How to spot extreme breeding traits

Anyone who wants to buy or breed a pet should take a close look—especially at traits that could harm the animals. This includes genetically modified or dyed animals.

Some breeding traits can make pets sick: Dogs with large, round heads and short jaws and muzzles often have respiratory problems as well as thermoregulatory problems due to panting problems or even sleep apnoea. 

Cats with folded ears carry a genetic defect that leads to severe cartilage defects and joint pain.

Certain color morphs of reptiles can entail a greater risk of cancer or neurological harm.

Dogs

• Brachycephaly → airways stenosis with respiratory difficulties up to shortness of breath, impaired thermoregulation (heat buildup) due to impaired panting, limited communication behavior, sleep apnoea (e.g., in some pugs, Cavalier King Charles Spaniels, and French bulldogs)
• Excessive skin folds → inflammation, itching, misalignment of the eyelids (entropion)
• Extremely short legs / long back → elbow dysplasia, disc problems, paraplegia (e.g., in some dachshunds)
• Sloping back → movement disorders, osteoarthritis, spinal problems (e.g., in some German shepherds)
• Color variations or breeds → associated with blindness, behavioral disorders, or organ problems

Cats

• Folded ears → cartilage defects, joint pain (e.g., in Scottish Folds)
• Brachycephaly → respiratory, visual, and dental problems (e.g., in some Persian cats)
• Hairless cats → no protection from cold, drafts, or heat

Small Mammals

• Dwarfism → Malocclusion due to shortened skulls, tendency to herniated discs
• Brachycephaly → Respiratory, eye, and dental problems (e.g., in some ermine rabbits)
• Excessively long ears → Prone to ear problems
• Disturbed hair growth, even hairlessness (especially in some guinea pigs, rats, and hamsters)
• Taillessness (e.g., certain breeds of rats)

Birds

• Short beak → Young birds may have problems in opening eggshells upon hatching
• Crested feathers → Birds' vision is impaired, possibly causing constant eye irritation (e.g., in some canary or budgie breeds)
• Excessive feather growth → Impairment of the sensory organs, eyes, and beak
• Posture → Birds sit or stand unnaturally on perches (e.g., in some canary breeds)

Reptiles

• Certain color variations → inflammation, tumors (e.g., Lemon Frost gecko), neurological disorders (e.g., wobblers in some giant snakes), albinism (risk of UV damage).
• Reduced or missing scales → changes in water balance, increased risk of injury, risk of UV damage.

Fish

• Missing dorsal fins or altered tail fins → shapes that no longer allow species-appropriate locomotion.
• Growths in the eye area → e.g., tissue growths on the head and eyes that appear telescopic or point unnaturally upward and impede the field of vision.
• Shortened and curved spine / balloon shape → severely shortened or curved spine that impedes appropriate locomotion.