Noise reactivity and fear of fireworks in dogs : a study of genetic and phenotypic variables

Abstract

Noise reactivity is one of the most common behavioral problems in dogs. Even though various studies find significant differences in prevalence between breeds, and some also find gender differences, noise reactivity seems to occur in all types of dogs. Dogs may react to everyday noises such as clattering from kitchen utensils or vacuum cleaners, roaring traffic, and construction work, but also weather phenomena such as thunder and wind, or the noise of fireworks and gunshots. Owners often state that it is the sharp, sudden noises that dogs react to, and fear of fireworks, in particular, is a well-known and frequently discussed topic among dog owners. Fear of loud noises and fireworks are probably influenced both by complex genetics and environmental factors.

This thesis deals with the genetic background of fear of fireworks and noise reactivity in dogs, with a particular focus on the standard poodle breed. A series of surveys have been carried out where dog owners have classified the level of noise reactivity in their dogs. Two questionnaires were aimed at owners of standard poodles or Irish soft-coated wheaten terriers, while the others were aimed at only owners of standard poodles. One epidemiological study, one pedigree-based heritability study, and one heritability study based on genetic association have been carried out.

The surveys show that 49.4% of standard poodles and 53.6% of Irish soft-coated wheaten terriers display weak to extremely strong fear of fireworks and/or loud noises. It was also found that the dogs with a stronger degree of fear showed more and stronger fear-related behaviors. The two breeds also express a somewhat different frequency of fear-related behaviors when they experience a noise-related fearful situation. Repeated evaluations of many dogs show that owners are consistent in their assessment of the noise reactivity of their dogs and that there is a correlation between noise reactivity and the number of displayed fear behaviors.

It was found that Irish soft-coated wheaten terriers have a slightly higher prevalence of noise reactivity and firework fear than standard poodles, and that older dogs are more fearful than younger dogs. Most dogs that show signs of noise reactivity display symptoms before the age of 4, but the degree of fear can worsen later in the dog's life. The study also shows that the most fearful dogs are more nervous in general, and that dogs that are the only dog in the household are more fearful than dogs that are accompanied by another dog.

Estimated heritabilities in the pedigree-based study are 0.09-0.16 for fear of fireworks and 0.13-0.16 for fear of loud noise, with a high positive correlation between the two traits. The heritability estimates in this study indicate that fear of fireworks and loud noises has significant genetic components, even if the pedigreebased heritability estimates are relatively low.

DNA samples from 400 standard poodles were analyzed to estimate genomic heritabilities and detect SNPs that may be associated with fear of fireworks or noise reactivity. Genomic heritabilities were calculated to be 0.28 for fear of fireworks and 0.15 for noise reactivity, with a strong genetic correlation between the two traits. Genome-wide association identified one region on chromosome 17, which shows a possible association, and this region harbors genes that may be of interest. More extensive studies with higher sample sizes will be needed to verify the study. This study found that there is a significant genetic component to fear of fireworks and loud noises and that these two complex genetic traits are strongly correlated. This study did not identify specific genes or gene variants that play a significant role in the development of a dog's fear of fireworks and loud noises. The estimated heritability of both fear of fireworks and fear of loud noises indicate that it should be possible to reduce the prevalence of these traits using selective breeding.

Ett av de vanligste atferdsproblemene hos hund er frykt for lyd. Ulike undersøkelser finner store raseforskjeller, og noen også kjønnsforskjeller, men frykt for lyd synes å forekomme hos alle typer hunder. Hunder kan reagere på hverdagslyder som gryteskrammel og støvsugere, trafikk og anleggsarbeider, men også værfenomen som torden og vind, eller lyden av fyrverkeri og skudd. Eiere opplyser oftest at det er de skarpe, plutselige lydene hundene reagerer mest på, og spesielt frykt for fyrverkeri er et velkjent og hyppig diskutert tema blant hundeeiere. Frykt for fyrverkeri og lyd er trolig komplekse genetiske egenskaper som i stor grad er påvirket av ulike miljøfaktorer. Denne avhandlingen ser nærmere på de genetiske årsakene til frykt for fyrverkeri og høy lyd hos hund, med et spesielt fokus på rasen storpuddel. Det er gjennomført en serie spørreundersøkelser der hundeeiere har klassifisert hundene sine når det gjelder graden av frykt for ulike høye lyder. To av undersøkelsene er rettet mot eiere av storpuddel og Irish softcoated wheaten terriere, mens de øvrige kun er rettet mot eiere av storpuddel. Det er gjennomført ett epidemiologisk studie, ett arvegradsstudie basert på stamtavle, og et genomisk assosiasjonsstudium der målet var å beregne genomisk arvegrader og forsøke å identifisere kromosomale regioner assosiert med frykt for høye lyder.