Epsilon Archive for Student Projects

Abstract

Both genetic and environmental factors are contributing to phenotypic variation. Early environmental factors play a crucial role in the development of behavior in dogs. Ethical and sustanible breeding requires carefully considered breeding decisions to prevent behavior problems such as fear and aggression. Litter size has been proposed as a potential environmental factor in previous research. The aim of this study was to investigate the association between litter size and the behavioral traits sociability and fearfulness (measured as environmental confidence) in the dog breed Cane Corso in Sweden. The analysise was based on data from the Swedish Kennel Club. The measured behavioral traits were variables included in the standardized behavioral test Behavior and Personality Assessment in Dogs (BPH). The study included 618 Cane Corso dogs registered in the Swedish Kennel Club.
Behavioral variables were standardized and analyzed using linear mixed models, with litter size included as a fixed effect and litter identity as a random effect to account for similarities among littermates. In an initial model without the random effect, litter size showed a significant association with sociability (p = 0.015). When litter identity was included, the effect of litter size was no longer significant. However variance component analysis indicated that about 17% of the total variation in sociability could be accounted for differences between litters. The initial analyse showed no significant association between litter size and environmental confidence. Pairwise comparisons between combined groups (≤ 5, 6-8 and ≥ 9) also failed to demonstrate a statistically significant difference. Although a tendency was observed for dogs from larger litters to exhibit lower environmental confidence compared to dogs from smaller litters (p = 0.08).
Overall, the results suggest that the observed effect of litter size reflects underlying litter specific factors rather than a direct effect of litter size in itself. The findings suggest that early shared litter effects may play an important role in shaping dog behavior such as sociability. For future research it would be desirable to include other dog breeds. This could provide a better understanding if the litter size effect differs between breeds. To include additional traits like aggression would also be of interest for a deeper understanding of the relationship between litter size and behavior developement.