Ecologists rate molluscs easy to study, yet only 6% in a UNSW survey worked with them

Birds and mammals dominate animal behaviour research, but the scientists who study them do not find them any easier to work with, according to a survey of 868 researchers by Pietro Pollo and Michael Kasumovic at UNSW Sydney. Molluscs were mostly judged simple to handle both outdoors and in the lab, yet only 5.88% of the respondents had ever collected behavioural data on one.

The survey, published in Ecology and Evolution on October 12 alongside a companion analysis of 1,383,803 papers, tries to explain a bias that ecologists have complained about for decades. UNSW publicised both studies on October 18.

Convenience explains choices inside a group, not across groups

The researchers sorted possible reasons into three buckets: rational ones such as logistics and social relevance, contextual ones such as what peers and supervisors work on, and emotional ones such as plain fondness for an animal.

Practical ease did matter, but only at a fine scale. Within a group such as birds, the genera that researchers found easier to locate, rear or buy were the ones more of them worked with. Across major groups the logic broke down: birds and especially mammals were judged equally or more difficult to handle than other animals, and they were still the most common choice.

Birds and mammals were each named by 42.58% of respondents, ahead of insects at 35.21% and fish at 24.05%. Popular species were also heavily shared. The fruit fly, the brown rat and the great tit were named by 22, 21 and 17 researchers respectively, and the most popular groups, mammals above all, had the fewest distinct species per response.

Supervisors and feelings fill the gap

Context weighed in strongly. The species a researcher worked on was often suggested by a supervisor, except for people who already held a permanent position. Researchers who thought of their species as a model organism also tended to see its behavioural literature as extensive.

Emotion lined up best with the big picture. Respondents felt more warmly about the groups they had worked with, most said their interest in a group grew after studying it, and the authors write that these affinities "closely mirrored" the taxonomic patterns in the literature. Bird researchers were also more likely to be birdwatchers than invertebrate researchers were to have an equivalent hobby.

The literature has barely moved in 25 years

The companion study shows how large the gap is. Vertebrates appear in 53.9% of ecology and evolution papers that mention animals, while making up 4.7% of described animal species. Across the field, the share of vertebrate studies has stayed roughly flat since the early 2000s, and within the same journals vertebrate papers drew more citations and media mentions than invertebrate ones.

Some neglected groups only get attention through vertebrates. Ticks make up 0.08% of arachnid species but appear in 20.1% of the papers that mention arachnids alongside other animals.

The authors suggest outreach featuring overlooked animals, more balanced teaching, and research placements with a wider range of organisms. "We don't know what we don't know," Pollo said in the UNSW release, arguing that the payoff of basic research on any one animal cannot be predicted in advance.

The survey only covered ethologists and behavioural ecologists, so whether the same mix of reasons drives choices in other fields of biology was not tested.