The amount and composition of milk used in hand-raising ursids significantly influences development, growth rates, abnormalities, and survival rates of cubs. This study analyzes hand-raised cub feeding (mL/kg) and mass (kg) data for Bornean sun bear (Helarctos malayanus euryspilus) cubs collected at the Bornean Sun Bear Conservation Centre in Sabah, Malaysia, since 2013 to provide comparisons for practical application. Using a linear model to assess growth rates through mass and using a generalized linear mixed model with random effects (GLMMer) to model the mass increases of 10 hand-reared cubs from daily or semiweekly measurements, we determined whether differences between males and females were due to sexual dimorphism. We found that average male mass (ȳ2 = 16.1 kg) was 26.7% more than average female mass (ȳ3 = 11.8 kg) with similar results for each quantiled age group. Significant response variables identified were sex, age, milk volume fed, individual bear health status, and the Random Milk Variable, although other masking variables may exist. The milk formula amounts (g/mL) fed to each bear varied by mass (kg) as well as individual, random bear health status, and milk variation due to clinical judgement captured through the Random Milk Variable. This model allowed us to support the hypothesis of sexual dimorphism in sun bears at an early age. Additional research should assess sun bear milk composition to more closely simulate natural milk for cubs in rehabilitation.
- Volume 37
- Issue 9
- Pages 1-14
- Publication Date 6 July 2026
- DOI 10.2192/URSUS-D-24-00020
- File Size 1.21 MB
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