Creating a prairie dog “Facebook” to aid conservation
Animal behavior researchers have long been interested in the social dynamics of social species, but the traditional tools of field observations typically limit researchers to fairly rudimentary descriptions of social groupings. If two individuals have repeated negative interactions, then they’re not members of the same social group; if they feed at the same time in close proximity to each other, then they are probably members of the same social group. More recently, however, biomathematicians have increasingly used “social network analysis” or SNA to reveal more complex features of animals’ social lives. But it has not yet become clear whether the two methods reveal similar patterns, perhaps with SNA including more nuance or complexity, or whether they reveal different sorts of patterns, which would suggest that they describe different forms of social interactions.
North Carolina University researchers Jennifer L. Verdolin, Amanda L. Traud, Rob R. Dunn turned to Gunnison’s prairie dogs to directly compare SNA with the more traditional approach.
Gunnison’s prairie dogs are highly social ground squirrels that live on the grasslands of the Colorado Plateau, which spreads into neighboring Utah, Arizona, and New Mexico. They’re large for squirrels, measuring over a foot in length when fully grown and weighing up to a kilogram. They’re also important vectors for the spread of bubonic plague. Verdolin, Traud, and Gunn’s research, published recently in the journal Ecological Complexity, provides a more nuanced understanding of the squirrels’ complex social lives. It will not only allow epidemiologists to better halt the spread of the disease, but will also allow conservation biologists to better plan their conservation initiatives.
Each prairie dog colony – the researchers focused on three distinct ones – contains some 60 to 200 individuals, but the colonies themselves are broken into social groups of between three and fourteen individuals, each with their own unique territories.
Overall, the two approaches produced similar results, grouping each individual prairie dog into the same social groups. Where SNA became more useful, however, was in uncovering sub-groups, and in identifying individuals who played particularly critical roles in group dynamics.
Some prairie dogs served as “hubs,” for example, which meant that they had relationships with more individuals than was the average for their group. For example, in the “Country Club” colony (see below), individuals 30, 31, and 32 had relationships with 9, 9, and 8 other prairie dogs, respectively, which is far higher than the group average of 4.
Other individuals served as “bridges,” linking two distinct groups. In the “Country Club colony,” individuals 17, 25, 27, and 30 served that role. The measurement that describes the degree to which an individual serves as a bridge is called “betweenness centrality,” and it was 168, 180, 194.8 and 171.5 for those four individuals, respectively, compared with a group average of 29.37.
The most complete picture came when considering both traditional and mathematical approaches, side by side. For example, while all prairie dogs 17, 25, 27, and 30 were all identified as bridges by the SNA approach, the researchers realized that 25 and 27 were acting as “temporary bridges,” while they transitioned from one social group to another, which 17 and 30 were relatively more permanent in their bridge positions.
“Prairie dogs are increasingly rare and are subject to bubonic plague,” said Verdolin, a researcher at NESCent, in an official statement. She thinks that this research “could help us find ways to mitigate the spread of plague [and also to] understand how these social groups are connected, so we can limit the disruption to prairie dog populations when we need to relocate them for conservation purposes.”
When it comes to disease transmission, hubs ostensibly serve to accelerate the spread of a pathogen within a group, while bridges move it between groups. Removing those individuals from their groups, or treating them as soon as they become infected, would be one way to inhibit the spread of the plague.
In addition, a more complete understanding of prairie dog sociality would allow conservationists a higher likelihood of success when relocating colonies. By relocating entire social groups, rather than arbitrarily splitting them up, researchers might improve the animals’ chances of colonizing a new environment. After all, as psychologists have known ever since Harry Harlow gave infant monkeys a choice between a cloth monkey and a wire monkey, social animals need a lot more than basic nourishment to survive. They need their friends and family. – Jason G. Goldman | 30 July 2014
Source: Verdolin J.L. & Robert R. Dunn (2014). Key players and hierarchical organization of prairie dog social networks, Ecological Complexity, 19 140-147. DOI: http://dx.doi.org/10.1016/j.ecocom.2014.06.003
Header image: Carnat Joel/Flickr
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