Breeding Whippets

Complete Guide for Responsible Breeders

Breeding Whippets requires understanding the breed's unique genetic profile, including the myostatin mutation that creates both performance advantages and health challenges, plus critical awareness of sighthound-universal anesthesia sensitivity and the genetic basis of mitral valve disease. This guide provides comprehensive breed-specific information for mid-level breeders focused on producing healthy, structurally sound Whippets that honor the breed's coursing heritage while managing known hereditary conditions.

Breed Overview

The Whippet was developed in England during the 19th century, primarily by coal miners in the North who wanted a smaller, faster dog for rabbit coursing and racing. Often called the "poor man's racehorse," Whippets were bred down from Greyhounds with terrier and Italian Greyhound crosses to create a medium-sized sighthound that could excel in coursing competitions and rag racing. The breed's name likely derives from "wappet," an old English term for a small, quick dog.

The AKC recognized the Whippet in 1888, three years before the English Kennel Club, making it one of the earlier recognized breeds in the United States. Today, Whippets maintain their coursing heritage while also excelling as companion dogs, show dogs, and in lure coursing and racing events. The breed currently ranks 50th in AKC popularity, maintaining stable registration numbers among sighthound enthusiasts who value the breed's combination of speed, elegance, and gentle temperament.

Like their larger cousin the Irish Wolfhound, Whippets are built for speed and endurance with deep chest capacity and powerful rear drive. However, at 18-22 inches tall and 20-40 pounds, Whippets are far more manageable in size while retaining full sighthound hunting instincts. The American Whippet Club serves as the AKC parent club, offering extensive breeder education resources and health research programs.

Breed Standard Summary for Breeders

Whippets are medium-sized sighthounds combining elegance and fitness with muscular power for speed and endurance. The standard emphasizes beautifully balanced muscular power and strength combined with great elegance and grace of outline. Symmetry, muscular development, and powerful gait are essential—Whippets are built for speed and work, requiring a combination of muscular power with maximum flexibility and minimum weight.

Size specifications (critical for breeding decisions):

Males: 19-22 inches at withers, typically 25-40 pounds

Females: 18-21 inches at withers, typically 20-35 pounds

CRITICAL HEIGHT DISQUALIFICATION: More than one-half inch above or below stated height limits. This is an absolute DQ and eliminates breeding prospects. Measure carefully at 24+ months when structure is mature.

Eye and bite disqualifications:

• Blue eye or eyes (any portion of blue)
• Eyes not of the same color (heterochromia)
• Undershot bite
• Overshot bite one-quarter inch or more

Key structural priorities for breeding stock:

• Correct shoulder angulation (well laid-back) and upper arm length—critical for reach
• Deep brisket reaching to elbows for heart and lung capacity
• Strong, slightly arched loin providing driving power
• Correct rear angulation with well-bent stifle and low-set hocks
• Long, lean head with small rose ears and keen expression
• Level topline with gentle arch over loin
• Athletic, balanced outline with visible muscle definition
• Powerful, ground-covering gait with excellent reach and drive

Serious faults affecting breeding decisions:

• Short or steep upper arm (reduces reach)
• Straight shoulder placement
• Elbows turned in or out
• Weak pasterns
• Long or soft topline
• Flat croup
• Shallow or narrow chest
• Straight stifle (reduces drive)
• Cow hocks or sickle hocks
• Poor reach and drive

The Whippet standard allows any color or mixture of colors with no color disqualifications, providing breeders with exceptional flexibility in color breeding programs.

Whippet Reproductive Profile

Whippets typically produce litters averaging 6 puppies, with a normal range of 1 to 10 puppies per litter. The breed has a relatively low C-section rate of approximately 10%, with most bitches whelping naturally due to their medium size, athletic build, and moderate puppy size. Natural whelping is the norm and should be expected with proper prenatal care and monitoring.

Fertility considerations specific to Whippets:

First heat timing: Whippet bitches typically have their first heat between 12-24 months, notably later than many breeds. Some individuals may not cycle until 9 months, while others may be as late as 3+ years. This variability is normal in the breed and does not indicate fertility problems. Plan health testing schedules accordingly.

Heat cycle intervals: Individual variation is common, with 6-9 month intervals typical. Track each bitch's pattern carefully as it establishes her normal cycle.

Cryptorchidism: Undescended testicles occur at low to moderate frequency in Whippets (approximately 8% prevalence based on breed data). This is a hereditary condition with a 13x higher testicular cancer risk. Cryptorchid males should NOT be bred and are disqualified from conformation showing. Check puppies at 6-8 weeks and recheck at 6-8 months to confirm both testicles have descended.

Lean body condition essential: Whippets are naturally lean, athletic dogs. Maintaining proper body condition (visible ribs with minimal fat cover) throughout the bitch's reproductive life is essential for natural whelping success. Overweight bitches face increased whelping complications despite the breed's generally easy whelping reputation.

AI suitability: Natural breeding is strongly preferred and usually successful due to the breed's medium size and athletic build. Fresh or chilled AI is used when natural breeding is not possible due to distance or timing challenges. Frozen AI is available but less commonly used. The breed does not typically require AI for anatomical reasons—if breeding problems occur, evaluate male fertility and timing rather than assuming AI is needed.

Breeding Age and Timeline

First heat expectations: Whippet bitches typically experience first heat between 12-24 months, with normal range extending from 9 months to over 3 years. This is notably later than many breeds. Do not assume fertility problems if a bitch does not cycle until 18+ months—this is within normal breed variation.

Recommended first breeding age:

Females: 24 months (2 years) minimum. This allows time for complete health testing including OFA cardiac evaluation at 24 months, plus full structural maturity assessment. Breeding on the second or third heat after 24 months is ideal.

Males: 12-18 months minimum after health testing completion. Males can be used for stud service once BAER hearing test, eye exam, and cardiac evaluation are complete and results are normal. However, many breeders prefer waiting until males have proven themselves in performance events or conformation showing.

OFA cardiac evaluation minimum age: 24 months for baseline echocardiogram. This is essential given the breed's predisposition to mitral valve disease with genetic basis on chromosome 15.

Maximum litters per bitch: 5 litters maximum over the bitch's lifetime. Given the breed's low C-section rate and moderate litter sizes, some bitches could physically produce more, but limiting to 5 litters preserves long-term health and quality of life.

Retirement age: No later than 8 years. Many breeders retire bitches earlier (6-7 years) to ensure quality of life in senior years.

Complete breeding timeline:

1. 18-24 months: Complete all baseline health testing (CAER eye exam, cardiac echo, BAER hearing test, optional thyroid panel and hip evaluation)
2. 24+ months: First breeding eligibility after second or third heat
3. Each breeding: Update progesterone testing for optimal timing, maintain current eye exams (annual requirement)
4. Every 2 years: Repeat cardiac echocardiogram for breeding bitches (mitral valve disease is progressive and age-related)
5. 6-8 years: Retirement age for bitches
6. Ongoing: Males can be used for stud service as long as health testing remains current and fertility is proven

Required Health Testing

The American Whippet Club's CHIC requirements mandate three specific tests for breeding Whippets. All tests must be registered with OFA (Orthopedic Foundation for Animals) for CHIC certification, though passing results are not required—the goal is transparency in health data reporting.

CHIC Required Tests:

CAER Eye Examination (Companion Animal Eye Registry)

Screens for: Progressive retinal atrophy (PRA), cataracts, lens luxation, and other congenital eye abnormalities including conditions that can lead to blindness

Frequency: Annual examination required. Eye disease can develop at any age, and breeding stock must be screened yearly.

Cost: Approximately $100 per exam

Testing protocol: Performed by a board-certified veterinary ophthalmologist. Results registered with OFA/CERF database.

Cardiac Echocardiogram (Advanced Cardiac Evaluation)

Screens for: Mitral valve disease (MVD/MMVD), which is overrepresented in Whippets and has a genetic basis identified on chromosome 15. Echocardiography allows visualization of valve structure and blood flow patterns to detect early disease.

Frequency: Minimum every 2 years for breeding stock. Many breeders perform annual cardiac screening due to the breed's high MVD prevalence.

Cost: Approximately $515 per echocardiogram

Testing protocol: Performed by a board-certified veterinary cardiologist. Results registered with OFA cardiac database. Note that mitral valve disease shows age-related penetrance (older dogs more likely to develop), making it difficult to identify truly clear control dogs. Screening should continue throughout a dog's breeding career.

BAER Hearing Test (Brainstem Auditory Evoked Response)

Screens for: Congenital deafness (unilateral or bilateral), which is especially important in white and merle Whippets due to pigment-associated deafness risk

Frequency: One-time test (congenital condition present from birth)

Cost: Approximately $215

Testing protocol: Performed by specialized veterinary neurologists or universities with BAER equipment. Detects hearing loss that cannot be identified by behavioral observation alone—unilaterally deaf dogs appear normal but should not be bred. Results registered with OFA.

BAER testing is CRITICAL in Whippets because the breed's "any color" standard includes white and merle, both associated with pigment-linked deafness. White on or near the ears is an indicator of potential lack of pigment cells in the inner ear.

Total CHIC-required cost per dog: Approximately $830 for initial baseline testing, plus ongoing annual eye exams ($100/year) and biennial cardiac evaluations ($515 every 2 years).

Additional Recommended Tests (not CHIC-required but valuable):

Myostatin Deficiency DNA Test

Screens for: Myostatin mutation causing Bully Whippet syndrome (double-muscling). Identifies carriers (heterozygotes) who show enhanced racing performance and affected dogs (homozygotes) with health issues.

Cost: Approximately $65

Why test: Heterozygous carriers have increased muscle mass and enhanced racing performance with no health consequences. However, breeding two carriers together produces a 25% chance of homozygous "bully whippets" with extreme muscle hypertrophy, structural issues, and potential quality of life concerns. Testing allows informed breeding decisions.

Hip Evaluation (OFA or PennHIP)

Screens for: Hip dysplasia, which is uncommon in Whippets but documented in the breed

Cost: Approximately $150

Why consider: While not a major breed concern, hip screening provides valuable data for breeding decisions, particularly in lines with any history of lameness or mobility issues.

Thyroid Panel (OFA Thyroid Registry)

Screens for: Autoimmune thyroiditis and hypothyroidism

Cost: Approximately $130

Why consider: Provides baseline thyroid function data. Hypothyroidism can affect fertility and coat quality.

Hereditary Health Conditions

Whippets face several hereditary health conditions that responsible breeders must understand and screen for. The most significant are the myostatin mutation (with its unique heterozygote advantage), mitral valve disease with identified genetic basis, and near-universal anesthesia sensitivity shared with all sighthounds.

Myostatin Deficiency (Bully Whippet Syndrome)

Prevalence: Homozygous affected dogs are rare; heterozygous carriers estimated at 5-15% of the breed population

Inheritance: Autosomal recessive with incomplete dominance—heterozygotes show intermediate phenotype

DNA test available: YES (commercially available from multiple labs)

Clinical presentation:

• Homozygotes (bully whippets): Extreme muscular hypertrophy visible from birth, broader head, pronounced overbite due to jaw muscle overgrowth, shorter legs, thicker tails, muscle cramps in shoulders and thighs. Normal lifespan if not euthanized, but structural abnormalities can affect quality of life.
• Heterozygotes (carriers): Increased muscle mass (approximately 5% more muscle), enhanced racing performance (documented competitive advantage), NO health issues. These dogs appear as exceptionally muscular, athletic Whippets.
• Normal (non-carriers): Typical Whippet musculature and performance

Breeding implications: This is the ONLY known condition in dogs where the heterozygous state confers a performance advantage with no health compromise. Many successful racing Whippets are carriers. However, breeding two carriers together produces a 25% risk of homozygous bully whippets. Testing both breeding partners allows informed decisions—a carrier can be safely bred to a non-carrier with zero risk of producing affected puppies.

Mitral Valve Disease (MVD/MMVD)

Prevalence: Moderate to common—the breed is overrepresented for MVD, described as "very prevalent" by the Whippet Health Foundation

Inheritance: Polygenic with genetic loci identified on chromosomes 15 and 2

DNA test available: NO (genetic basis known but complex inheritance; no single-gene test)

Clinical presentation: Heart murmur (auscultation finding), exercise intolerance, coughing, difficulty breathing, lethargy. Variable expressivity means some dogs develop severe disease at earlier ages than others. Age-related penetrance makes identifying true control dogs difficult—a dog clear at 5 years may develop MVD at 8 years.

Breeding implications: Cardiac echocardiography is ESSENTIAL for breeding stock and should be repeated every 2 years (or annually for high-risk lines). This is not a simple recessive—it shows complex inheritance with multiple contributing genes. Avoid breeding dogs with early-onset MVD (detected under 6 years). Dogs clear at advanced ages (8+ years) are valuable for reducing disease frequency. The genetic research is ongoing; breeders should stay current with Whippet Health Foundation updates.

Anesthesia Sensitivity (Sighthound-Specific)

Prevalence: Common to universal—95%+ of all sighthounds including Whippets carry the genetic mutation

Inheritance: Genetic mutation causing reduced CYP2B11 enzyme production (same mutation found in Greyhounds, Borzoi, Scottish Deerhounds, and Irish Wolfhounds)

DNA test available: YES (research test available; clinical testing emerging)

Clinical presentation: Prolonged and potentially life-threatening recovery from thiobarbiturate anesthetics (thiopental, thiamylal) and propofol due to slow metabolism. Sighthounds have very little body fat, so drugs remain in the bloodstream longer rather than being redistributed into fat stores. Recovery can take hours to days if inappropriate agents are used.

Critical veterinary guidance: Thiobarbiturates should be AVOIDED in all Whippets. Use alternative induction agents such as ketamine, etomidate, or propofol with extreme caution and reduced dosing. This is relevant for C-sections, dental procedures, and any anesthetized procedure. Ensure your veterinarian is aware of sighthound sensitivity BEFORE any procedure.

Breeding implications: This is essentially breed-universal and cannot be bred out. The focus is on education—ensure puppy buyers and veterinarians are aware of the sensitivity. Include anesthesia warnings in puppy contracts and health information packets.

Congenital Deafness (Pigment-Associated)

Prevalence: Low in the general breed population; higher in white and merle dogs. Single merles: 2.7% unilateral, 0.9% bilateral. Double merles: 10% unilateral, 15% bilateral deafness.

Inheritance: Polygenic, associated with lack of pigment cells (melanocytes) in the inner ear. Not a simple recessive—linked to white spotting and merle patterns.

DNA test available: NO (diagnosis via BAER testing only)

Clinical presentation: Unilateral (one ear) or bilateral (both ears) hearing loss present from birth. Unilaterally deaf dogs appear completely normal in behavior and cannot be detected without BAER testing. Bilaterally deaf dogs can be identified by lack of startle response to sound.

BAER testing essential: White on or near the ears is an indicator of potential lack of pigment in the inner ear. ALL breeding stock should be BAER tested regardless of color, as deafness can occur in any color but is more common with white/merle markings. Unilaterally deaf dogs should not be bred due to increased risk of producing bilateral deafness.

Progressive Retinal Atrophy (PRA)

Prevalence: Low to moderate in Whippets

Inheritance: Autosomal recessive (multiple forms exist)

DNA test available: YES for specific forms

Clinical presentation: Progressive vision loss beginning with night blindness, eventually leading to complete blindness. Retinal degeneration visible on CERF examination. Dilated pupils, reluctance to move in dim light. Typically develops between 3-7 years depending on type.

Breeding implications: Annual CERF eye exams detect PRA before clinical signs appear. DNA testing for known PRA mutations allows identification of carriers. Avoid breeding two carriers together.

Lens Luxation

Prevalence: Low to moderate

Inheritance: Autosomal recessive (primary form) or secondary to other eye conditions

DNA test available: YES for primary lens luxation

Clinical presentation: Displacement of lens from normal position within the eye, causing pain, redness, cloudiness, and vision loss. Can cause secondary glaucoma if untreated. Typically develops between 3-6 years.

Breeding implications: DNA testing identifies carriers of primary lens luxation. Do not breed two carriers together. CERF exams detect early lens instability.

Cryptorchidism (Undescended Testicles)

Prevalence: Low to moderate (approximately 8% in breed data; general population 7-10%)

Inheritance: Hereditary with genetic basis (specific genes not yet identified)

DNA test available: NO

Clinical presentation: One or both testicles fail to descend into the scrotum by 6-8 months of age. Affected dogs have a 13x higher risk of testicular cancer. Disqualification from conformation showing.

Breeding implications: Cryptorchid dogs should NEVER be bred. This is a hereditary condition with serious health and welfare implications. Both parents of a cryptorchid puppy are carriers and should be bred with caution (avoid breeding to dogs from lines with cryptorchidism history).

Hypothyroidism

Prevalence: Low to moderate

Inheritance: Polygenic/complex (may include autoimmune component)

DNA test available: NO (diagnosis via blood panel)

Clinical presentation: Weight gain, lethargy, poor coat quality, hair loss, skin infections, cold intolerance. Typically develops between 4-8 years.

Breeding implications: OFA thyroid panel provides baseline data. Dogs diagnosed with hypothyroidism can be managed medically but breeding value should be carefully evaluated as the condition is heritable.

Color and Coat Genetics

Whippets have one of the most permissive color standards in the AKC, stating that "any color" is acceptable with no color disqualifications. This provides breeders with exceptional freedom in color breeding programs while requiring careful management of health issues linked to certain color patterns.

AKC accepted colors include:

• Black
• White
• Red
• Fawn (ranging from pale cream to deep red)
• Blue (dilute black, slate gray appearance)
• Cream
• Brindle (in all color combinations)
• Particolor (any color with white markings)
• Solid colors
• Any mixture of colors

The standard explicitly states "any color or mixture of colors" is acceptable. There are NO color disqualifications in the Whippet breed standard based on color alone. The only disqualifications are structural (height variance >0.5 inch), eye-related (blue eyes, heterochromia), and bite-related (undershot, overshot >0.25 inch).

Relevant genetic loci:

• A (Agouti): Controls distribution of black and red pigment across the coat
• B (Brown): Affects eumelanin pigment (rare in Whippets—most are B/B black-based)
• D (Dilution): Creates blue (dilute black) and dilute fawn from black and red base colors
• E (Extension): Controls distribution of red/yellow pigment; determines whether a dog can express black pattern
• K (Dominant Black): Controls brindle patterning—kyky allows brindle expression
• S (Spotting): Controls white markings and piebald patterns (Irish spotting to extreme white)
• M (Merle): Creates merle pattern (documented in breed but associated with health concerns)

Color complexity tier: Medium. While breeders have exceptional freedom due to the "any color" acceptance, understanding color genetics is important for predicting color outcomes and managing health-linked color issues.

Health-linked color considerations:

Merle pattern (especially double merle/homozygous M/M):

• Single merles (M/m): 2.7% unilateral deafness, 0.9% bilateral deafness risk, plus increased risk of eye abnormalities (microphthalmia, colobomas)
• Double merles (M/M): 10% unilateral deafness, 15% bilateral deafness, plus significantly increased risk of severe eye defects

Breeding guidance: Merle to merle breeding is strongly discouraged due to high risk of double merle puppies with deafness and eye abnormalities. Merle to solid color breeding produces approximately 50% merle puppies with lower health risk. BAER test ALL white or merle breeding stock.

Extensive white markings (especially on head/ears):

• Associated with congenital deafness due to lack of pigment cells (melanocytes) in the inner ear. White on or near the ears is a warning sign of potential inner ear pigment deficiency.
• Unlike some breeds where white is restricted, the Whippet standard allows extreme white markings. However, these dogs carry increased deafness risk and MUST be BAER tested before breeding.

Blue dilute (d/d genotype):

• Potential for color dilution alopecia (dilute coat becomes thin, breaks easily, hair loss in patches). This is rare in Whippets compared to breeds like Dobermans, but it is documented.
• Dilute dogs can be bred safely but monitor coat quality. If alopecia develops, remove that dog and close relatives from breeding programs.

Color breeding strategy for responsible breeders:

Unlike breeds with color-linked disqualifications or show faults, Whippets offer complete freedom. However, health-first breeding means:

1. BAER test all breeding stock regardless of color (deafness can occur in any color but is higher risk with white/merle)
2. Avoid merle × merle breeding (double merle risk)
3. Prioritize dogs with proven hearing and vision over specific color goals
4. Monitor dilute coats for alopecia; discontinue breeding if coat quality is poor
5. The breed's "any color" acceptance makes it easier to prioritize health and structure over color—take advantage of this flexibility

Contrast this with more restrictive breeds like the Basenji, where specific color patterns are standard faults. The Whippet standard's color permissiveness allows breeders to focus on structure, health, and temperament as primary selection criteria.

Selecting Whippet Breeding Stock

Selecting Whippet breeding stock requires balancing multiple priorities: structural soundness for coursing function, health testing results, genetic diversity (managing COI), temperament, and adherence to the breed standard's strict height requirements. The breed's athletic heritage means running gear and gait are non-negotiable—beauty without function defeats the purpose.

Conformation priorities for breeding Whippets:

Shoulder and upper arm (critical for reach): Well laid-back shoulder (approximately 45-degree angle) with upper arm of equal length to shoulder blade. This creates the extended reach essential for coursing. Short or steep upper arms are serious faults that destroy forward reach and shorten stride. Examine angulation at a young age and reassess at maturity.

Depth of brisket: Chest must reach to the elbows, providing room for heart and lungs. This is not negotiable in a breed built for sustained speed. Shallow-chested dogs lack the cardiovascular capacity for work.

Strong, slightly arched loin: The loin provides driving power during the double-suspension gallop. It should show slight arch and be muscular without being long or soft. A long, weak loin loses power transmission from rear to front.

Rear angulation: Well-bent stifle and low-set hocks provide drive. Straight stifles reduce rear extension and stride length. The rear assembly must match the front angulation—balanced angulation front and rear produces the most efficient gait.

Head type and expression: Long, lean head with small rose ears (not prick or button ears) and keen, alert expression. Round or prominent eyes are incorrect and lose the breed's characteristic intensity. Avoid coarse or heavy heads.

Topline: Level from withers to loin with gentle arch over loin. Soft, sagging, or roached toplines are serious faults. The topline should remain firm and level during movement.

Height within standard (DQ concern): Males 19-22 inches, females 18-21 inches. More than 0.5 inch variance is an automatic disqualification. Measure at withers at 24+ months when structure is mature. Dogs measuring 22.6"+ (males) or 21.6"+ (females) cannot be bred or shown. Similarly, males under 18.5" or females under 17.5" are disqualified.

Bite and eye color (DQ concerns): Scissors bite is required. Undershot or overshot >0.25 inch is disqualified. Eyes must be dark and matching—blue eyes or heterochromia (different colored eyes) are disqualified. Check eye color at 8 weeks and confirm at 6-8 months as eye color can change during maturation.

Gait (THE defining characteristic): Powerful, ground-covering movement with excellent reach and drive. The Whippet should move effortlessly at speed, showing true double-suspension gallop. Poor reach, restricted drive, short-strided movement, or lack of flexibility are deal-breakers. Video dogs free-coursing to assess true movement ability beyond the show ring.

Common faults to select against:

• Short or steep upper arm (destroys reach)
• Straight, upright shoulder
• Elbows turning out or in
• Weak or broken-down pasterns
• Shallow chest with poor heart room
• Long, soft, or roached topline
• Flat or steep croup
• Straight stifle (reduces drive)
• Cow hocks or sickle hocks
• Small, light bone for body size
• Coarse, heavy head
• Round or prominent eyes
• Overshot or undershot bites
• Restricted movement, short stride, poor gait efficiency
• Height variance approaching DQ range

Temperament evaluation:

Whippets should be amiable, friendly, gentle, and non-aggressive. They are typically quiet and dignified indoors but become intensely focused and driven during coursing or play. Evaluate breeding stock for:

• Stable, confident temperament with appropriate prey drive for lure coursing but good "off-switch" indoors
• Avoidance of extreme shyness, nervousness, or aggression
• Tolerance for handling during showing and veterinary exams without stress
• Good interactions with other dogs (Whippets are generally social and friendly)
• Response to novel stimuli (should be curious but not fearful)
• Strong coursing instinct and desire to chase (essential breed characteristic) but controllable when asked

Temperament testing in puppies at 7-8 weeks identifies stable, confident individuals for breeding and performance homes.

Genetic diversity and COI management:

Average breed COI: 7% (10-generation calculation)

Target COI for breeding decisions: Under 5% (5-generation preferred, 10-generation ideal)

Whippets have a relatively healthy genetic diversity compared to some purebred populations, but managing COI remains important for long-term breed health. Calculate COI for all potential breedings and favor pairings that reduce inbreeding. The breed's moderate population size and active international breeding allow outcrossing to reduce COI without sacrificing type.

Health testing requirements for breeding stock:

Before breeding any Whippet, complete all CHIC-required tests:

• CAER eye examination (annual; current within 12 months)
• Cardiac echocardiogram (minimum every 2 years; annual preferred)
• BAER hearing test (one-time; must show bilateral hearing)

Strongly recommended:

• Myostatin DNA test (know carrier status; avoid carrier × carrier breedings)
• OFA hips (baseline data, especially for performance lines)
• OFA thyroid panel (baseline fertility and health data)
• DNA tests for PRA and lens luxation if available for breed

Never breed:

• Dogs with blue eyes or heterochromia (DQ)
• Dogs with height variance >0.5 inch above/below standard (DQ)
• Dogs with undershot bite or overshot >0.25 inch (DQ)
• Unilaterally or bilaterally deaf dogs (BAER test required)
• Cryptorchid males (hereditary condition with cancer risk)
• Dogs with early-onset mitral valve disease (detected under 6 years)
• Dogs with poor coursing ability or restricted gait (defeats breed purpose)

Stud dog selection:

Stud fee range: $800-$1,500 depending on dog's accomplishments, health testing, and proven production record

When selecting a stud dog, prioritize:

• Complementary structure (strengthen bitch's weaknesses without overcorrecting)
• Complete health testing with excellent cardiac evaluation results
• Proven ability to produce puppies with correct structure and temperament
• Low COI when bred to your bitch (ideally under 5%)
• BAER tested with bilateral hearing
• Known myostatin status (if bitch is carrier, select non-carrier stud)
• Performance or show record demonstrating coursing ability and correct movement

Many top breeders offer stud service to approved bitches only after reviewing pedigree, health testing, and structure. Expect to provide full health documentation for your bitch.

Whelping and Neonatal Care

Whippets are generally trouble-free whelpers due to their medium size, athletic build, and moderate puppy size relative to the dam's pelvic capacity. Natural whelping is the norm and should be expected with proper prenatal care and monitoring.

Whelping method: Natural whelping in approximately 90% of litters. The 10% C-section rate is significantly lower than brachycephalic breeds but can occur with very large litters (9-10 puppies), uterine inertia in older dams, or singleton puppies (single puppy can grow large and cause dystocia).

CRITICAL anesthesia sensitivity: If a C-section is required, ensure your veterinarian is aware of sighthound anesthesia sensitivity. Thiobarbiturates (thiopental, thiamylal) must be AVOIDED. Use alternative induction agents such as ketamine, etomidate, or propofol with reduced dosing and veterinary awareness of prolonged recovery times. Plan C-section protocols with your veterinarian BEFORE the due date so appropriate anesthetic agents are available. Recovery from anesthesia can take hours to days if inappropriate agents are used—this is a life-threatening risk.

Breed-specific whelping considerations:

Low body fat: Whippets have minimal body fat, which affects thermoregulation during and after whelping. Provide supplemental heating with whelping box heating pads or heat lamps to maintain ambient temperature of 85-90°F for the first week. Dams may become chilled during whelping—monitor dam temperature and provide blankets or heat sources as needed.

Variable litter sizes: Litter size ranges from 1 to 10 puppies. Very small litters (1-2 puppies) may experience difficult whelping because puppies grow larger. Very large litters (9-10 puppies) may cause uterine crowding and inertia. Monitor all litters carefully regardless of size.

Uterine inertia risk: Older dams (6+ years) or very large litters may experience primary or secondary uterine inertia. Have oxytocin on hand and veterinary contact numbers ready. If contractions stop for more than 2 hours between puppies, contact your veterinarian.

Lean body condition essential: Throughout pregnancy, maintain the dam's athletic body condition. Overweight dams face increased whelping complications despite the breed's easy-whelping reputation. You should be able to feel ribs easily with gentle pressure throughout pregnancy.

Birth weight and neonatal monitoring:

Average birth weight:

Males: 10-12 ounces (0.625-0.75 pounds)

Females: 8-10 ounces (0.5-0.625 pounds)

Daily weight gain target: Puppies should double their birth weight by day 7-10, then gain approximately 5-10% of body weight daily. Expect 1-2 ounces per day gain in the first weeks. Weigh puppies daily on a gram scale to track weight gain. Any puppy losing weight or failing to gain requires immediate attention (supplemental feeding, veterinary evaluation for cleft palate or other issues).

Neonatal care protocol:

Days 1-3: Check puppies every 2-3 hours. Ensure all puppies are nursing vigorously and gaining weight. Provide supplemental heating (whelping box temperature 85-90°F). Monitor for fading puppy syndrome—puppies that become cold, stop nursing, or cry continuously require immediate intervention.

Days 4-14: Continue daily weighing. Whelping box temperature can be gradually reduced to 80°F by day 7 and 75°F by day 14 as puppies develop better thermoregulation. Monitor for congenital issues (cleft palate, swimmers, hernias). All puppies should be active, nursing well, and gaining weight consistently.

Weeks 3-4: Eyes open around day 10-14, ears open around day 14-21. Puppies become mobile and begin eating soft food. Start weaning process with gruel (puppy kibble soaked in goat milk or puppy formula).

Dewclaw, tail, and ear practices:

Dewclaw removal: NOT performed in Whippets. Front dewclaws remain (all breeds have them). Rear dewclaws are uncommon in Whippets but if present, removal is optional and NOT required by the standard.

Tail docking: NOT performed. Whippets have natural long tails that taper to a point. The tail is essential for balance during high-speed coursing.

Ear cropping: NOT performed. Whippets have natural rose ears. Any surgical alteration is against the breed standard.

Puppy vet check timing:

Schedule initial vet check at 2-3 days of age to examine for congenital defects, check palates, assess hernias, and confirm overall health. Follow-up exams occur at 6-8 weeks before puppies go home, including first vaccinations and deworming.

Puppy Development Milestones

Whippet puppies develop rapidly in the first 12 weeks, with critical socialization windows and structural evaluation timing that determines show potential versus pet placement.

Weekly development milestones:

Weeks 0-2 (neonatal period):

• Birth weight: 8-12 ounces (females smaller than males)
• Eyes and ears closed
• Cannot regulate body temperature (require supplemental heat)
• Entirely dependent on dam for nutrition and elimination
• Should double birth weight by day 7-10
• Daily weight gain: 1-2 ounces per day

Weeks 3-4 (transitional period):

• Eyes open around day 10-14
• Ears open around day 14-21
• Begin walking (wobbly at first)
• Start weaning process with puppy gruel (soaked kibble in goat milk or formula)
• First teeth emerge around day 21
• Begin eliminating away from sleeping area
• Weight: 3.5-4.8 pounds by week 4

Weeks 5-7 (critical socialization window begins):

• Socialization window: 3-14 weeks is the CRITICAL period for socialization exposure. Puppies should meet various people, hear different sounds, walk on different surfaces, and experience gentle novel stimuli.
• Fully mobile, running, playing with littermates
• Learning bite inhibition through play
• Dam begins disciplining puppies (teaching manners)
• Fully weaned by 6-7 weeks
• Can begin basic house training (take puppies outside after eating/sleeping)
• Weight: 6-8.8 pounds by week 7

Week 8 (go-home age for pet puppies):

• Minimum go-home age: 8 weeks per most state laws
• First vaccinations (6-8 weeks): DA2PP (distemper, adenovirus, parvovirus, parainfluenza)
• Deworming completed (2, 4, 6, 8 weeks)
• Microchipping completed
• Weight: 8.5-10 pounds
• Fully socialized to humans, comfortable with handling
• Eating solid puppy kibble (3-4 meals per day)

Early structural evaluation (8 weeks):

At 8 weeks, experienced breeders can perform an initial structural evaluation to identify potential show prospects versus pet-quality puppies. Evaluate:

• Overall balance and proportions
• Head type and expression
• Bite (should be scissors at this age)
• Eye color (should be darkening; blue at 8 weeks may stay blue—DQ concern)
• Front and rear angulation
• Topline (should be level with slight arch developing over loin)
• Movement (free-stack and gait the puppy; look for smooth, balanced movement)
• Temperament and confidence

NOTE: Show prospects should be held until 10-12 weeks for more accurate structural assessment. Puppy proportions change dramatically between 8-12 weeks.

Weeks 10-12 (ideal go-home age for show prospects):

• Re-evaluate structure at 10 weeks and again at 12 weeks
• Proportions stabilize enough to make show vs. pet decisions
• Flight period begins around 8-10 weeks (puppies may become cautious; continue socialization but don't overwhelm)
• Weight: 13-15 pounds by 12 weeks
• Ready for performance/show homes with experienced handlers

Months 4-8 (adolescence/gangly phase):

• Rapid growth phase
• Puppies go through awkward stages (growth spurts cause temporary imbalance)
• Structure fluctuates—don't make final show decisions during this phase
• Second fear period around 6-8 months (continue positive socialization)
• Adult teeth fully in by 6-7 months
• Re-evaluate bites at 6 months (some bites deteriorate during teething)
• Males: height approaching adult size (within 1-2 inches of adult)
• Females: may have first heat between 6-12 months (typically later in Whippets)

Months 9-14 (young adult):

• Approaching adult size and proportions
• Height stabilizes around 12-14 months
• Males may continue filling out (adding muscle and substance) until 18 months
• Final structural evaluation: Re-assess at 12 months and 18 months
• This is when you can definitively determine if a dog meets the height standard (19-22" males, 18-21" females) or is approaching DQ range
• Measure height carefully at 12 months and 18 months—any dog approaching DQ variance (22.6"+ males, 21.6"+ females or under 18.5" males, 17.5" females) should not be bred or shown

Adult size achievement: 12-14 months for height; 18 months for full muscular development and substance. Some males may continue to add muscle and "finish" until 24 months but should not gain significant height after 14 months.

Socialization window and prey drive management:

The 3-14 week socialization period is CRITICAL in Whippets. Expose puppies to:

• Various people (different ages, genders, appearances)
• Other dogs (vaccinated, healthy, friendly)
• Different surfaces (grass, concrete, gravel, tile, carpet)
• Common sounds (vacuum, doorbell, TV, car rides)
• Gentle novel stimuli (umbrellas, bicycles, strollers)

IMPORTANT: Simultaneously respect the Whippet's strong prey drive. Early exposure helps puppies learn to differentiate between prey (appropriate to chase) and family pets (not prey). However, recognize that the prey drive is hardwired—even well-socialized Whippets may chase cats, squirrels, or small animals. Manage the environment rather than expecting to eliminate the drive.

Go-home age recommendations:

Pet puppies: 8 weeks minimum

Show prospects: 10-12 weeks preferred (allows more accurate structural assessment)

Some breeders hold show prospects until 6-8 months to definitively assess structure during the gangly phase, but most show prospects go at 10-12 weeks to experienced show homes that understand structural development.

Breeding Economics

Breeding Whippets responsibly is a significant financial investment. While the breed's low C-section rate (10%) and moderate litter size (6 puppies average) reduce some costs compared to high-risk breeds, comprehensive health testing and quality prenatal care ensure expenses are substantial.

Complete cost breakdown for one litter (natural whelping):

Health testing (dam, one-time or recurring):

• BAER hearing test (one-time): $215
• CAER eye exam (annual): $100
• Cardiac echocardiogram (every 2 years): $515 (prorated to $257.50 per year or ~$43 per litter if breeding annually)
• Optional: Myostatin DNA test: $65
• Optional: OFA hips: $150
• Optional: Thyroid panel: $130
• Total per breeding cycle: Approximately $830 for full CHIC requirements

Breeding and prenatal costs:

• Stud fee: $800-$1,500 (average $1,000)
• Progesterone testing (3-4 tests to determine optimal breeding day): $240 ($60 × 4 tests)
• Prenatal veterinary care (2-3 exams, ultrasound confirmation): $350
• Subtotal breeding/prenatal: $1,590

Whelping costs (natural):

• Whelping supplies (pads, towels, heating pad, scale, emergency supplies): $200
• Veterinary supervision (if needed): $0-$500 (assuming natural whelping without complications)
• Average natural whelping cost: $200

Whelping costs (C-section if needed—10% of litters):

• Emergency or planned C-section: $2,000-$3,000 (average $2,500)
• Remember: Whippets require sighthound-safe anesthesia protocols (avoid thiobarbiturates)

Puppy care costs (birth to 8 weeks, 6 puppies):

• Veterinary exams (2-3 visits for litter): $150
• First vaccinations (6 puppies @ $25-$35 each): $180
• Deworming (4 rounds for 6 puppies): $60
• Microchipping (6 puppies @ $25-$50 each): included in vet visit typically
• Puppy food (dam and puppies through 8 weeks): $400
• AKC litter registration + individual puppy registrations: $180
• Total puppy care: Approximately $970 (calculated as $390 vet + $400 food + $180 registration)

Marketing and miscellaneous:

• Website updates, photos, advertising: $100-$300
• Puppy starter kits (collar, leash, food sample, health records, toy): $50-$75 per puppy = $300-$450 for 6 puppies
• Estimated marketing/misc: $400-$750

TOTAL COST PER LITTER (natural whelping):

• Health testing: $830
• Stud fee: $1,000
• Progesterone testing: $240
• Prenatal care: $350
• Whelping: $200
• Puppy vet/registration: $970
• Food and supplies: $400
• Marketing/starter kits: $400
• TOTAL: $4,390 (rounded from $4,390)

TOTAL COST PER LITTER (C-section):

Replace $200 natural whelping cost with $2,500 C-section cost = $6,690

Revenue:

Average puppy price:

Pet quality: $1,200

Show quality: $2,000

Average litter revenue (6 puppies, mix of pet and show quality): Assuming 4 pet-quality puppies at $1,200 and 2 show-quality puppies at $2,000 = $8,800 potential revenue. However, many litters are priced uniformly at $1,200 per puppy = $7,200 revenue for 6 puppies.

Net financial analysis:

Natural whelping:

Revenue: $7,200 (6 puppies @ $1,200)

Costs: $4,390

Net: +$2,810 per litter

C-section whelping (10% of litters):

Revenue: $7,200

Costs: $6,690

Net: +$510 per litter

Is breeding Whippets profitable?

On paper, a natural whelping with average litter size yields a modest profit of approximately $2,800. However, this calculation does NOT include:

• Time investment (hundreds of hours for prenatal care, whelping, puppy raising, socialization, buyer screening, lifetime support)
• Facility costs (whelping room, fencing, kennels)
• Show/performance expenses to prove breeding stock (entry fees, travel, handler fees)
• Health testing for the STUD DOG (if you own him—add another $830)
• Recurring costs (annual CERF exams, biennial cardiac echoes over the dam's breeding career)
• Emergency veterinary care (not all whelps are complication-free)
• Smaller litters than average (break-even occurs around 4-5 puppies depending on pricing)

Financial reality: Responsible Whippet breeding is rarely profitable when ALL costs are accounted for. Breeders who prioritize health testing, proper socialization, lifetime support, and quality puppy placement often break even or lose money per litter. The "profit" is seeing healthy, sound Whippets in loving homes and contributing to breed preservation—not financial gain.

Puppy pricing considerations:

Pricing should reflect:

• Comprehensive health testing of both parents
• Quality of pedigree and accomplishments (championships, performance titles)
• Level of socialization and puppy-raising protocols
• Lifetime breeder support and health guarantees
• Regional market (prices vary by location and demand)

Underpricing puppies attracts the wrong buyers (people looking for a bargain rather than a quality Whippet). Overpricing without corresponding quality damages your breeding reputation. Research regional pricing and price competitively based on the quality you produce.

Breeder Resources

Responsible Whippet breeders have access to extensive resources through the parent club, regional organizations, and online communities focused on health research and breed education.

Parent Club:

American Whippet Club (AWC)

Website: https://www.americanwhippetclub.org/

The AWC is the AKC-recognized parent club for Whippets and offers:

• Breeder referral directory
• Breeder education programs and mentorship
• Code of Ethics for member breeders
• Health and genetics resources
• National specialty shows and performance events
• Judges education
• Rescue network

Membership in the parent club provides access to experienced breeder mentors, health research updates, and a network of breeders committed to maintaining breed quality and health.

Health Research Organization:

Whippet Health Foundation (WHF)

Website: https://www.whippethealth.org/

The WHF funds research into hereditary health conditions affecting Whippets and provides:

• Health survey data
• Research updates on mitral valve disease, myostatin mutation, and other conditions
• Educational resources for breeders
• Contribution opportunities to fund health research

AKC Breeder Programs:

AKC Breeder of Merit

Requirements include:

• Minimum 4 AKC titles on dogs bred/owned
• 5+ years breeding experience
• All dogs health tested per CHIC requirements
• Commitment to AKC Code of Conduct

Benefits: Recognition as a dedicated breeder, inclusion in AKC Breeder of Merit directory, marketing tools.

AKC Bred with H.E.A.R.T.

Requirements include:

• Health testing (CHIC requirements met)
• Education (completed breeder education courses)
• Accountability (inspectable records)
• Responsibility (lifetime commitment to puppies)
• Tradition (participation in AKC events)

Benefits: Public recognition, marketing materials, access to exclusive resources.

Recommended Reading:

• The Complete Whippet by Bo Bengtson (comprehensive breed history, structure, breeding)
• The Whippet by Catherine G. Sutton (breed standard interpretation, breeding practices)
• Whippets Today by Lilian Sawyer (modern breeding practices and health information)
• AWC Breeders Education Guide (available through American Whippet Club membership)

Online Communities:

• American Whippet Club member directory and forums
• Whippet Health Foundation website and mailing lists
• WhippetCentral.com (breed enthusiast community)
• Facebook groups: "Whippet Breeders" (private group for verified breeders), "Whippet Owners Group" (public community)
• Performance and lure coursing groups (AKC lure coursing, ASFA coursing)

Regional Whippet Clubs:

Many regions have local Whippet clubs offering:

• Local specialty shows
• Lure coursing and performance events
• Breeder networking
• Educational seminars
• Puppy buyer referrals

Check the American Whippet Club website for regional club listings and contact information.

Mentorship:

New breeders are strongly encouraged to seek mentorship from established AWC members. A mentor can provide:

• Guidance on selecting breeding stock
• Whelping support and advice
• Structural evaluation of puppies
• Buyer screening assistance
• Lifelong support as your breeding program develops

The American Whippet Club offers formal mentorship programs connecting new breeders with experienced members.

Frequently Asked Questions

How many puppies do Whippets typically have?

Whippets average 6 puppies per litter, with a normal range of 1 to 10 puppies. The most common litter sizes are 5-7 puppies (approximately 60% of litters fall in this range). Very small litters (1-2 puppies) occur in about 8% of breedings and may result in larger individual puppy size and potential dystocia. Large litters (9-10 puppies) occur in about 4% of breedings and may increase the risk of uterine inertia or require supplemental feeding if the dam cannot adequately nurse all puppies.

Do Whippets need C-sections?

No, Whippets typically whelp naturally and have a low C-section rate of approximately 10%. This is significantly lower than many other breeds due to the Whippet's medium size, athletic build, and moderate puppy size relative to the dam's pelvic capacity. C-sections may be required for very large litters (9-10 puppies), uterine inertia in older dams, or singleton puppies that grow too large. If a C-section is needed, it is CRITICAL that your veterinarian uses sighthound-safe anesthesia protocols—avoid thiobarbiturates and use alternative agents like ketamine or etomidate. Plan protocols with your vet before the due date.

What health tests are required for breeding Whippets?

The American Whippet Club's CHIC requirements mandate three tests: (1) CAER eye examination (annual), (2) Cardiac echocardiogram screening for mitral valve disease (minimum every 2 years), and (3) BAER hearing test (one-time) to detect congenital deafness. Total baseline cost is approximately $830. Additionally, many breeders perform the myostatin DNA test ($65) to identify carriers of the Bully Whippet mutation, OFA hip evaluation ($150), and thyroid panel ($130). All breeding stock should be BAER tested regardless of color due to deafness risk, particularly in white or merle dogs.

How much does it cost to breed Whippets?

A typical Whippet litter with natural whelping costs approximately $4,390 including health testing ($830), stud fee ($1,000), progesterone testing ($240), prenatal care ($350), whelping supplies ($200), puppy veterinary care and registration ($970), food ($400), and marketing/starter kits ($400). If a C-section is required (10% of litters), costs increase to approximately $6,690. These figures do not include time investment, facility costs, show expenses, or the stud dog's health testing if you own him. Responsible breeding rarely generates significant profit when all costs are included.

At what age can you breed a Whippet?

Females should be at least 24 months (2 years) old before breeding to allow completion of all health testing, particularly the OFA cardiac evaluation which requires a minimum age of 24 months. Most Whippet bitches do not have their first heat until 12-24 months (some as late as 3+ years), so breeding at 24 months typically occurs on the second or third heat. Males can be used for stud service at 12-18 months once health testing is complete, though many breeders wait until males prove themselves in performance events or show competition before standing them at stud.

How much do Whippet puppies cost?

Pet-quality Whippet puppies from health-tested parents typically cost $1,200-$1,500. Show-quality puppies with exceptional structure and pedigree may cost $2,000-$2,500. Prices vary by region, breeder reputation, and the accomplishments of the parents (championships, performance titles, health clearances). Puppies from breeders who perform comprehensive health testing, provide extensive socialization, and offer lifetime support are priced at the higher end of the range. Be wary of significantly lower prices, which may indicate lack of health testing or poor breeding practices.

What are the most common health problems in Whippets?

The most significant health concerns in Whippets are: (1) Mitral valve disease (MVD)—overrepresented in the breed with genetic basis on chromosome 15, requiring cardiac screening; (2) Anesthesia sensitivity—95%+ of Whippets carry the sighthound mutation causing prolonged recovery from certain anesthetics; (3) Congenital deafness—particularly in white or merle dogs, requiring BAER testing; (4) Myostatin deficiency (Bully Whippet syndrome)—carriers show enhanced racing performance but breeding two carriers risks producing affected puppies; (5) Progressive retinal atrophy (PRA) and lens luxation affecting vision; and (6) Hypothyroidism. Responsible breeders screen for these conditions through cardiac echocardiography, BAER testing, annual eye exams, and DNA testing.

Is breeding Whippets profitable?

Responsible Whippet breeding is rarely profitable when all costs are accounted for. A natural whelping with average litter size (6 puppies) generates approximately $7,200 revenue at $1,200 per puppy, with costs around $4,390, yielding a $2,810 profit on paper. However, this does not include time investment (hundreds of hours), facility costs, show/performance expenses to prove breeding stock, recurring health testing over multiple years, emergency veterinary care, or smaller-than-average litters. When these are factored in, most responsible breeders break even or lose money. The motivation should be breed preservation and producing healthy, sound Whippets—not financial gain.

What is the myostatin mutation in Whippets?

The myostatin mutation in Whippets causes two distinct phenotypes depending on the genotype. Heterozygous carriers (one copy of the mutation) have approximately 5% more muscle mass and show documented enhanced racing performance with NO health issues—this is the only known canine condition where carriers have a performance advantage. Homozygous affected dogs (two copies of the mutation) are called "bully whippets" and show extreme muscular hypertrophy from birth, broader heads, pronounced overbites, shorter legs, muscle cramps, and structural abnormalities. DNA testing allows breeders to identify carriers and avoid carrier × carrier breedings that produce a 25% risk of bully whippets.

Do all Whippets have anesthesia sensitivity?

Yes, essentially all Whippets (95%+ of sighthounds) carry the genetic mutation causing reduced CYP2B11 enzyme production, which results in slow metabolism of certain anesthetic drugs. This is a sighthound-universal trait shared with Greyhounds, Borzoi, Irish Wolfhounds, and Scottish Deerhounds. Whippets have prolonged and potentially life-threatening recovery from thiobarbiturates (thiopental, thiamylal) and require careful dosing of propofol. Alternative agents like ketamine or etomidate are safer options. This sensitivity cannot be bred out—it is part of the sighthound genetic makeup. Ensure all veterinarians treating your Whippets are aware of this sensitivity before any anesthetized procedure.

Are white Whippets more likely to be deaf?

Yes, white markings (particularly on or near the ears) are associated with increased risk of congenital deafness due to lack of pigment cells (melanocytes) in the inner ear. Whippets with extensive white markings have higher deafness risk than solid-colored dogs. Additionally, merle Whippets face increased deafness risk: single merles show 2.7% unilateral and 0.9% bilateral deafness, while double merles show 10% unilateral and 15% bilateral deafness. BAER testing is ESSENTIAL for all breeding stock regardless of color, as unilaterally deaf dogs appear behaviorally normal but carry increased risk of producing bilaterally deaf puppies. Do not breed any dog with unilateral or bilateral deafness.

Can I breed a Whippet that is slightly oversized?

No. The Whippet breed standard includes an absolute disqualification for height variance of more than one-half inch above or below the stated limits. Males must measure 19-22 inches at the withers, and females 18-21 inches. Any male over 22.5 inches or under 18.5 inches is disqualified, as is any female over 21.5 inches or under 17.5 inches. Disqualified dogs cannot be shown in conformation and should NOT be bred, as height is heritable and breeding oversized or undersized dogs perpetuates the problem. Measure breeding stock carefully at 24+ months when structure is mature. Correct height is a critical aspect of breed type and function.