Again, complex consequences are emerging: Researchers report that increased temperatures as a result of climate change could increase aggressive behavior between rival ant colonies. This is what observations in an alpine ant species suggest. Animals from colonies in warmer temperature zones of the Alps therefore react more hostile to their neighbors than specimens from cooler regions. If the association exists in other species, it may have ecological significance. The scientists explain that more "wrangling" among ant colonies could have a negative effect on their overall performance.
They are small, but the importance of ants to the world is huge. This was recently impressively reflected in an estimate: According to this, around 20 quadrillion ants crawl across our planet and thus form a huge total biomass. They also often play a central ecological role in their various habitats: They have an important function in the material cycle and have a complex effect on other organisms and the environment through their various activities. Against this background, it seems important to know how these ecological masterminds might react to environmental changes caused by humans.
What factors determine hostility?
The researchers around Patrick Krapf from the University of Innsbruck have now dealt with the possible effects of environmental changes on the behavior of the ants. Specifically, the focus was on intraspecific competition between different colonies of one species. It is well known that individuals from neighboring states can react hostilely when they encounter one another. Previous studies have already shown that elevated temperatures can increase aggressive tendencies in animals, including humans. Using the example of the species Tetramorium alpestre, which is widespread in the Alpine region, the researchers investigated whether this is also evident in ants.
To do this, they recorded the characteristics of the habitat of populations at eight locations at different altitudes in Austria, Italy, France and Switzerland. In addition to the temperature conditions there, the researchers examined the physical and genetic characteristics of the ants. In order to record how hostile or peaceful they react to conspecifics from other colonies at the respective locations, the researchers carried out tests in the laboratory and on site. To do this, they allowed two workers from neighboring colonies to meet each other. "These interactions, recorded on video, were intended to simulate encounters in the wild - as occurs when worker ants search for food," says Krapf. The videos were then evaluated by the team on a second basis and resulted in an average aggression value for all encounters.
More aggressive in warmer zones
As the team reports, the evaluations showed that the ants of some populations attacked each other much more vehemently than others. The comparison with the other recorded data showed that in this species the aggression does in fact correlate with environmental factors. "The aggressiveness of the ants from the warmer areas was increased many times over compared to the cooler locations," says Krapf. However, the researchers found no evidence of a role for genetic factors. However, there was another correlation: "In addition to the increased air temperature, we also observe a connection between the nitrogen content in the workers and in the soil and hostility," says Krapf. This can also be an anthropogenic aspect. "The nitrogen availability in soils is probably also due to the ecological change caused by the climate crisis in soils," says the researcher.
As he and his colleagues emphasize, however, more research is now needed to clarify the precise background of the connections that are emerging in their results. In addition, it remains uncertain to what extent the results can also be transferred to other ant species. But if this is the case, the effect could have ecological significance, explains Krapf: "It is normal for ants to show aggressive behavior towards other colonies when they are looking for food. But if these fighting activities increase, it costs the workers a lot of energy and time. This could have a negative impact on the development of the entire ant colony, because then the number of ants would decrease and, for example, less food would be available." In conclusion, the scientist says with a view to further research needs: "Since ants are very important ecosystem service providers, a better understanding of the consequences of global change is of great importance."
Source: University of Innsbruck, specialist article: Science of The Total Environment, doi: 10.1016/j.scitotenv.2022.160443