Genetic Mapping of Canine Fear and Aggression

In this study, fear and aggression traits were found and mapped on the dog genome. Previously, only certain physiological traits had been mapped in this way, but this concept has not before been used for behavioral traits. Three breed-specific resources were used: C-BARQ data and two genotype datasets. The design of the experiment included: principle components analysis (PCA) of breed phenotypes and genotypes from all three resources; a discovery study of GWA mapping of published C-BARQ behavioral data with one dataset; and a third confirmation/replication study of the previous using the second set of data.

First, from their PCA analysis of behavioral traits, the authors noticed that stranger-oriented fear, stranger-directed aggression and dog-directed aggression were cloistered together away from others and therefore could be related and might share the same loci. Then went on to analyze the first of their two genome data sets to find that those three traits are associated with two loci: chr18:23,260,370 and chrX:105,245,495-105,877,339. Dog-oriented fear was also found on chr18 and chrX. The data from the second set confirmed that chr18 and X were associated with stranger and dog-oriented aggression. The most similar results between the two studies were for dog-oriented fear (ch18, X), separation anxiety (ch10, X), and touch sensitivity (Ch10,18).

Haplotype analysis showed that the Dachshund and Yorkshire Terrier had much larger haplotypes for increased aggression compared to the alternative allele. The authors then stated that there was evidence of recent selection for the chr18 increased-fear/aggression haplotype in Dachshunds and Yorkshire Terriers; that selection is presumed to be for short legs in Dachshunds. The also found a linkage disequilibrium (LD) between size and aggression. In other words, small size and aggressive personalities are linked. Notably, owner-directed aggression and dog rivalry are associated with the same variation in IGF1 that is known to have the greatest contribution to small-size across dog breeds. They also stated that “some breeds, such as the Dachshund, contain the short legs mutation and the nearby increased-fear/aggression variation in the same haplotype”. However, the correlation between small dogs and aggression could be because aggression in large dogs is generally unacceptable to humans, and was therefore bred out.

Just like any study, this one can have its biases. And while it suggests that dachshunds can be aggressive, it is also important to remember that a dog’s behavior relies more upon their training than their traits.

Zapata, Isain, James A. Serpell, Carlos E. Alvarez. 2016. “Genetic mapping of canine fear and aggression”. BMC Genomics. Volume 17: 572.

Reviewed by: Anna Day