As with plants, animals over-produce offspring to compensate for the heavy losses that befall offspring at the hands of predators, a harsh environment, parasites, disease, and genetic defects. Over-producing offspring means an high upfront energetic investment. If only 6 out of 3,000 eggs survive to adulthood, there’s a lot of wasted energy in producing those extra 2,994 eggs (link). Time and energy invested in the 2,994 duds is time and energy siphoned away from supporting the 6. Fortunately females have a few options to help minimize the costs of reproduction, including (but not limited to):
- Paussing the pregnancy
- Reabsorbing the fetus
- Inducing an abortion
- Eating the offspring
- Letting the offspring fight it out
I’ve included other options in addition to abortion to highlight that abortion is but one strategy for females to avoid enduring undue burden to birth and raise offspring when the conditions are unfavorable.