# Stag Beetle — Facts, Threats & Conservation

*Lucanus cervus (Linnaeus, 1758) — family Lucanidae*

> The stag beetle (Lucanus cervus) is Europe's largest lucanid beetle at up to about 75 mm, with males bearing branched mandibles for wrestling; larvae live for years in rotting wood, adults emerge briefly in summer, and the species is Near Threatened.

**IUCN status:** Near Threatened in Europe — Britain's largest beetle and a dead-wood specialist  ·  **WARN range:** Europe, Southern England and Wales for the best-known populations

## Quick facts
| Fact | Value |
| --- | --- |
| Male length | Up to about 75 mm including mandibles |
| Larval stage | Three to seven years in rotting wood |
| Adult season | May to August, mainly at dusk |
| Diet | Larvae: rotting wood; adults: sap and fruit |
| Habitat | Dead wood in broadleaved woodland and gardens |
| IUCN status | Near Threatened (Europe) |

## Scientific classification
- **Kingdom:** Animalia
- **Phylum:** Arthropoda
- **Class:** Insecta
- **Order:** Coleoptera
- **Family:** Lucanidae
- **Genus:** Lucanus
- **Species:** Lucanus cervus

## Conservation status
- **Status:** Near Threatened
- **Population:** No reliable global estimate; locally common in strongholds
- **Trend:** Decreasing across much of European range
- **Assessed:** 2014
- **CITES:** Not listed
- Dead-wood removal in managed landscapes is the primary driver. The adult beetle is the visible tip of a multi-year larval life hidden in decay.

## Key facts: Stag Beetle
- Lucanus cervus is Britain's largest beetle; males use branched mandibles for territorial wrestling, not for biting people.
- Larvae feed on rotting wood in tree roots and stumps for three to seven years before pupating.
- Adults live only a few weeks in late spring and summer, feeding on tree sap and fruit.
- Loss of dead wood in parks, gardens and woodland is the main threat — tidiness removes the larval habitat.
- The IUCN lists the species as Near Threatened in Europe; it is a UK Biodiversity Action Plan priority species.
- Females are smaller with stronger jaws and are often mistaken for a different species entirely.

## Why the jaws are for wrestling, not hunting
Male stag beetles look formidable. The branched mandibles can exceed half the body length and are used to lift and push rival males off tree trunks and sap runs where females gather. Matches are slow shoving contests; the loser is flipped or driven away, rarely injured.

Females have shorter, much stronger mandibles suited to excavating rotting wood for egg-laying. Neither sex hunts with the jaws — adults drink sap and eat fallen fruit. The mandible size difference is classic sexual selection: males invest in weapons for mating access, females in tools for reproduction.

## Years underground in rotting wood
A stag beetle larva is a white grub feeding on decaying heartwood and root material, usually of broadleaved trees — oak, beech, ash and similar. Development takes three to seven years depending on food quality and temperature. The larva moults repeatedly, growing until it pupates in a soil chamber adjacent to the wood.

Adult emergence is synchronised to warm evenings in May to August. Males patrol territories on trunks and fly at dusk with a low buzzing flight. Within weeks they mate, females lay eggs in wood, and the adults die. The visible beetle is the brief final stage of a multi-year life almost entirely spent hidden in decay.

## Dead wood as a deliberate habitat choice
Modern woodland management often removes standing dead timber and fallen logs for safety and tidiness. Stag beetles need that material left in place — not necessarily ancient forest, but gardens with old stumps, parks with decaying trees, and hedgerows with buried root wood.

Log piles, leaving old tree stumps in situ, and avoiding compaction over root zones are practical measures that cost nothing and benefit other saproxylic insects too. Stag beetles are a flagship for a whole community of dead-wood specialists that disappear quietly when every fallen branch is cleared.

## Near Threatened and still declining locally
Lucanus cervus is listed as Near Threatened on the European Red List. Britain holds a significant western outpost; numbers are highest in the south-east, with scattered records elsewhere. Local extinctions follow suburbanisation of old orchards and sterilisation of park woodland.

Recording schemes rely on public sightings of adults at dusk — the beetles are conspicuous when they fly but easy to miss in larval form. A Near Threatened listing means the species is not yet Endangered but is moving in that direction without habitat reversal.

## What WARN does
WARN publishes free, sourced education for species whose habitat is removed by everyday land management. Stag beetles need rotting wood left in place — a requirement that costs nothing to provide and disappears when gardens and parks are over-tidied.

If this guide helps you understand wildlife and the pressures it faces, a gift to WARN supports habitat protection and free public education in our partner countries.

## Frequently asked questions: Stag Beetle
### What do stag beetles eat?
Larvae feed on rotting wood inside tree roots and stumps for several years. Adults drink tree sap and eat fallen fruit; they do not eat living wood or leaves.

### Where do stag beetles live?
Deciduous woodland, parks, gardens and hedgerows with rotting wood and old tree roots, mainly in southern and central Europe. Britain's strongest populations are in the south-east.

### Are stag beetles dangerous?
No. Males cannot bite with force through the branched mandibles; females can nip if handled but are not dangerous. Mandibles are for wrestling other males.

### How long do stag beetles live?
Adults live a few weeks in summer. The full life cycle is much longer because larvae spend three to seven years in rotting wood before emerging.

### How big are stag beetles?
Males reach up to about 75 mm including mandibles; females are smaller at roughly 30–45 mm. They are Britain's largest beetle.

### Why are stag beetles declining?
Loss of dead wood in gardens, parks and woodland removes larval habitat. Tidying away stumps, logs and rotting roots eliminates the years-long larval stage the species requires.

### Are stag beetles endangered?
The IUCN lists Lucanus cervus as Near Threatened in Europe. It is a priority species in Britain with local declines, though adults remain visible in stronghold areas each summer.

## Sources
- [IUCN Red List — Lucanus cervus](https://www.iucnredlist.org/species/157900/214154258)
- [People's Trust for Endangered Species — Stag beetle](https://ptes.org/campaigns/stag-beetles/)
- [Natural History Museum — Stag beetle life cycle](https://www.nhm.ac.uk/discover/stag-beetles.html)

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Full guide: https://worldanimalrescuenetwork.org/wildlife-guides/stag-beetle