Biology subjects

van der Bijl, W.

Publications and source records attributed to van der Bijl, W..

3 recordsLinked to original sources

bioRxiv2018

Dogs, but not wolves, lose their sensitivity towards novelty with age

Selection on behavioural traits holds a prominent role in the domestication of animals, with reductions in fear behaviour considered to be a key component. Specifically, there is a general assumption that domesticated species express reduced fear and reactivity towards novel stimuli compared to their ancestral species. However, very few studies have explicitly tested this proposed link between domestication and reduced fear responses. Of the limited number of studies experimentally addressing the alterations of fear during domestication, the majority have been done on canids. Previous work in foxes, wolves and dogs has led to the suggestion that decreased expression of fear in domesticated animals is linked to a domestication driven delay in the first onset of fearful behaviour during early ontogeny. Thus, wolves are expected to express exaggerated fearfulness earlier during ontogeny compared to dogs. However, while adult dogs are less fearful towards novelty than adult wolves and wolf-dog hybrids, consensus is lacking on when differences in fear expression arise in wolves and dogs. Here we present the first extended examination of fear development in hand-raised dogs and European grey wolves, using repeated novel object tests from six to 26 weeks of age. Contrary to expectations, we found no evidence in support of an increase in fearfulness in wolves with age or a delayed onset of fear response in dogs compared to wolves. Instead, we found that dogs strongly reduced their fear response in the period between six and 26 weeks of age, resulting in a significant species difference in fear expression towards novelty at 26 weeks. Critically, as wolves did not differ in their fear response towards novelty over time, the detected species difference was caused solely by a progressive reduced fear response in dogs. Our results thereby suggest that species differences in fear of novelty between wolves and dogs are not caused by a domestication driven shift in the first onset of fear response. Instead, we suggest that a loss of sensitivity towards novelty with age in dogs causes the difference in fear expression towards novelty in wolves and dogs.

animal behavior and cognition↗

bioRxiv2018

Revisiting the social brain hypothesis: contest duration depends on loser’s brain size

BackgroundBrain size is expected to evolve by a balance between cognitive benefits and energetic costs. Several influential hypotheses have suggested that large brains may be especially beneficial in social contexts. Group living and competition may pose unique cognitive challenges to individuals and favor the evolution of increased cognitive ability. Evidence comes from comparative studies on the link between social complexity and brain morphology, but the strength of empirical support has recently been challenged. In addition, the behavioral mechanisms that would link cognitive ability to sociality are rarely studied. Here we take an alternative approach and investigate experimentally how brain size can relate to the social competence of individuals within species, a problem that so far has remained unresolved. We use the unique guppy brain size selection line model system to evaluate whether large brains are advantageous by allowing individuals to better assess their performance in a social contest situation. Based on theoretical literature, we predict that contest duration should depend on the brain size of the loser, as it is the capitulation of the losing individual that ends the fight.\n\nResultsFirst, we show that studying the movement of competitors during contests allows for precise estimation of the dominance timeline in guppies, even when overt aggression is typically one-sided and delayed. Second, we staged contests between pairs of male that had been artificially selected for large and small relative brain size, with demonstrated differences in cognitive ability. We show that dominance was established much earlier in contests with large-brained losers, whereas the brain size of the winner had no effect. Following our prediction, large-brained individuals gave up more quickly when they were going to lose.\n\nConclusionsThese results suggest that large-brained individuals assess their performance in contests better and that social competence indeed can depend on brain size. Conflict resolution may therefore be an important behavioral mechanism behind macro-evolutionary patterns between sociality and brain size. Since conflict is ubiquitous among group-living animals, the possible effects of the social environment on the evolution of cognition may be more broadly applicable than previously thought.

animal behavior and cognition↗

bioRxiv2017

phylopath: Easy phylogenetic path analysis in R.

O_LIConfirmatory path analysis allows researchers to evaluate and compare causal models using observational data. This tool has great value for comparative biologists since they are often unable to gather experimental data on macro-evolutionary hypotheses, but is cumbersome and error-prone to perform.\nC_LIO_LII introduce phylopath, an R package that implements phylogenetic path analysis (PPA) as described by Von Hardenberg & Gonzalez-Voyer (2013). In addition to the published method, I provide support for the inclusion of binary variables.\nC_LIO_LII illustrate PPA and phylopath by recreating part of a study on the relationship between brain size and vulnerability to extinction.\nC_LIO_LIThe package aims to make the analysis straight-forward, providing convenience functions and several plotting methods, which I hope will encourage the spread of the method.\nC_LIO_LIphylopath is released under the GPL-3 license, and is freely available on CRAN (https://cran.r-project.org/web/packages/phylopath/index.html) and GitHub (https://github.com/Ax3man/phylopath).\nC_LI

evolutionary biology↗