Over 4 years after the start of data collection, our study showing qualitative individual variation in abnormal behavior in chimpanzees has finally been published in the journal Animal Welfare. You can find the article here
This article started as my Major Research project of my Master's degree back in 2017. It was the first time I was observing chimpanzees, and this research question was one that I largely thought of myself. It changed forms many times since then and has been rejected and repeatedly revised before arriving at its current state.
Abnormal behavior (such as eating one's own feces) by captive animals is often seen as a sign of poor welfare. However, by definition, abnormal behavior is neither negative or positive, it is simply behavior that is observed in captive animals that is less common or absent in wild populations. Finding out whether abnormal behavior is an indicator of poor welfare or not is essential if we want to improve the lives of each captive chimpanzees (and not only the one's that are most 'average').
Chimpanzees show strong differences in their behavior and personality, and we also found that their abnormal behavior repertoires varied considerably. Most chimpanzees appear to have a 'favorite' abnormal behavior that they show much more frequently than other behaviors. We also found tentative evidence that whether an abnormal behavior co-occurs with a known behavioral indicator of stress (self-scratching) also varies between individuals.
The main thing to learn from our exploratory analyses is that chimpanzees are each abnormal in their own way. If we want to accurately assess their welfare we need to focus on the individuals.
