This is an introduction to the Royal Kennel club’s Population Analysis for the Whippet which was published in January 2026. To safeguard and manage genetic diversity, breeders need to be able to make informed decisions based on the specific characteristics of the breed. Here, the UK’s Breed Health Coordinator, Jo Whitehead, has highlighted some of the key findings from the report.
Genetic diversity and why it is important
- Essential for long-term breed health
- Reduces inherited diseases
- Improves adaptability and survival
Genetic diversity in the UK’s Whippet population matters because it underpins the breed’s long-term health, resilience, and ability to avoid inherited disease. A genetically varied population is better able to maintain strong immune function, reduce the expression of harmful recessive conditions, and sustain healthy fertility and lifespan. Whippets already show signs of narrowing diversity through selective breeding and the popular sire effect, which can concentrate genetic risks and reduce overall robustness. Maintaining diversity helps preserve the breed’s physical soundness, behavioural stability, and adaptability for future generations.
Factors that reduce diversity
- Small population size
- Limited migration/imports
- Overuse of certain sires
- Strong selection for specific traits
- Inbreeding
The breed population in the UK experienced a significant increase in size between 1990 and 2021 with breed registrations more than tripling in this time. Post 2021 there has been a sharp decrease in registrations likely attributable to the ‘Covid effect’.
In the UK, only 4.4% of the breed have Stud Book numbers (SBN) and just 0.8% hold UK Champion titles. We must consider the effect of these on breeding choices.
Inbreeding and the Coefficient of Inbreeding (COI)
Inbreeding is defined as the mating of closely related dogs.
- The COI measures probability of identical gene copies and includes bad as well as good.
- The greater the COI, the more shared ancestors there are.
The average COI for Whippets born in 2021 was 10.2%. The average genetic relatedness among living Whippets in the UK is 14.1%, meaning the typical dog is more closely related to others in the breed than first cousins, though not as closely as half-siblings.
Effective Population Size (Ne)
Ne is used to calculate how fast diversity is lost within a population. For Whippets, it is influenced by the number of dogs contributing to the gene pool, sex ratios, and any bottlenecks.
It is measured as –
- Ne < 50: critical risk
- Ne 50-100: endangered
- Ne > 100: more sustainable
The effective population size in UK Whippets is Ne 74 so the breed is losing genetic diversity faster than it can maintain it. This puts us in a genetically vulnerable zone.
Inbreeding Depression
This is well documented across many species and is linked to reduced survival, impaired reproduction and greater susceptibility to disease. Rapid increases in inbreeding raises the risk of Inbreeding Depression and with an effective population size of Ne 74, the UK Whippet population is at risk. The analyses show there was a significant and negative association between COI and litter size in the breed with litters born with a higher COI tending to be smaller.
Imported dogs
Importing dogs can add new genetic variation but the effect depends on how long the populations were separated – short pedigrees may hide a shared ancestry. The number of imported Whippets has significantly increased over time, with a concurrent and relative increase in the percentage of litters produced from imported parents.
Popular sire effect
Overuse of a particular sire reduces diversity and spreads harmful variants quickly. No single dog should dominate the gene pool. Across time, there has been strong evidence of popular sire use in Whippets. Even though Whippets are numerically large, when only a small proportion of males are used for breeding, the breed’s genetic diversity is compromised. The report shows that sires with SBNs have significantly higher numbers of litters compared to those that don’t have an SBN.
Pedigree vs DNA inbreeding
A dog’s pedigree tracks ancestry and assumes unrelated founders. A dog’s DNA measures genetic similarity.
Whippets have a relatively small effective population size and a high degree of relatedness, which means pedigree breeding practices can easily drift into unintentionally close breeding. This in turn increases the risk of inherited disease and inbreeding depression unless genetic diversity is actively managed. Sustainable breeding is less about avoiding all inbreeding – which is impossible in a closed stud book – and more about controlling how fast it accumulates.
Jo Whitehead
UK Whippet Breed Health Coordinator