<p>Chemical defense mechanisms in certain plant seeds yield secondary metabolites that can adversely affect rodents. In forest ecosystems, acorns high in ellagitannins (ET) serve as a significant nutrient source for rodents; however, the long-term impacts of ingesting tannin-rich acorns on reproductive organs and overall reproduction remain unclear. In this study, four types of artificial seeds with different ET contents (0, 2, 7, and 12%) were fabricated to simulate various acorn types. We investigated the effects of ET on the survival and reproduction of Kunming mice (<i>Mus musculus</i>). Results revealed that increasing ET content significantly inhibited weight gain and reduced survival rates, with male mice being particularly sensitive. High ET levels were associated with alterations in the physiological structure of the ovaries and testes, premature aging, and other deleterious effects, which may impair sperm quality in males and compromise fertility in females. Furthermore, a medium ET content inhibited an increase in embryonic body length, disrupted the structural and functional integrity of embryos, and reduced the number of blood cells in the labyrinth layer of the placenta. These findings suggest that tannins in <i>Quercus</i> seeds may affect rodents' growth and reproduction, thereby potentially playing a regulatory role in rodent population dynamics.</p>