Final answer:
Female red deer may produce offspring with different sex ratios due to natural selection favoring traits that prevent pregnancies in females with low fat reserves, potentially affecting birth sex ratios.
Step-by-step explanation:
The concept under scrutiny relates to how female red deer (Cervus elaphus) may adjust the sex ratios of their offspring. This adjustment could potentially be explained by several mechanisms, including frequency-dependent selection, selective abortion based on the female's condition, local mate competition, or even temperature-dependent sex determination. However, evidence suggests that natural selection favors traits that prevent pregnancies in female elk with low fat reserves, thereby affecting the sex ratio at birth.
Natural selection can lead to the development of traits that ensure only female elk with sufficient energy reserves become pregnant and carry the pregnancy to term. This has become a predominant trait in current elk herds, which can contribute to changes in sex ratios as healthier females may have a different sex ratio compared to those with lower fat reserves.
Female elks with poor condition may not only have fewer opportunities to reproduce but may also produce offspring with less chance of surviving, thus influencing the sex ratio. The survival of the offspring is closely related to the mother's health and resources that can be transferred to the fawns. Key factors such as host conditions and ability to resist parasites like the deer ked affect the resources available for successful fawn development and survival.