Banana Slugs Mating
Banana Slug Mantle Spot in Eggshell

Compare this hatchling's mantle spot with figures in the eggs.
Banana Slug Internal Shell

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

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

Holes highlighted here in the tail and mantle.
Banana Slug Home

Homes being where they return for rest on more than one consecutive day.
Banana Slug Nibble
Adult Banana Slug with Hatchlings
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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.

I've observed coastal populations of Button's Banana Slugs (A. buttoni) almost daily since 2022, 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 Banana Slug

Notes

Based on Personal Observation

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.

General Behavior

  • Very timid outside of courtship, to the point that they're often chased off by smaller species — such as the Grey Field Slug (D. reticulatum).
  • About half of their daily rest is spent at ground-level, with the remainder at heights of up to ~10' (3m). This tendency to alternate resting elevation continues in captivity, despite a static climate.
  • Rests on the ground are almost always a home, which may last up to 2 months before being abandoned.

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. This process takes ~1 hour and with enough space concludes in a Yin-Yang spiral. However only ~20% of encounters see mutual interest, as targets often rapidly evade and lose their pursuer in a chase.
  • Copulation begins shortly after gonopore alignment, and involves 12–22 hours of simultaneous penetration.
  • Over the course of 4 months a single pair mated 24 times (every 4–7 days), followed by ~1 day of disinterest in each other. These engagements were observed at all points within the climate gradient, and with no clear duration trend. Tracking stopped arbitrarily rather than due to a change in this behavior.
  • 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 noticeably falling behind the other's 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 appropriately 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.
Banana Slug Growth Markers

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 their conspecifics. Courtship can be stressful, and with two adults it occurred almost daily within this confine.

Substrate