Male pregnancy occurs only in seahorses and their relatives, and happens when females deposit their eggs in a pouch located on the male. The pouch serves a similar function as the human uterus and provides nutrition and protection for the offspring while they develop. In a recent study published in Nature, researchers looked at how male pipefishes manage these pregnancies and find surprising behavior.
First, the researchers confirmed that the male pipefish prefers to mate with larger females. This maximizes evolutionary fitness (survival of the fittest) because larger females lay more eggs and their eggs have a greater chance of surviving. Interestingly, the shorter the male, the stronger the preference for a large female. I’m going to let you draw your own conclusions as to the origins of Little Man Syndrome.
Second, the researchers found that the chances of survival of the offspring depend on previous pregnancies. If a male really invested himself in a previous pregnancy and spent a lot of energy caring for the offspring of a larger female, the chances of survival of a later pregnancy from a smaller female are much lower. This essentially means that the male can gauge the “attractiveness” of a female and distribute his resources accordingly. In some cases, when forced to reproduce with a small female, males can partly or even completely abort the offspring (by not spending energy for their nutrition and care) to conserve their reproductive potential for when they hit the jack pot chunky female. Kind of a blow to the supermodels of the pipefish world, if you ask me.
Overall, the study suggests that male pipefishes have much greater control over reproduction that we initially thought, and certainly much greater control over reproduction when compared to the standard female mammal pregnancy scheme.
Now let’s see if we can find some relevance to this study and make it a two-for-one. Can you find any relevance for us in this study, in aspects of the study, or even in questions it raises? Contribute your thoughts in the comments!
Reference: Post-copulatory sexual selection and sexual conflict in the evolution of male pregnancy. (2010) Paczolt KA, Jones AG. Nature 464(18):401-4.