Strong social networking plays an important role in human relationships. New research on female red deer shows that those bonds are also crucial for their reproductive success and survival.
The study, which looked at more than 40 years of data for free-ranging adult female red deer on the Isle of Rum in Scotland, was recently published in Royal Society Open Science.
"I'm interested in social networks," says Dr. Kathreen Ruckstuhl, PhD, the study's lead author and a professor with the Department of Biological Sciences in the Faculty of Science. "We know a lot about humans and how important it is, but we really don't know a lot about ungulates, or hoofed animals."
Her study, which included researchers from Max-Planck-Institute for Evolutionary Anthropology in Germany and the University of Cambridge in England, looked at 295 deer belonging to 24 different female (matrilineal) groups.
Ruckstuhl says these deer have been monitored since 1974 with weekly censuses.
Kathreen Ruckstuhl during the bighorn sheep rut in December 2025. Photo Courtesy Kathreen Ruckstuhl
"The interesting thing for me was to look at a society such as the red deer where we know they are sexually segregated males do their own thing during the year, and females are in their groups," she says.
Research reveals subgroups within red deer herds
Ruckstuhl's research found there are subgroups that mainly consist of mothers and daughters that take care of each other.
"We found strong correlations between the strength of these social bonds, female survival, the number of calves she gives birth to and also the number of calves that make it into adulthood where they can have their own calves," she says.
A previous study showed that losing a mother can also have an impact on the offspring, meaning there's a higher risk of them dying if the mom dies even when her daughters are adults.
"I was interested in knowing the potential fitness benefits of them grouping with relatives and there seems to be quite a considerable benefit," Ruckstuhl says.
"It looks from the outside that they are randomly associating yet they have these strong relationships that they maintain throughout their lives. They are tightly knit matrilines."
Red deer display strong social structure
Similar social bonds have been shown in primates, but she says it wasn't known about red deer. The animals live in a fission-fusion society, a social structure where group sizes change frequently with members splitting into smaller groups to forage or travel, and merge to sleep, socialize or defend territory.
In these red deer, grouping is not just about predator avoidance, she adds, noting they appear to co-operate with the other members of the group to "babysit" the calves and defend one other against other groups of females.
Ruckstuhl says the research can be applied to other ungulates such as elk, mule deer or white-tail deer in Canada when it comes to conservation and herd management.
"If you think about translocations, if you think about wanting to repopulate an area with an ungulate, for example, and you are randomly picking young individuals, you don't have that social network," she explains. "You are basically breaking it up.
"Knowing that (social bonds) are so beneficial for these individuals, you should take advantage of that when you do translocations, translocate individuals that are always together."
Importance of social networks underestimated
Wildlife such as elk and deer, she notes, already face many other problems when released in a new environment, because they must learn everything about it. So, keeping the social networks could help overall survival.
"Fundamentally, we are underestimating the importance of social structures and strong social bonds," concludes Ruckstuhl. "We are ignoring how important it is potentially for many of these species.
"Preserving group structure supports long-term population stability."
