Too threatened to try: how extinction risk drives research neglect in rays and skates

Global biodiversity loss demands that research effort be directed towards species most at risk. Yet conservation science is biased by species' accessibility and perceived charisma, raising concerns that threatened species may be overlooked. We apply a structured causal modelling framework to 651 species of rays (superorder Batoidea), a highly threatened yet understudied lineage of cartilaginous fishes, to disentangle the drivers of research effort. We quantify the causal effects of taxonomy, extinction risk, accessibility (range size, depth, economic context, year of description) and charisma (body size, shape, patterning and colouration) on species-level research outputs from more than 7000 publications. Research effort was strongly taxonomically biased, driven by accessibility and charisma, with shallow depth, broad geographic ranges, large body size and distinctive morphologies attracting disproportionate attention. Extinction risk exerted a counterintuitive nonlinear effect: Critically Endangered and Endangered species received significantly fewer publications than Near Threatened and Vulnerable species and were comparable to Data Deficient species. This effect is consistent with a ‘Goldilocks’ zone in which species are threatened enough to justify research but not so threatened that it becomes prohibitively challenging. Systematic research bias away from the species most in need undermines conservation efforts. Realigning research priorities is essential to combating the biodiversity crisis.