Captive multi-mammate mice, Mastomys natalensis, were paired and kept on one of three treatment diets (low, medium and high protein) in order to assess differential maternal investment in the sexes, and sex-specific resource allocation of offspring. The influence of maternal dietary protein content on maternal reproductive performance, sex-specific body composition of pups and pup growth from birth to weaning was determined. Mothers on the high protein diet were larger than those on the lower protein diets, and produced more male than female offspring. Mothers on the lower protein diets did not produce sex-biased litters. Maternal dietary protein intake did not significantly influence litter size or the interval between litters. Litters produced by mothers on the medium (15%) protein diet were significantly larger than those produced by mothers on the low (10%) protein diet. There were no sex-specific differences in body size or body tissue composition of pups at birth of at weaning within each treatment group. At weaning, pups in the 20% protein treatment group had proportionately greater amounts of lean tissue and less body lipid reserves than pups in the 10% protein treatment group. Pups in the 20% protein treatment group were also larger, and had faster growth rates, than those in the 10% protein treatment group. Weaned pups in the 15% protein treatment group had the fastest growth rates and greatest energetic contents of all of the treatment groups. These results suggest that larger mothers on the high (20%) protein diet show differential investment in the sexes, not by allocating more resources to individuals of that sex, but by producing more male than female offspring. Maternal dietary protein intake did not appear to influence the reproductive output of mothers, but did affect pup mass, growth rates and body composition which would have implications for their future success and survival.
Dissertation (MSc (Zoology))--University of Pretoria, 2006.