May 5, 2004

Older may be wiser when it comes to mothering

McMaster researchers find older mama gerbils produce healthier pups

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A mother Mongolian gerbil nurses her young pups. McMaster researcher Mertice Clark has found that older mothers spend more time with their offspring and raise healthier pups.

Hamilton, ON - Does older mean wiser? When it comes to motherhood for Mongolian gerbils, the answer is apparently yes.

In her studies of these small mammals, McMaster University researcher Mertice Clark has found that the older a mother is, the more time she spends with her offspring and, perhaps as a result of that increased attention, the healthier her pups are.

Clark, an adjunct professor in the department of psychology, explains, “Maternal effort increases with age. Older Mongolian gerbil mothers invest more in their offspring.”

To determine the effect of age on maternal effort, researchers divided 48 gerbils into four groups determined by age. Females were 35, 70, 90, and 120 days old. By observing the mothers with their babies, researchers found that the older a gerbil was, the more devoted she was to her offspring.

But how do you measure maternal devotion?

After a litter was born, the mother was removed from her cage to be weighed. At that time, researchers moved her pups from their nest to another area of the cage. When the mother was returned to the cage, researchers observed that older females were far more likely to return their pups to the nest than were younger females.

As well, older females spent more time than younger females with their babies. The older the gerbil mother was, the more likely she was to be in contact with her young or to nurse them.

Clark says that her research findings may be applied to motherhood among humans as well. “Our results raise questions in terms of younger mothers versus older mothers,” she explains. “Girls who have children very young may behave quite differently towards their offspring than women who wait to have children until they’re 40 or 45.”

For Mongolian gerbils, the extra attention provided by older mothers seemed to be beneficial to the babies. Pups reared by older mothers gained more weight than did pups reared by younger mothers.