How Ant Colonies Construct and Maintain Nests

Nests can be found in many forms in nature and serve different purposes such as shelter, storage, and regulating the local environment. Among the various types of nests, those built by social insects, like Ants, are especially interesting. These nests are complex, both in how they are built and how they function. Ants make their nests by Digging into the ground or modifying their surroundings. Their nests can be found in trees or underground.

Previous research has shown that the structures of these nests form through the interactions between individual ants and their environment. This process happens without a central leader, demonstrating how living things can organize themselves naturally.

#Research Focus

Most past studies on how ants build nests focused on established groups of ants and looked at short time periods. These studies found that in ant groups of a certain size, the volume of the nest grows in a predictable way as the population increases. This led researchers to think that ants can notice how crowded their nest is and can change how much they dig based on this. This idea may work in smaller ant groups with simpler nests, but in larger, more complex nests, where ants gather in specific areas, it is less likely that ants can assess how full the nest is. In these cases, digging may be increased by bringing in more ants from nearby areas or through factors like humidity or scent.

Ant Colonies have ants of different Ages. It is known that as ants grow older, they will change the jobs they do. However, it is unclear which age groups help with digging in a developing colony. Ant colonies also have different types of ants, including those that reproduce and those that work, and these types can share tasks among themselves. The makeup of the colony is important when considering how a nest develops.

One way to look at ant nests is to think of the colony as a single unit. In this view, the nest acts like a skeleton for the colony. Inspired by how bones grow and heal, we wanted to understand how the size of an ant nest is managed during normal colony growth and after it has been damaged. We focused on a few main questions:

1. How does a colony maintain the growth of both the population and the nest as it changes from a single queen to a larger group?
2. How does a colony recover the size of its nest after it has been damaged?
3. Which ants are involved in digging, and does this differ in the two cases mentioned above?

To answer these questions, we conducted two sets of experiments using a specific type of ant, Camponotus fellah. The first experiment, called "Colony-Maturation," looked at how colonies grow from a single queen to a fully developed colony. We monitored these colonies over a long period of time. The second experiment, "Fixed-Demographics," examined digging by a set group of ants of a known size and age, letting us see how they recover their nest size after a collapse and explore which age groups were involved in digging.

#Nest and Experiment Setup

All the experiments took place in two-dimensional nests made from Plexiglass. The sizes of the nests were measured in terms of area, which could be converted into volume using the thickness of the setup. We created two types of digging experiments: one that tracked how nests were dug over time as colonies grew, and another that focused on digging by specific groups of ants.

#Experimental System and Nest Architecture

We used large nest frames filled with fine sand and ensured that they were kept moist to help with structure. Water moved through the sand, keeping it wet and firm. Each experiment started by introducing a single mated queen and a few pupae into the nest. This allowed us to observe how the nest was dug and how the colony grew from the very beginning. The experiments continued until the queen died or got stuck after a collapse.

The second type of experiment focused on ant groups of a specific size. We tracked the ages of workers over ten months and used varying numbers of young and old ants to see how they dug in the setup.

#Growth of Ant Colonies and Nests

The first series of experiments allowed us to see how both the ant colony and the nest grew at the same time. In all cases, we observed that as the number of ants grew, so did the size of the nest. Initially, the founding queen did most of the digging. Once workers began to emerge from their pupae, she stopped digging. However, the first workers may not have dug much because there were few ants at the time. As more workers appeared, the nest size increased, but the amount of growth varied among different nests.

During this period, as population size increased, the total area dug also rose. We noticed a pattern where the initial growth of the ant population was followed by changes in nest digging, suggesting that the size of the nest was directly affected by the number of ants present.

#Age and Nest Excavation

During the experiments, it became evident that different age groups of ants play different roles in digging. In situations where ants of similar ages were tested, younger ants tended to dig more than older ants. This difference became clear when we looked at how much area was dug based on their ages. Young ants were found to create larger nest areas compared to older ants.

After reaching a stable size, we induced a collapse in the nests to see how ants would respond. We found that after a collapse, ants of all ages began digging to recover lost space, but they stopped once they reached a certain area.

#Age Influence on Digging

Overall, our findings showed that younger ants are more inclined to engage in digging tasks, while older ants contribute less. This idea challenges previous thoughts that only the ants’ physical differences determined their task roles in the colony. Instead, our results indicate that younger ants primarily handle regular nest expansion.

#Nest Structure

The structures of the nests created in our experiments differed based on whether the colonies were maturing or based on fixed groups of ants. In maturing colonies, nests often had large chambers at the top, which served to increase the space available for the growing population. These chambers were filled with tunnels that branched out, making it easier for ants to move. In contrast, fixed-demographics experiments led to nests that lacked such large chambers, likely due to the absence of young ants and the queen.

The orientation of the tunnels also varied. In maturing colonies, tunnels tended to be at a slant, while older colonies showed tunnels angled more straight down. This reflected the age of the digging ants and their digging habits.

#Group Size and Behavior

The size of the ant group plays an important role in how colonies operate. Groups of different sizes have different styles of finding food, sharing tasks, and communicating. However, not much is understood about how behavior shifts during the period right after a colony starts to grow. A rising colony may show distinct changes in behavior compared to a fixed group of ants.

Most existing studies on how ants dig into their nests have been short-term and focused on fixed sizes of ants. Our long-term studies helped us identify many differences in how nests are constructed in normal conditions compared to emergencies.

#Key Findings

#Ants Control Their Nest Size

Ant colonies manage their nest size in relation to the number of ants living in them. When new ants join, the overall area of the nest grows, but younger ants carry out most of the digging. In situations where the nest is damaged or requires rapid expansion, ants of all ages may help in the excavation.

#Differences in Nest Architecture

Nests built in a normal context have larger volumes and different structures compared to those built under emergencies. A well-developed nest indicates the history and experiences of the colony, showing how past conditions have shaped its architecture.

#Age-Dependent Digging

The age of the ants affects how much they will participate in digging tasks. Younger ants tend to dig more and create larger spaces, while older ants do less digging. This indicates that age is a significant factor in how tasks are divided among ants in a colony.

#Conclusion

In summary, the makeup of an ant colony has a crucial impact on how nests are built and maintained. The roles that different age groups play in digging, as well as the overall development of nest structures, shed light on how ant colonies function together. Age-based responsibilities within the colony highlight their remarkable ability to adapt their roles based on experience, ultimately shaping their living environment. Understanding these dynamics provides deeper insights into the intriguing world of social insects and their nesting behaviors.