Line breeding vs. inbreeding: What’s the difference?

When discussing genetics in small captive populations of hedgehogs and tenrecs, the terms line breeding and inbreeding often come up. They are closely related concepts, and in practice the difference lies mainly in intent and degree. Both involve pairing animals that share common ancestors, but the goals, risks, and outcomes can vary significantly.

What Is Inbreeding?

Inbreeding is the mating of animals that are closely related, such as siblings, parent to offspring, or animals that share a recent ancestor multiple times in their pedigree.

Goal: usually unintentional or due to limited genetic options.

Risks:

• High chance of doubling up on harmful recessive genes.
• Greater risk of inherited diseases (e.g., Wobbly Hedgehog Syndrome in hedgehogs).
• Inbreeding depression: reduced fertility, smaller litters, lower survival rates.
• COI (Coefficient of Inbreeding): Often rises above the safe threshold (registries advise staying under 4%).
• Inbreeding is generally considered harmful if repeated across generations without fresh bloodlines.

What Is Line Breeding?

Line breeding is a controlled form of inbreeding where breeders deliberately use more distant relatives (such as cousins, half-siblings, or grandparents to grandchildren) in order to preserve or strengthen desirable traits.

Goal: fix positive traits such as strong body type, spine quality, or temperament, while avoiding extreme genetic closeness.

Risks:

• Still increases COI, though less drastically than close inbreeding.
• May silently concentrate recessive health issues if not carefully managed.

Advantages:

• Helps stabilise a line with consistent traits.
• Can be safe if alternated with outcrossing to maintain diversity.

Key Differences

Aspect	Inbreeding	Linebreeding
Closeness of relation	Very close (siblings, parent-offspring)	More distant (cousins, half-siblings, grandparent-grandchild)
Purpose	Often due to limited options; not always intentional	Planned, to fix traits or maintain a bloodline
Risks	High risk of defects, recessive diseases, inbreeding depression	Moderate risk; safer if alternated with outcrossing
COI levels	Often >10%, dangerous long term	Ideally kept <4–6%, though still requires monitoring

Hedgehogs vs Tenrecs

Hedgehogs: Line breeding is sometimes used to stabilise colour traits or body type, but WHS risk makes careful COI monitoring essential. Inbreeding (close relatives) is strongly discouraged.

Tenrecs: Because captive populations are so small, even line breeding can be risky. Outcrossing between facilities and countries is far more important to preserve genetic diversity than fixing specific traits.

In Summary

• Inbreeding = close relatives, high risk, usually harmful in the long term.
• Line breeding = more distant relatives, controlled use, sometimes helpful to stabilise traits but still risky if overused.

Both increase the inbreeding coefficient (COI), which should stay below 4% to avoid serious genetic problems. Outcrossing remains the safest way to maintain health and vitality in both hedgehogs and tenrecs.