How understanding the social networks of other species can help
Coronavirus, or COVID-19, is front and center these days. Some people are unconcerned, others are worried, and a few are panicked. Amid quarantines, school closures, recommendations to prepare for possible isolation or working from home, one phrase linked to all of this that we keep hearing is “social distancing.” Some people might think this just means standing farther away from others, but really it means reducing the physical interaction with your social contacts. Perhaps then we should call it "physical distancing" Why does this matter? Why are contacts being tracked down? And, most importantly, how can we implement this properly?
Let’s use animal social behavior and disease transmission research to get some perspective. Animal behavior studies have borrowed extensively from social scientists and have been studying the social networks of other species in great detail. Think Facebook, Twitter, Instagram, etc. for animals. When it comes to social networks, there are a few things we measure (okay there are lots of things, but we’ll only cover a few). The number of social contacts one has is called “degree”. The higher the degree, the more social connections you have. In one of my studies of prairie dog social networks, the number of different social contacts an individual prairie dog had ranged from 1-8. The one with 8 degrees might be said to have more friends, a bigger network, more connections. When it comes to social media followers, that’s great. When it comes to disease transmission, not so great.
Another measure we use is something called “betweenness”, or closeness, which give us a sense of how much influence a particular individual has withinand acrossnetworks. Meaning, in the case of prairie dogs, some individuals are connected to others through an intermediary. For a given prairie dog, human, dolphin, or Tasmanian devil, the higher the number, the higher the influence. For reference, many people have heard the popular phrase “6 degrees of separation from Kevin Bacon”, which simply refers to the “friend of a friend, of a friend situation”. Thus, you don’t connect with Kevin Bacon directly (shame), but on average, you theoretically could through six “friends of friends” contacts.
Now let’s turn to animals and disease to understand why we care about contacts, connections, and tracking them down during what is arguably already functionally a pandemic. I’ll use the ever charismatic Tasmanian devil because they are not particularly social creatures, they don’t live in groups, and are somewhat cantankerous, yet provide a terrific example of how disease can travel through networks. When outbreaks of Devil Facial Tumor Disease, a very aggressive transmissible cancer, began spreading and threatening the species with extinction, scientists ramped up research efforts to understand how it was affecting so many devils. What they discovered was that the contact network had an enormous impact on the spread of the disease. But they aren’t traditionally “social” so how could this be? First, they aren’t completely asocial, females do interact, but the big whammy came during the mating season where in essence, ALL devils in a population were physically connected through some big influencers. Essentially, the population became one giant network.
What does this mean for us right now and why are experts making recommendation that would effectively shrink your network? The smaller your network, the fewer contacts, the lower the disease transmission rate to the entire population. Not really an option for Tasmanian devils, but certainly within our power to control temporarily by simply reducing the number of physical contacts we make. We have many ways to connect, verbally and visually, without being in each other’s physical presence – start using them!
Finally, we have all heard of “cliques”, usually when thinking about our unfortunate time in high school. This is another measure of social networks and, just like in high school cliques refer to sub-groups within a larger group. We have cliques, cows have cliques, deer have cliques, prairie dogs have cliques- you get the picture. The more that cliques are separate from one another, the more smaller networks are embedded into larger networks. Cliques can put the brakes on disease transmission, but where there is a connecting individual between two cliques it can still spread with frightening speed. This is why health officials are working so hard to contact trace. For example, if someone goes on vacation and catches COVID-19 and then a) goes to work and b) goes to church, the work network and church network may normally be separate but for the fact that there is one individual common to both. This individual may be a super spreader and the result is like the center of a bicycle wheel, all cases can be traced to them. Once again, the smaller and less well-connected your network or cliques within networks are, the slower the transmission rate.
This can be crucial for stemming the spread of disease. For example, deer mice are susceptible to a virus and because of the principle of contacts, connections, cliques, and individuals that connect across cliques and networks, a mere 20% of deer mice are responsible for 80% of the spread. What does this mean in practical terms?
During an outbreak it pays to limit your contacts, avoid attending large events (this connects multiple networks that would otherwise remain unconnected and thereby unaffected- at least temporarily), work from home if possible, etc. That is why those specific WHO and CDC recommendations are being made. It will help slow the spread of COVID-19. This is not permanent but buying time matters. Why? We can discover more about the disease, we can ascertain treatments that work, and ultimately we buy enough time to hopefully develop a vaccine.
If the people in your life are beginning to contract their social networks, don’t make fun or minimize their efforts. They know we can still stay connected digitally, for now, and they are helping to save lives. If elephants can rumble to each other over miles and humpback whales can hear each other 10,000 miles away, I think we can use what we know about social networks and disease transmission to shift our behavior for a few months, help save hundreds of thousands of lives, and give scientists the time they need to developing the medicines and vaccines to protect us all.
And of course, we have the added benefit of being able to wash our hands (though not everyone in the world has access to clean water) and training ourselves to stop touching our face. So, wash your hands, stop touching yourself, and shrink your in-person social network through social distancing as much as possible. Be well!
Some references used in writing this post:
1. Matthew J. Silk, Darren P. Croft, Richard J. Delahay, David J. Hodgson, Mike Boots, Nicola Weber, Robbie A. McDonald, Using Social Network Measures in Wildlife Disease Ecology, Epidemiology, and Management, BioScience, Volume 67, Issue 3, March 2017, Pages 245–257, https://doi.org/10.1093/biosci/biw175
2. Verdolin, Jennifer L., Amanda L. Traud, and Robert R. Dunn. "Key players and hierarchical organization of prairie dog social networks." Ecological complexity 19 (2014): 140-147
3. Nunn, C.L., Jordán, F., McCabe, C.M., Verdolin, J.L. and Fewell, J.H., 2015. Infectious disease and group size: more than just a numbers game. Philosophical Transactions of the Royal Society B: Biological Sciences, 370(1669), p.20140111.