# Water Bear (*Milnesium tardigradum*)

> The water bear (Milnesium tardigradum) is a microscopic tardigrade famous for surviving vacuum, radiation, and decades of desiccation. Adults reach 1 mm and are Least Concern.

- **Category:** Invertebrate
- **Conservation status (IUCN):** Least Concern
- **Range:** Moss and lichen worldwide.
- **Canonical page:** https://globalanimalguide.org/animals/water-bear/
- **Last reviewed:** 2026-07-16

## Scientific classification

- **Kingdom:** Animalia
- **Phylum:** Tardigrada
- **Class:** Eutardigrada
- **Order:** Apochela
- **Family:** Milnesiidae
- **Genus:** Milnesium

## Facts at a glance

| Attribute | Value |
| --- | --- |
| Scientific name | Milnesium tardigradum |
| Diet | Carnivore (microbes) |
| Habitat | Moss moisture films |
| Lifespan | 1–2 years |
| Weight | 0.0000001–0.000001 kg |
| Top speed | up to 0.002 km/h |
| Conservation status | Least Concern (IUCN) |

## Eight-legged barrel of resilience

Tardigrades walk slowly on four pairs of clawed legs. A stylet mouth pierces plant and animal cells in moss films. Bodies are segmented yet microscopic.

## Moss films and lichens

They graze on plant cells, bacteria, and rotifers in thin water films on moss, lichen, and soil worldwide — including rooftops and Antarctica.

## Every continent including Antarctica

Milnesium tardigradum and relatives occur wherever a film of moisture persists. Distribution is essentially global.

## Indestructible at micro scale

Least Concern with untold billions. Cryptobiosis — tun formation — lets them survive extreme dryness, cold, and radiation experiments in labs.

## Frequently asked questions

### Can tardigrades survive in space?

Lab experiments exposed tun-state tardigrades to vacuum and radiation; many revived after rehydration.

### How do tardigrades survive drying out?

They curl into a dry tun, replacing water with protective sugars until moisture returns.

### How big is a water bear?

About 0.3–1 mm — visible only under a low-power microscope.

### Where do you find tardigrades?

In moss, lichen, soil, and roof moss anywhere with occasional moisture.

### Are tardigrades endangered?

No — they are among the most abundant and widespread micro-animals on Earth.

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Source: Global Animal Guide (https://globalanimalguide.org/animals/water-bear/). Licensed CC BY-NC 4.0 — free for non-commercial reuse with attribution.