As researchers working to understand animal behavior, we have studied only a small subset of the more than 1.5 million described animal species. This is unavoidable, as there are many more species than scientists. But the animals we work with are our windows into nature, and it is increasingly clear that our field revolves around animal subjects that simply do not reflect the diversity of the natural world.
Studies in related fields such as ecology and conservation have repeatedly found that research effort is skewed towards warm-blooded vertebrates (birds and mammals) and against cold-blooded vertebrates and invertebrates in general. Our well-documented preferences for what we consider to be attractive or charismatic creatures may be limiting our contributions to a broad understanding of nature.
Does it matter that there are five times as many publications per year on primates as there are on beetles?
To test whether these skews exist in animal behavior research, we assigned taxonomic information to the 4,076 research articles published in the journal Animal Behaviour from 2000 to 2015 and compiled a data set that combined this with citation metrics for each article. By comparing this data set to actual species numbers, we were able to quantify the direction and magnitude of taxonomic skew in published papers.
Our findings can be summarized in two major points:
First: The warm-blooded vertebrate skew was intense. Almost 85 percent of described species are arthropods, but more than 70 percent of publications were on vertebrates. Birds and mammals alone accounted for well over 50 percent of publications, despite representing less than 2 percent of all animal species.
Second: In a world where citations are used to measure impact, publishing on understudied systems comes at a cost to the researcher. Publications on vertebrates received more citations on average than arthropod papers. They were also far more likely to be “blockbuster” publications with more than 100 citations.
How do we resolve this problem? First, we have to agree that there is one.There is no law that says we must invest as much effort studying dung beetles as we do studying chimpanzees. Some would argue that biologists’ work is intended to generate knowledge that can benefit humanity, and that it makes sense to focus on taxa that are best suited to addressing human-relevant questions. So does it matter that there are five times as many publications per year on primates (fewer than 500 species total), as there are on beetles (with a staggering 240,000 described species), as our study shows? We think it does.
For theorists, a narrow taxonomic focus does a disservice to all branches of the animal sciences whose goals are to understand the broad processes and patterns of the natural world. When we limit ourselves to a narrow subset of life, we generate narrow answers to broad questions. For pragmatists, a narrow focus makes it challenging to apply insights from animal behavior research to real-world problems. For example, insects are a critical part of most terrestrial food webs. If we study only a handful, how do we predict how changes in climate will affect their dispersal, or their foraging behavior, or the welfare of the vertebrates that depend on them as food? We are not saying that the intensity of study should match biodiversity. We are saying that it is critical to try to learn more about a broader range of organisms.
Truly resolving this issue will require an understanding of its causes. For example, might human preferences for charismatic species affect what we consider to be important or broadly relevant science? Previous work shows that papers on non-model organisms have more broadly framed introductions, suggesting that the bar for relevance is higher when the taxon is less appealing.
Our demonstration of uneven citation patterns is also consistent with this. We must ask some uncomfortable questions: Do papers that differ only in their study subjects get treated differently by reviewers or editors? Do grants? Do job applications? We can speculate, but these questions can, and should, be answered empirically. Luckily, we are members of a community that is equipped to do exactly that.
In the meantime, we suggest three ways to engage with this issue:
Be aware of your own potential bias when reviewing grants or papers: Ask yourself honestly whether your assessment of the quality and relevance of the work is a result of the quality of the science or of the taxon under study.
Be proactive when citing other publications: Publications on birds and mammals are more likely to cite within their taxon than are publications on non-model systems. In addition to reading broadly, make systematic efforts to consider the relevance of studies asking similar questions in other taxa.
Keep the conversation going: How big a problem is all of this? How can we determine the causes underlying these patterns? Should established researchers consider branching out taxonomically? What can my department do; what can my journal do?
We have strong evidence that the taxonomic research skew exists, and that it is severe. We have some hypotheses about causes. We have the data needed to answer some of the most pressing questions. Now, all we need is the will to explore the issue further.
Malcolm F. Rosenthal is a postdoc in Damian Elias’s lab at the University of California, Berkeley, and formerly a researcher in the lab of Maydianne C.B. Andrade, an evolutionary ecologist at the University of Toronto, Scarborough.