Data from: Growth Patterns, Sexual dimorphism, and seasonal body mass variation in Plains Zebra of the Serengeti region, Tanzania
Data files
Jun 02, 2026 version files 38.88 KB
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README.md
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zebra_data_29May2026.csv
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Abstract
Knowledge of growth patterns and physical properties of animals helps researchers assess population characteristics and health in the field. Information on age-specific body measurements and growth patterns is rare in ungulates because examining a large portion of a population is time-, budget-, and personnel-intensive in the wild. We compared age- and sex-specific body measurements from 442 Plains zebra (Equus quagga boehmi) culled in the Serengeti region, Tanzania, between 1969 and 1971. The dataset contained 309 males and 133 females. We found that males were on average, 2.8% larger than females in body measurements of heart girth, height at shoulder, neck-body length, hind foot length, and the body mass, indicating minimal sexual dimorphism in adult plains zebra. We used polynomial regression to explore the relationship between heart girth and body mass and applied third-degree polynomial regression models to predict body mass for 37 females and 118 males with recorded girth but missing body mass records. We applied five non-linear models, Gompertz, von Bertalanffy, Bertalanffy–Pütter, logistic, and Richards, to characterize sex-specific growth trajectories for each trait. Our results showed that different traits followed different growth patterns, with size asymptotes reached by ~2–5 years depending on trait and sex. Seasonal trends in adult body mass were also evaluated using generalized linear models incorporating sex and cyclical effects of day of year. While female body mass showed little seasonal variation, adult males exhibited a 16.9% increase in mass during the wet season, followed by a sharp decline, suggesting greater seasonal plasticity and energetic investment. Our work is one of the few studies on body size and growth in wild equids, which provides new information on age- and sex-specific growth trajectories for comparison across zebra subspecies over time and space
Dataset DOI: 10.5061/dryad.4qrfj6qsk
Description of the data and file structure
We sought to determine sex-specific growth rates and body mass, allometric relationships and seasonal variation in body mass in E. q. boehmi. To do this we collected body mass and morphometric measurements from plains zebra culled in the Loliondo Game Controlled Area (LGCA), Tanzania, by a private company (Wildlife Services, Pty) in 1969 and morphometric measurements from plains zebra culled by the Tanzania Game Department in 1970 and 1971. These data provide a rare opportunity to quantify allometric growth patterns, the extent of sexual dimorphism in a wild population and seasonal variation in body mass.
Files and variables
File: zebra_data_29May2026.csv
Description:
Variables
- FIELDNUM: Alphanumeric collection number assigned in the field; n/a = not assigned
- OTHER_FN: Other sample number assigned later
- date: Date of collection give as day of month, abbreviation for month, and last two digits of year
- sex: Male or female as determined by inspection of carcass
- age: Age class determined by wear and replacement of upper incisors following Klingel (1965) and Klingel & Klingel (1966)
- age_group: Grouping of age classes
- weight_original_kg: Whole body mass in kilograms after conversion from pounds; n/r = not recorded
- adj_weight (for pregnants): Estimated whole body mass in kilograms of pregnant females after substracting weight of the conceptus; n/a = not applicable when whole body mass not recorded and for all males
- weight (original and adjusted): Mass in kilograms either taken in the field or adjusted for a conceptus in pregnant females; n/a = not applicable when whole body mass not recorded and for all males
- heart-girth_mm: chest circumference in millimeters measured immediately behind the foreleg; n/r = not recorded
- height_shoulder_mm: Distance in millimeters from the withers to the hoof tip of fore leg; n/r = not recordedhind_foot_mm: Distance in millimeters from the hock to the tip of the hoof
- neck_body_mm: Distance in millimeters from the anterior atlas joint to the sacro-coccygeal joint along the body contours to the base of the tail; n/r = not recorded
- predicted_weight: Predicted body mass in kilograms using univariate linear regression models based on morphometric traits; n/a = not available based upon absence of predictive data
- weight (original_adjusted_predicted): Original mass as recorded, or adjusted mass for pregnant females or predicted mass in kilograms used in our calculations; n/a = not available based upon absence of predictive data
- fetal_weight_g: Mass of fetus in grams; n/r = not recorded for pregnant females; n/a = not applicable for non-pregnant females and males