.

Age Markers

Banana Slug Age Markers

Reproduction in Captivity See Conditions

  • Sexual maturity is reached at ~5 months of age.
  • Mature individuals tend to court any conspecifics they bump into — including hatchings. This involves persistent nibbling, which typically leaves scars and may eventually result in fully-punctured skin. If reciprocated, they focus on their partner's right flank until their gonopores align — otherwise, a chase ensues until either reciprocation or lost contact. Fleeing doesn't necessarily mean disinterest, as the pursued will occasionally return to their pursuer upon separation — suggesting overstimulation. Courtship takes ~1 hour, and if successful, typically concludes in a Yin-Yang spiral.
  • Mating begins shortly after gonopore alignment, and involves 12–24 hours of simultaneous penetration. This range was consistent across the climate's gradient.
  • Beginning at ~5 months old, a single pair mated every 4–7 days over the course of 4 months — totaling 23 sessions before this tracking ended due to the trend's stability. However, this couple became much more sedentary at ~12 months of age, which resulted in fewer encounters and prompted tracking to resume at ~13 months of age. They were then found to be mating every 6–12 days over the course of 2 months — totaling 7 sessions.
  • No signs of apophallation were ever found, as all observed matings involved two penises.
  • Eggs may be laid at as young as 8 months old, and take ~6 weeks to hatch.
  • The largest brood was 65 and a result of self-fertilization, with only one individual falling noticeably behind the others' growth.

Morphology

  • Hatchlings exhibit faint tail spots until either fading away or becoming more defined by ~3 weeks of age.
  • Even when self-fertilized, the final presence and composition of spots varies wildly within a given brood.
  • The best indication of whether a juvenile will maintain tail spots is the presence of a mantle spot. Such spots are typically associated with spotted tails in adults, and fully-develop within the egg at ~1 month. When the fetus is suitably oriented, the mantle spot is visible through the eggshell.
  • It's exceptionally rare for a spotted individual to have more or fewer than one mantle spot, which when present is directly above their internal shell, which is in turn visible through the mantle until ~2.5 months of age.

Timelapses of specific behavior as well as additional pictures are available upon request.

See site's Main Page for means of contact.

Successful Care

Captive Banana Slug

Meet Lil' Shrimp — my first Banana Slug. I adopted him at about an inch long, and over the course of 14 months watched him grow into a giant 12" (30cm) slug. It's thanks to him and his babies that I'd first learned much of the following.

Diet

Acceptance Sources Used
Leafy Greens Daily Dandelion, Hawksbeard, Sow Thistle, Clover Sprouts
Pollen Semiweekly Bee Pollen, Dandelion Flowers
Carrot Semiweekly Dried Carrot Chunks
Apple Semiweekly Dried Apple Rings
Oats Semiweekly Rolled Oats
Minnow Weekly Freeze-Dried Minnow

Staple foods — containing vital nutrients.

Hydrate dry goods to avoid harmful expansion in the gut.

Climate

Temperature

  • Substrate's surface features a constant range of 55–65°F (13–18°C) by means of a height gradient and custom substrate cooler, while the enclosure's lid is ambient (~72°F or ~22°C in my case).

Hydration

  • Enclosure is fogged for 15 minutes every 12 hours, which maintains a moist substrate and vertical RH gradient of ~75% to ambient (~55% in my case).
  • Alternative success also found with a moist substrate and directly misting each slug at least once per day. Consider ~60°F (15°C) water to minimize thermal shock.

Enclosure

Size

  • 32-Gal (120L)
  • 24"W x 18"D x 18"H (60 x 45 x 45cm)
  • Suitable for up to two adults, as they engage in courtship upon most encounters with each other, which is often stressful.

Substrate