Seasonal biases in data collection cause conceptual gaps in animal ecology

Samuele Ramellini , William H. Bray, Yiqing Chen, Roger Fuste, Franziska Hacker, Xingyi Jiang, Kushini Kalupahana, James Klarevas-Irby, Edward Lawrence, Chun-Chieh Liao , Brendah Nyaguthii, Esha S. Shekar, Rhiana Woods, Damien R. Farine

1. Animal life cycles are structured into seasons with major differences in behaviour. Yet much of the data that inform policy and predictive modelling is drawn from studies conducted when animals breed. This temporal research bias overlooks key seasonal and life stages in the ecology of animal populations, such as high over-winter mortality periods. Yet, it is unclear whether this bias also extends to the conceptual focus of the research questions in the ecological literature.
2. Here, we test whether there is a bias in research focused on breeding vs. non-breeding research questions. We evaluate the animal ecology literature by reviewing >6,000 studies in the last decade, discriminating between when the data were collected from what the focus of the research was. We also evaluate the methods and approaches used in each study to explore how different methodologies have contributed (or not) to closing the gap between breeding and non-breeding studies.
3. Our analysis shows that while most studies in ecology collect data during the breeding season—a pattern that has not changed over the last decade—the majority of this research asked questions about non-breeding ecology. We also show that studies conducted during the breeding season are more likely to conduct experiments and have larger sample sizes. By contrast, studies conducted during the non-breeding periods of organisms’ lives relied more on indirect methodological approaches, such as biologging.
4. Our results show that the seasonal bias in ecology is one of data collection rather than research focus. While this suggests the bias in research may not be as severe as previously thought, our results reveal that our understanding of ecological processes outside of breeding are likely to have limited seasonal coverage, with persistent gaps in capturing how animals survive some of the harshest conditions that they experience.