impMAT gives phenotypic data associated with 243 striped mouse parturitions in csv format. Each row represents a separate parturition. Some females bred more than once, and some bred in more than one year. Please refer to Methods for further information on how these data were collected and imputed. impMAT files were generated using multiple imputation based on stripedmouse_rawdata in R using the package Amelia 1.7.1. This generated 10 data sets where missing values are filled in with values that reflect the observed values of the different variables in the dataset and the levels of uncertainty for missing values. The 19 columns are defined as follows: (untitled) - unique identifer created by the R package Amelia during multiple imputation age - age in days of the female at parturition. Missing values are filled in using multiple imputation. Observed values are integers. ref - unique identifier for the reproductive attempt year - year of parturition, a 6-level factor id - unique female ear-tag number (note that some females bred more than once) group - the group that a female belonged to natalknown - a binary flag to indicate the level of certainty in determining a female's natal group: known (yes) or assumed (no). Natal group was inferred from behavioural observations for individuals that were trapped as adults and for which genetic information was unavailable. tactic - reproductive phenotype, a 4-level factor parturition_date - the ordinal date (where 1 Jan of any year is 1) when a female gave birth massp - mass in g of the female on the approximate day she conceived. Missing values are filled in using multiple imputation. Observed values are given to 1 or 0 decimal places. fgroup - the number of female adult relatives alive on the night before a female's parturition nobreeds - the number of breeding attempts a female made in a given breeding season mintemp - the minimum ambient temperature at parturition (°C) leavebirth - the number of days between leaving the group and giving birth; this is set to NA for communal breeders (which do not leave the group by definition) and females without living relatives (not relevant for testing hypotheses in this paper). conceived - whether the female was group-living (group) or solitary-living (alone) when she conceived, a 2-level factor nightsalone - the number of days between leaving the group and returning; this is set to NA for non-returners changesnest - whether females moved to a new nest (yes) or remained at their original nest (no) when they became temporarily (i.e. returner) or permanently solitary; this is set to NA for communal breeders (which do not leave the group) and solitary breeders without relatives (not relevant) fgroupbeforesol - the number of adult females with which a female was sharing a nest on the last night she was radio-tracked before she became solitary distance - distance moved between the original group nest and the new nest by solitary breeders and returners; this is set to NA for communal breeders and solitary breeders without relatives, and also for other females where this was not measured in the field