Mycelarium Animals: Defence That Actually Works

Animals are the only real pressure in Mycelarium. Crows and squirrels steal mushrooms, hedgehogs and boars wander the surface, and a frontier base without defence will lose structures while you are underground. The game gives you two tools: the Stinky Mushroom for passive area denial and the Repeller Mushroom for active scaring. Used together, they cover almost every situation.

This guide explains what each animal does, the layout that players report working, and the upgrades that make defence automatic.

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Which animals are dangerous?

• Crows and squirrels steal mushrooms. They are the reason a frontier Predator disappears. The achievement Red Alert asks you to scare off crows and squirrels ten times.
• Hedgehogs wander the surface and trigger the Fight back and Hold your ground achievements when scared with a Repeller. They are also the subject of Hedgehog Bus.
• Boars roam the surface. They are large, visible and disruptive; treat them as a reason to keep production inside the defended zone.

The starting mushroom is safe from harassment. Everything you build beyond it is not.

Stinky or Repeller?

They solve different halves of the problem:

• Stinky creates a smell radius that animals avoid. It is passive, permanent while it lives, and best for protecting a zone.
• Repeller actively scares an animal. It has a cooldown and two upgrades: Auto Regen and Regen Cost. It is best for clearing an approach.

A zone with only a Stinky is safe until an animal spawns inside the radius. A zone with only a Repeller is safe until the cooldown runs out. Together they cover both cases.

What is the two-tree layout?

Players describe a surface defence built around a pair of trees:

1. Place a Stinky Mushroom in the middle, between the two trunks.
2. Place a Repeller on each outer edge, facing the direction animals come from.
3. Put a Water Mushroom at each tree.
4. Upgrade Repeller Auto Regen first.

The Stinky covers the gap between the trees, the Repellers push animals away before they reach the trunks, and the Water Mushrooms keep the local branch supplied. It is compact, easy to read and covers the two most valuable assets on the surface: the trees and the food production around them.

How do you find the animals?

Update 1.02 added clickable animal icons on the screen edge. Click one to jump the camera to that animal. This is the fastest way to check what is chewing on a mushroom without panning across the map.

The tracker is also a warning system: if an icon appears near a new base, the base needs defence before the next visit.

Which upgrades make defence automatic?

• Repeller Auto Regen — the key upgrade. It keeps the Repeller firing without manual input.
• Repeller Regen Cost — makes the automatic cycle cheaper.
• Stench Width — covers more assets with the same Stinky.

Buy Auto Regen before Stench Width if you are defending a small base; buy Stench Width first if you have one Stinky covering a wide cluster. The upgrade priority guide→ puts both in the mid-game phase.

What should you do when a mushroom is stolen?

Replace it, then fix the defence before replacing it again. A stolen mushroom is a signal, not an accident. If the replacement is stolen within a minute, the base has no real coverage.

The cheapest emergency fix is a Repeller next to the replacement. The permanent fix is the two-tree layout or a Stinky covering the whole cluster.

Do animals attack underground?

The confirmed thieves and wanderers are surface animals. Underground hazards are environmental: hard soil, stone and limited water. If a deep branch disappears, look for a different cause before assuming an animal did it.

Do animals affect achievements?

Yes. Three achievements are tied to defence:

• Fight back — use a Repeller on an animal once.
• Hold your ground — use a Repeller on an animal 20 times.
• Red Alert — scare off crows and squirrels 10 times.

These are easy to earn while defending a real base. Do not farm them by letting animals destroy production; the achievements count the scares, not the losses.

FAQ

What scares hedgehogs?

The Repeller Mushroom. The achievements confirm that using it on an animal counts, and hedgehogs are the most common surface target.

Do Stinky Mushrooms kill animals?

No. They push animals away from a radius. The animal remains on the map.

Can animals eat the starting mushroom?

Players report the starting mushroom is safe. The danger begins with structures you add.

Is defence needed in Exploration Mode?

Yes. Exploration Mode has fewer animals than Survival, but the thieves still spawn and still take mushrooms.

Official source: Mycelarium on Steam ↗ Official source: Update 1.02 notes ↗

The Steam discussions hub ↗ contains the original player description of the two-tree layout; the achievement page ↗ shows the unlock rates for the Repeller milestones.