Link E. Olson

Specimen‐based data have played a central role in documenting body‐size shifts as a possible response to global warming over the last century. Identification of the drivers and patterns of these trends requires comparisons across taxa, often through meta‐analyses; however, a lack of repeatability within and interoperability (i.e. the potential for a dataset to be augmented for future research) among published studies is a major obstacle. We reviewed published studies on mammal body‐size changes in the Anthropocene, focusing on those that used museum specimens to analyse body‐size trends over time in at least one species. We assessed these papers for repeatability and interoperability with the following criteria: raw data and specimen identifiers were published and accessible, measurements were unambiguously defined, and potential sex‐ and age‐based size differences among individuals were accounted for. Most published body‐size studies have low potential for replication or augmentation; only one of 27 met all of our criteria. Although these 27 papers collectively generated an estimated 51,790 new body‐size measurements, only 1.25% (649) could be repeated or readily used in further investigations, as the remainder did not include raw data and/or specimen identifiers. Based on these findings, we recommend the following best practices in the study of body‐size trends. First, authors should explicitly define and justify all measures of size and quantify measurement error and publish all data, including measurements and specimen catalogue numbers. In addition to complying with the fundamental scientific tenet of repeatability, this minimizes redundant handling and the concomitant risk of damage to irreplaceable and often fragile museum specimens. Second, authors should test and account for the effects of demography, as some dimensions can change throughout an individual's life. Adopting these practices will improve the quality of body‐size studies, enhance the utility of extended specimen data from natural history collections, and enable researchers to conduct more expansive investigations of size trends over time.