Growth patterns, sexual dimorphism, and seasonal body mass variation in Plains Zebra of the Serengeti region, Tanzania

Saeideh Esmaeili; Peter J. Gogan; Kathryn A. Schoenecker; Ronald O. Skoog

doi:10.1093/jmammal/gyag044

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Growth patterns, sexual dimorphism, and seasonal body mass variation in Plains Zebra of the Serengeti region, Tanzania

Saeideh Esmaeili·Peter J. Gogan·Kathryn A. Schoenecker·Ronald O. Skoog

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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 collected 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 307 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 34 females and 115 males with recorded girth but missing body mass records. We applied 5 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 to 5 yr 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.

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Journal of Mammalogy Article

Source-reported bounding extent: -3.3117235724542695° to -1.8364185578710703° latitude; 33.5605083971619° to 35.26029133049684° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Saeideh Esmaeili, Peter J. Gogan, Kathryn A. Schoenecker, Ronald O. Skoog. 2026-05-28. Growth patterns, sexual dimorphism, and seasonal body mass variation in Plains Zebra of the Serengeti region, Tanzania. https://doi.org/10.1093/jmammal%2Fgyag044

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