A marmot sees an eagle circling above the prairie and lets out an alarm call to warn others before hiding. A sparrow hears a cat climbing the tree its perched on and takes off to fly to safety. Other birds seeing its movement are alerted of the threat and take off as well. Both of these are examples of social information about a predator — one passed on intentionally and the other unintentionally. Social information is any information — such as the presence of a predator or a good foraging spot — that an animal makes publicly available (intentionally or unintentionally) to surrounding animals (of the same species or different species).
A marmot sounds an alarm call (wiki)
Ecologists have extensively studied how animals intentionally and unintentionally share social information with each other and how this information moves through the environment, but little is known about how this information impacts overall survival of populations. Does social information have a large impact on the survival of species? How does social information shared across species impact competition between species? To answer these questions, in a new study called “Social information drives ecological outcomes among competing species,” M. A. Gil and colleagues used mathematical modeling to understand the growth and survival of populations with differing levels of predation and social information.
Most importantly, the researchers found that social information can have a large impact on the survival of populations from extinction. Populations with strong social information can survive even when predation rates exceed population growth rates, a circumstance that would usually lead to extinction. In addition, they found that social information can allow populations to reach sizes that otherwise would not be sustainable do to limited resources. The research team found that these effects were particularly prevalent in small and medium sized populations. This has important implications for animal conservation because endangered species have small population sizes, and suggests that animals that use lots of social information may be able to survive in seemingly dire situations.
In addition, the scientists looked at how social information shared between two species that are competing for resources impacts their relationship. Does it allow them to coexist or does it heighten the competition? The answer — it turns out — is it depends. Specifically, it depends on the level of within-species information sharing versus the level of between-species information sharing. In systems where within-species information dominates, one species tends to dominate over the other — only one of the species can survive in a given location. On the other hand, when between-species information sharing is more common, the species are usually able to coexist. In fact in some cases, growth in the population of one species may help the other species survive. This type of situation may seem unlikely to occur in nature, but there are actually many situations when animals rely more on signals from other species than from their own species. For example, in tropical regions, birds often travel in mixed-species flocks instead of sticking to same-species groups. This study confirmed the importance of social information to the survival of species that live in these types of groups.
