Choosing mates based on how attractive they are to you is not as shallow as it sounds.
Female mice seem to be able to choose the males they will make better babies with — babies with stronger immune systems to fight off disease, specifically.
That's what researchers at the University of Veterinary Medicine Vienna found in a new study published Jan 23 in the journal BMC Evolutionary Biology.
In the lab, the researchers let some female mice mate with a male they were interested in, while others were set up in "arranged" matings. The researchers then tested the babies immune systems.
"Our findings provide the first direct experimental evidence to our knowledge that partner preferences enhance offspring survival following infection," the authors say in the paper.
The scientists think the research could be helpful for understanding how our genes help us fight off infections.
Sexy mice
Scientists have long thought that given the choice, females will choose males that are healthy and disease-resistant and so will produce offspring that are also healthy and disease-resistant. They can tell the healthy males from the unhealthy males based on secondary sexual characteristics — things like larger body size and more muscle mass.
But this has all been a theory — studies attempting to confirm the theory have only measured disease resistance indirectly by looking at things like the amount of parasites the offspring have.
In the new study, the researchers found that females mated with their preferred mate were more likely to get pregnant and had more babies. The babies were then infected with the bacteria Salmonella to see how well their immune systems could fight off the disease.
Stronger babies
Of the 72 baby mice infected with Salmonella, 53 survived to the end of three weeks. You can see the difference in the survival of the babies that came from preferred mates and non-preferred mates in the graph below.
The babies from "love"-matings were more likely to survive:
The dose of Salmonella didn't make a significant difference in whether the baby mice survived, so the researchers don't think the preferred mating gave the the baby mice an enhanced resistance to Salmonella specifically. Instead they seemed to have a generally enhanced ability to fight off disease — a stronger immune system.
The scientists still need to figure out why the preferred-mate babies were healthier. Was it because the female mouse could tell that the preferred male was of better genetic stock, or because females that were mated against their preference devoted fewer resources to her pregnancy?