Constructing the social network of California Condors
Here at Condor Watch, we are using the data we glean from the feeding stations to ask many different questions that will help us better understand the ecology of California Condors. One of the major goals of Condor Watch is to understand how individual condors feed together. Using the identities of tagged individuals in photos, we can begin to construct the social network of California Condors. When you hear “social network”, you probably think of Facebook, Twitter, etc. And in effect, we are trying to building the “Facebook of Condors”. That is, we’d like to know which condors are “friends” that feed together, and potentially lead each other to feeding sites.
By combining information about individual histories of lead poisoning and the social network across time, we hope to understand how social relationships might affect the spread of lead poisoning through the population. We hope that this type of analysis will reveal important pieces of the puzzle for mitigating the effects of lead poisoning in this highly endangered species.
How things spread through social networks
The study of social networks originated at the intersection of sociology and mathematics, but it has increasingly become an important tool for ecologists as well. These studies have shown us how “social contagion” can facilitate the spread of all kinds of things–behaviors, ideas, germs, etc. Thus, understanding the structures of the social networks in which we live can help us who smokes or gains weight, or how we think and feel (see this TED Talk by Nicholas Christakis for a summary).
What do we know about social networks in animals? There has been an explosion of recent research investigating this question, and the results have been fascinating. For example, studies of animal social networks have shown that unique foraging strategies spread through social networks in monkeys, birds, as well as whales. Social networks are also important to the spread of diseases that are threatening animal populations around the world. For example, network structure can help explain how facial tumor disease spreads in Tasmanian Devils.
How to build the social network of California Condors
So, how can we apply these ideas about social networks to understand the dynamics of lead poisoning in California Condors? THIS IS WHERE WE NEED YOUR HELP! With your efforts in identifying individual birds in our photographs, we can start to piece together the social network of condors. Here is a little example of how this works:
Let’s say you saw these 5 photos…
From these photos, we can start to build a social network. It might look something like this:
Here, each circle, or “node” represents an individual condor, and the lines connecting them represent their propensity to feed together. Thus, individuals 3 and 12 are connected by a thick line because they always feed together (whenever 3 is seen, 12 is also there). We can already start to see some features of this hypothetical social network. For example:
- There are two clusters of individuals that often feed with each other (3, 6, and 12 vs. 31 and 5).
- Individual 14 feeds sometimes with both clusters–she is a “connector” of social clusters.
And these two patterns can have implications for the spread of lead poisoning if these social relationships turn out to be important. Say #31 and #5 find a lead-laden carcass and get lead poisoning. But is individual #3 likely to also get lead poisoning from this carcass? This might depend in part on #14–if she learns where the carcass is from #31 and #5, then this information might get passed on to the others more rapidly. This is the importance of the “connector” or “social broker”–she facilitates the spread of information across the entire network, and this might be the key to understanding who gets poisoned and why.
In truth, we do not yet know whether lead poisoning spreads this way–this is just one hypothesis. The first step is to get these valuable data from the photographs we have and start understanding what the “Facebook of Condors” looks like. This is one way in which your efforts on Condor Watch will help in the larger goal of conserving these magnificent birds. We greatly appreciate your help!!
Integrating other data
The social network analysis is only one of many datasets and analytical tools we will be using to help conserve these majestic birds. From the photographs, we will also be looking at other social dynamics such as social dominance–e.g., are dominant or subordinate birds more susceptible to lead poisoning? For some birds, we are also collecting detailed data on their home ranges using GPS units mounted on their wing tags (you can sometimes see these in the photos). Ongoing studies on physiology and toxicology of lead poisoning are key to understanding the impact of lead on an individual level (see this previous post). These and other data sets will ultimately be used to better understand what factors help or hinder the recovery of the condor population. A really exciting aspect of the Condor Watch project is that it is a true collaboration between behavioral ecologists, spatial ecologists, ecotoxicologists, population ecologists and citizen scientists!
We will continue to post more tidbits on our scientific plans and progress, so please keep checking back!