Data used in Boulton et al paper on Xiphophorus birchmanni Note lines correspond to observations not individuals, with multiple observations of difefrent types (measures, behaviour, longevity) per individual. Fields are: Fish - individual identifier Sire -individual identifier Dam -individual identifier Brood_tank -tank of initial raising, a and b denote partitions of a single tank (unit - identified by number) within stack (upper case) Stack - set of 8 units on single water supply Unit - physical tank within stack Sex -1 female, 2 male, not necessarily know at measure (immature fish not sexable) ELD -early life density (Low vs High) LLD -early life density (Low vs High) SL -standard length (mm) WT -live mass(g) Status - juvenile vs adult (based on external morphology) Measure -1 to 13, monthly measures as described in MS Part -Part 1 was at initial density treatment, part 2 is post switch Measure_age -age in days of fish at measure gmCOMP -see text for definition, geometric mean group size experienced by fish to this measure Sex_ratio -see text for definition, mean sex ratio (defined by mature male presence) to this measure Trial -trial repeat number for behaviour Dayorder -order assayed within a day for behaviour Act -activity, proxy for boldness, see text for definition DOMscore -dominance score (see text for definition) DOMmeas -type of dominance measure; in main experiment (EXP) versus at end (END) Longevity -age of death (censused to last observation) gmCOMPlife -geometric mean number of compeitors over lifetime Sex_ratio_life -lifetime version of Sex_ratio surv - survival to end of part 2 (0/1)