Science Popular Science Female mice often have multiple sexual partners—for survival

This post was originally published on here

If a female house mouse mates with multiple male house mice, her litter could have multiple fathers. Polyandry, as this mating practice is called, is common for various species. Yet scientists are still investigating its purpose and the potential benefits of birthing half siblings within the same litter.

“Such multiply-sired litters have been suggested to produce benefits in low-quality environments that may be masked in higher-quality environments,” the researchers write in a study recently published in BMC Ecology and Evolution. “So far, however, the effect of environmental quality has only been tested in birds with equivocal evidence.”

Within this context, two researchers from the Max Planck Institute for Evolutionary Biology in Germany investigated polyandry in western house mice (Mus musculus domesticus). The team put hundreds of mice in each of a number of enclosures mimicking wild habitats. For four years, they gave the mice in some of the enclosures a high-quality diet. The others received a typical, less nutritious diet.They then tracked the mice’s mating behaviors and the results to shed light on reproduction methods in the face of this resource variable.

Ultimately, around one-third of litters in both the high-quality and lower-quality food habitats had more than one father. However, larger litters (the benefit of polyandry quantified by the study) only came from the lower-quality food habitats, with mothers birthing large litters in high-quality food habitats no matter the number of fathers. This indicates that the benefit of polyandry likely depends on the environment, particularly the food quality for the mother.

Related Mouse Stories

Scientists watch how mice learn, one synapse at a time

The dye in Doritos can make mice transparent

Mice may be able to recognize their own reflections

Earth welcomes baby mice from space

“Our results suggested that polyandry provides greater lifetime fitness benefits when resources are of poorer quality,” the team explains in the study. “In other words, polyandry potentially yields its greatest advantages when resources are a limiting factor, but contributes little when conditions are already favourable.”

The results also highlight that a specific reproductive behavior can result from particular situations. In times of lower quality resources, females might engage in polyandry in a way that raises the probability of some babies’ survival. This strategy is called bet-hedging, and it might not be as needed when there is lots of food. However, females still usually engage in it, pointing toward another inquiry—why?

The study paves the way for future research into how and why shifts in ecological pressures impact animal mating behaviors, potentially furthering our understanding of certain differences among species in changing habitats.