A researcher from Iowa State University has revealed that contrary to existing belief animals do not look after themselves when their life is under threat. The researcher found that sick female deer mice channeled their efforts in producing healthier offspring.
Lisa Schwanz, a researcher in the department of ecology, evolution and organismal biology, examined the size of offspring for both infected and healthy mice.
She found that females that had been infected with a parasite produced larger offspring than healthy females.
"Organisms are predicted to decrease investment in current reproduction when parasitism has the greatest impact on current reproductive ability," Schwanz said.
In other words, "infection in animals typically leads to responses that invest in the survival, not offspring," she added.
However, in deer mice, the opposite was happening.
For the study, Schwanz infected 30 female deer mice with a parasite that lowers the future reproductive ability and eventually kills the mice.
She said that by producing larger babies now, the mice are probably compensating for this loss in future reproduction.
She also kept 21 deer mice healthy as a control.
After several weeks, all the mice were paired with mates. When the baby mice were born to both infected and healthy mothers, the offspring were tagged and weighed.
Schwanz found that the offspring of the infected mothers were bigger.
In deer mice, larger offspring are more likely to survive and reproduce.
"This shows there is a lot of diversity in the ways animals deal with infection," she said.
"It is really striking to find such strong results," she added.
The type of parasite used in the study was an indirect parasite, meaning that it cannot be passed from one mouse to another.
A deer mouse can only get infected from a source other than deer mice.
That way Schwanz was able to ensure that mothers did not infect their offspring.
The study is published in New Scientist magazine.