TITLE OF DATASET: The effects of changing climate on skull size in the common shrew The data files contain the data presented in the article "Fifty years of data show the effects of climate on overall skull size and the extent of seasonal reversible skull size changes (Dehnel’s phenomenon) in the common shrew". Corresponding author: Jan R. E. Taylor, Faculty of Biology, University of Białystok, 15-245 Białystok, Poland, e-mail: taylor@uwb.edu.pl; Author: Dina K. N. Dechmann, Department of Migration, Max Planck Institute of Animal Behavior, 78315 Radolfzell, Germany. DESCRIPTION OF THE DATA AND FILE STRUCTURE: Two files include the data on 1) the size of the skulls of the common shrew, Sorex araneus, collected in the Białowieża Forest, E. Poland, between 1953 and 2004 (file name: "Skull dimensions.xlsx"), and 2) the meteorological data from Białowieża, from 1952 to 2004 (file name: "Climate Bialowieza.xlsx"). The size of the skull is often used as a proxy for overall body size, the trait which is pivotal for individual life histories. Three measures of skull size are included in the former file: skull (braincase) height, skull width, and skull length. Meteorological data (in the latter file) show climate warming in the Białowieża Forest; the calculated soil moisture deficit indicates drought increase. SHARING/ACCESS INFORMATION: Three meteorological parameters (temperature, rainfall, and the number of days with snow cover) are from the meteorological station in Białowieża. METHODOLOGICAL INFORMATION: Skull measurements Sorex araneus were collected between 1953 and 2004 in Białowieża National Park, preserved in alcohol and stored in the zoological collection of the Mammal Research Institute, Polish Academy of Sciences, in Białowieża. The skull height, length, and width (mm) of 502 S. araneus were measured using X-ray images of the alcohol-preserved specimens, as described by Lázaro et al. (2017). Climate parameters in Białowieża between 1952 and 2004 Mean temperatures (degrees Celsius), rainfall (mm), and the number of days with snow cover are the routine measurements from the meteorological station in Białowieża (52.7070 N, 23.8479 E). We computed the soil moisture deficit from monthly temperatures and precipitation using the Watbug program (Willmott 1977). DATA-SPECIFIC INFORMATION: Data-specific information for "Skull dimensions.xlsx" - measurements of 502 skulls of the common shrew, Sorex araneus: 9 columns: ID (=identity number of an animal); month (=month of catching); year (year of catching); age (1=juvenile, 2=subadult, 3=adult); year_cal (1=first calendar year of life, 2=second calendar year of life); sex (m=male, f=female); height (skull height, mm); width (skull width, mm); length (skull length, mm). Data-specific information for "Climate Bialowieza.xlsx" - meteorological data from Białowieża: 6 columns: Year, Month, Temperature (=mean daily temperature, degrees Celsius); Precipitation (=sum of precipitation, mm); Snow (=number of days with snow cover); Deficit (=soil moisture deficit, mm). LITERATURE CITED: Lazáro, J., Dechmann, D.K.N., LaPoint, S., Wikelski, M., & Hertel, M. (2017). Profound reversible seasonal changes of individual skull size in a mammal. Current Biology, 27, R1089-R1107. Willmott, C.J. (1977). WATBUG: a FORTRAN IV algorithm for calculating the climatic water budget. CW Thornthwaite Associates Laboratory of Climatology, Publications in Climatology, 30, 1-55.