Guest blog from Samuel Ellis, a PhD student at the University of York Centre for Complex Systems Analysis
There are an estimated 22,000 species of ants, and it is likely that the weight of ants on the planet is greater than the weight of humans. They are very important to ecosystems all over the world including in this country. I am currently conducting a study on the hairy wood ant (Formica lugubris) at the Longshaw Estate in the Peak district. This species is part of a closely related group of six species called the red wood ants which dominate woodland environments across Europe.
These ants build distinctive dome shaped nests of pine needles (with underground chambers) which can be up to 1m high (but are more usually around 30cm). They are apex invertebrate predators outcompeting other ant species and hunting for invertebrate prey on the forest floor and in the tree tops, ranging from flies to earthworms. However, the main food source of the colonies are ‘aphid farms’; colonies maintain herds of aphids in the canopy which they milk for honeydew, a sugar rich by-product of aphids feeding on tree sap.
I am studying how their nesting behaviour influences their foraging. A single hairy wood ant colony can have many nests, so workers and queens (wood ants often have multiple queens in a single colony, this is quite common in ants) are spread through the nests, they exchange workers and brood (eggs, larvae and pupae) between the nests and there are constant ‘trails’ of ants walking between the nests forming a network. Interestingly this multiple nests behaviour (called polydomy), though usually present in this species in the UK, is never found in the same species in Finland or Switzerland.
I’m interested in how the ants use this nesting network to take advantage of the environment: what evolutionary benefit does it bring them? To this end I’m testing how the ants use these networks to exploit their environment.
If the colony is given extra food near one particular nest (in the form of sugar solution to mimic honeydew) do foragers from other nests move through the network to take advantage of the food bonanza? Or are workers who were formally ‘nest workers’ converted to ‘foragers’? Or does the entire network rearrange? So I’m painting foragers from different nests different colours to see if they move through the network.
This will hopefully give some important information how this ecologically important and charismatic species relate to their woodland environment. For more information on these fascinating species visit the UK Red Wood Ant website.