Mother mongooses can adapt their body chemistry to shield their unborn pups from potential cell damage, but it comes at a cost. After giving birth, the mother might have higher levels of toxins in her blood. The findings were published in Frontiers in Ecology and Evolution last month.
Across the animal kingdom, investing in reproduction can often be costly to survival. According to one theory, pregnancy may increase the mother's level of toxic metabolism byproducts (or metabolites) that cause what’s called oxidative damage. Oxidative damage naturally occurs throughout the lifespan of both males and females, and high levels of it lowers the survival of both sexes. However, because it could have negative impacts on developing offspring, it would be good for females to lower those toxin levels somehow – even temporarily.
To study this so-called oxidative shielding in the wild, University of Exeter’s Emma Vitikainen and colleagues followed a population of banded mongooses (Mungos mungo) living in and around the Mweya peninsula at Queen Elizabeth National Park in Uganda over the course of five years. These well-studied females have a shorter average lifespan than males – 38 months compared to 42 – and the longest-lived female and male mongooses died at 11 and 12 years old, respectively. Females also begin reproducing earlier than males, at about one year of age.
By measuring amounts of malondialdehyde (MDA) in hundreds of blood samples, the team was able to calculate the animals’ levels of oxidative damage. They found that pregnant mongooses showed lower than expected toxin levels – which goes against theories that damage increases during pregnancy. They evolved a protective mechanism that specifically minimizes such damage.
"We think mother mongooses shield their offspring by reducing their own levels of oxidative damage during breeding," Vitikainen said in a statement. "However, she could be trading her own long term well being for the short term benefit of protecting the growing pups." Since the effect is only temporary, and oxidative damage returns to normal levels after the pregnancy, the researchers think protective mechanisms during pregnancy are unsustainable and may have potentially harmful consequences for the mother's survival.
Mongooses with the lowest levels of oxidative damage were also the most successful at reproducing. They stayed healthy and had the largest litters, and their pups had a better chance of surviving into adulthood. This shielding effect is likely caused by changes in the content of the mothers' blood, but the details are still unclear. "Mothers might be adjusting their physiology," Vitikainen added. "It would be quite a remarkable adaptation."