Hemingway Cats

Polydactyly and Radial Hemimelia


  • Additional digits on paws of cats (normally have 5 on forelimbs and 4 on hindlimbs)
  • Snowshoe quality - alleged benefit to weight distribution on snow
  • Visibly appealing for uniqueness
  • Potential link to bilateral radial hemimelia (hypoplasia/aplasia) and radial agenesis,
  • Two Types:
  • Preaxial (Before first phalange, common)
  • Postaxial (After fourth phalange, rare)
Big image


  • First appearance suggested in early 1600s
  • Origin debated between Boston and England (Norway?)
  • Used as mousers and good luck charms on ships in 19th century
  • Documented in oil painting from 1876 (MCBFA 1970)
  • Published as rumor by Darwin in 1850s.
  • Currently found in North America, Europe, and Asia.
  • Iconic breeds: Main Coon and Pixie Bob
  • Nicknamed Hemmingway Cat from author's affinity
Interest Story on Hemingway Cats


  • Point substitution mutation of Pd gene
  • Autosomal Dominant
  • Ectopic expression of signaling molecule in developing limb
  • Mutation located at sonic hedgehog cis-regulator, notated as ZRS (Lettice et. al. 2007)
  • Variability in expression causes variability in phenotype

Genotypes (Hemmingway House)

-Approximately 50 cats currently reside at the Hemingway house.

-Approximately 50% have polydactyly

-Very little Gene Flow (most are descendants of Hemingway's original Polydactyl cat)

-Not subject to Natural Selection (no consequence to relative fitness)

-Assumed not a sexually selected trait

-Hardy-Weinberg equilibrium estimation (sample size too small to support with confidence)

p + q = 1

pp + 2pq + qq = 1

p = Polydactyl

q = normal

qq = .5 -> q = .71 -> p = .29

pp = .09

2pq = .41

Homozygous Dominant = 9%

Heterozygous Dominant = 41%

Homozygous Recessive = 50%

Of the 50 or so cats at Hemingway house, approximately 25 are homozygous recessive, 21 are Heterozygous Dominant, and 4 are Homozygous Dominant.

Size of sample increases susceptibility to genetic drift.


Uncertainty regarding origin of deformities, possibly a different mutation than harmless version of Pd mutation.

Radial Hypoplasia/Aplasia

  • Congenital underdevelopment or absence of part or all of the radius.
  • Relative frequencies uncertain due to abundance of breeders who practice without regulatory oversight.
  • Euthanasia without veterinary assistance, natural death or miscarriage may belie accurate data

Radial Agenesis -

  • Angular deformities in affected limbs.
  • Affliction in radius causes hyperplasia of Ulna, resulting in a larger diameter.

-Insufficient research linking polydactylism with radial deformities

Case Study - Auburn University

  • Two 10 week old kitten littermates (male and female) presented with sibling and mother (unnafected)
  • Polydactyl, radial hemmelia, radial agenesis, and cardiomegaly
  • Suggestive heritiability of traits and correlation between polydactylism and corresponding deleterious symptoms
Polydactyl Cats - A Lion in Your Living Room Tale


  • Targeted breeding due to appeal and resulting demand from consumers
  • Common Veterinary recommendations are to NOT use polydactyls for breeding
  • There are no current regulations in place regarding breeding of polydactyl cats


  • Cosmetic surgery for show quality
  • Targeted breeding may result in inbreeding; reducing genetic variation
  • Potential link with radial hemimelia may cause propagation of deformity
  • Twisty Cats - radial agenesis deliberately bred to reduce cat's ability to escape


The conclusion of the Lettice (et. al.) experiment suggests that there are multiple mutations which affect polydactyly in cats. One such mutation is deemed harmless and causes no biological compromises. However, variations on this mutation have the potential to cause sever congenital deformities.

Immediate: Breeding of polydactyl cats should be restricted or ceased until sufficient evidence supports the findings of Lettice et. al.

Long Term: Breeding polydactyl cats should only be permitted if the breed stock has been certified to contain the non-deleterious version of the gene. A regulatory agency needs to be created, enforcing carriers of the 'bad' mutation to be de-sexed, and enacting punishment on non-certified breeding of polydactyl cats.

Discussion Question

Without sufficient research to support causality of genetic deformities with Polydactyly, should breeding of Hemingway cats be regulated or banned?


1. Danforth CH. 1947. Heredity of Polydactyly in the Cat. Oxford Journal of Heredity 38 (4): 107-112

2. Lockwood A, Montgomery R, McEwen V. 2009. Bilateral Radial Hemimelia, Polydactyly and Cardiomegaly in Two Cats. Veterinary and Comparative Orthopaedics and Traumatology (VCOT) 6: 511-513

3. Lettice LA, Hill AE, Devenney PS, Hill RE. 2007. Point mutations in a distant sonic hedgehogcis-regulator generate a variable regulatory output responsible for preaxial polydactyly. Oxford Journal Human Molecular Genetics 17 (7): 978-985

4. MCBFA Scratch Sheet, Winter Quickie 1970

5. http://pawpeds.com/pawacademy/general/poly/

6. http://messybeast.com/poly-cats.html

7. http://messybeast.com/twisty.htm

8. http://vetbook.org/wiki/cat/index.php/Polydactyly

9. http://vetbook.org/wiki/cat/index.php/Radial_aplasia

10. Hemingway House data:


11. Images: