This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
A fascinating new paper just came out in Nature Communications and I intend to blog it in the usual manner, but I thought I'd try something new first. Check it out:
The Research Question
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...According to life history theory, mothers should invest in their offspring if this enhances offspring survival and fitness, and if the fitness benefit to mothers from increased offspring fitness exceeds the cost of their investment. Whether the maternal environment influences the fitness and reproductive value of sons is unknown in most mammals because male mammals usually disperse and, thus, few studies have matched maternal quality to the fitness and reproductive value of sons after dispersal. In the red deer (Cervus elaphus), a species with pronounced sexual dimorphism, in which male fitness is linked to body size and fighting ability, a privileged upbringing by a mother of high social status provides sons with fitness benefits during adulthood. Whether a privileged upbringing also provides fitness benefits to sons in multifemale multimale mammal societies in which male fitness depends on how well males conform to female mate-choice preferences rather than a male's fighting ability or body size is currently unknown.
The Main Finding
The reproductive success and evolutionary fitness of male spotted hyenas is affected by the social status of his mother.
What do you think could explain this finding?
Some important variables to consider:
The spotted hyena (Crocuta crocuta) is a large carnivorous species with minimal sexual dimorphism. This means that the two sexes are more similar than they are different, particularly with respect to features like color, body size, and ornamental body parts like antlers, feathers, or horns.
The spotted hyenas live in "highly structured, female-dominated social groups called clans," in which access to resources is determined on the basis of social status. For that reason, females of high status have higher reproductive value and success than low-status females.
Hyena groups are organized on the basis of matrilines. "In these societies, females usually remain in the group in which they were born, form matrilines with related females, and create linear dominance hierarchies...daughters acquire a dominance position close to and below that of their mother."
Early maternal investment in her offspring is quite high. For example, the lactation period lasts for a period up to two years.
Female offspring generally remain in the clan into which they were born, and retain their social status (thanks to the status of their mothers) into adult life, as long as they retain the support of a close female relative.
By contrast, male offspring typically leave the clan into which they were born after some time, and immigrate into another clan. "They join the new clan at the bottom of the male social hierarchy, observe strict conventions of social queuing and increase in status with increasing tenure when higher-ranking males emigrate or die."
Male reproductive success is dependent on how well the males conform to the preferences of the females. Which is to say, females have complete control over who gets to mate with them.
Tomorrow, you will be able to find a post detailing the findings of this paper in my usual style, but I thought I'd try something different today. In the comments, share your thoughts, guesses, and hypotheses in terms of what the mechanisms might be that cause an increase in the reproductive success of male spotted hyenas on the basis of their mothers' social status.
And check back tomorrow to find the answers.
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