Chihuahua

Chihuahua: median survival age, UK veterinary clinic population

• UK primary-care veterinary clinic population (VetCompass), not a census of all dogs of the breed.
• Hazard ratio vs. the crossbred reference group: 1.17 (95% CI 1.13-1.21, p<0.001).

Chihuahua: life expectancy at birth, UK veterinary clinic population

• UK primary-care veterinary clinic population (VetCompass), not a census of all dogs of the breed.
• Life expectancy at birth (cohort life-table method), a different statistic from a Kaplan-Meier median survival age -- do not compare directly against McMillan 2024's figures.

Chihuahua: body size class -- Small

• Body size and cephalic index classification per Supplementary Table S5; for breeds absent from the study's primary source lists, assigned by majority agreement among Dogs Trust canine-behaviour experts rather than measured directly on dogs.

Chihuahua: head-shape (cephalic index) classification -- Brachycephalic

• Body size and cephalic index classification per Supplementary Table S5; for breeds absent from the study's primary source lists, assigned by majority agreement among Dogs Trust canine-behaviour experts rather than measured directly on dogs.

Chihuahua: UK Kennel Club group: Toy; FCI group: Companion and Toy Dogs

• KC/FCI group columns record nomenclature presence only, per the table's own caption -- the study did not use group as an analysis variable.

Chihuahua: hip evaluations rated dysplastic (mild/moderate/severe combined), OFA cumulative statistics

• OFA is a voluntary-submission registry: owners/breeders choose whether to have a dog evaluated and whether to submit the result, so this is not a random sample of the breed and most likely understates true population prevalence.

Chihuahua: share of surveyed dogs scored high on the Fear trait (Salonen 2020, Finnish pet dogs)

• Self-selected online convenience sample of Finnish pet owners, not a random sample of the breed or of all dogs.
• Restricted to breeds with at least 50 surveyed dogs to avoid small-sample noise.

Chihuahua: share of surveyed dogs scored high on the Noise sensitivity trait (Salonen 2020, Finnish pet dogs)

• Self-selected online convenience sample of Finnish pet owners, not a random sample of the breed or of all dogs.
• Restricted to breeds with at least 50 surveyed dogs to avoid small-sample noise.

Chihuahua: NYC bite reports per 1,000 licensed dogs of this breed, all years combined

• One city only (NYC); breed labels are self-reported, not verified against a registry or genetic test.
• Licensed-dog counts are active-license snapshots per extract year, not a true owned-dog population.

Chihuahua: purpose class 'toy', from FCI group: Companion and Toy Dogs

• Registry group membership at time of the source table, not an independent behavioural assessment.

Chihuahua, long-haired: average litter size, Danish Kennel Club registrations Aug 2022-Jul 2023

Chihuahua, smooth-haired: average litter size, Danish Kennel Club registrations Aug 2022-Jul 2023