Temperature stress on ants: can behaviour mitigate consequences for colony survival.

By 11/22/2021Current Projects
HSF 21047 | Amount: $67,000 | Project Leader: T Ord | Project Period:

A project undertaken at the University of New South Wales, and supervised by A/Prof Terry Ord.

The large, bustling nests and manicured foraging highways of the meat ant are a familiar sight to many Australians. Ecologically, meat ants dominate invertebrate communities in many areas of eastern Australia and are key players in the seed dispersal of many plants. Like other ectotherms, we know meat ant behaviour is temperature-dependent. Thermal tolerance of meat ants has also been examined in the context of the predicted temperature changes under climate change.

However, past work has focused on the extreme physiological temperatures that can be tolerated by meat ants before incapacitation occurs in the laboratory. This ignores that ectotherms actively regulate their behaviour in the wild to mitigate temperature effects on physiology. In the case of meat ants, this type of behavioural ‘plasticity’ takes two forms.

First, at the level of individuals, the temperatures at which meat ants voluntarily emerge from the nest to swarm or forage is a decision that balances the benefits of defence and resource acquisition against the physiological costs of that activity at extreme temperatures. Second, at the level of the nest, colonies attempt to establish new nests in order to escape adverse microhabitat conditions in a phenomenon known as “stress bolting”. This is analogous to bolting in stressed plants that produce runners or “go to seed” in an attempt to establish in areas more favorable for growth.

This project will document these behaviours in the meat ant in order to evaluate the extent to which behaviour can buffer the colony from both short-term (e.g., seasonal) and long-term (e.g., prolong climatic conditions) temperature stress. It will do so by measuring the impacts of temperature on the emergence and foraging behaviour of individual workers, and experimental manipulations of the temperatures experienced by whole nests through shading and heat exposure treatments, to determine the conditions under which nest bolting is induced.

The project will enable a direct link to be drawn between the consequences of temperature stress on the behaviour of individuals, and how this impacts the placement and survival of meat ant nests, and ultimately what the likely response of this species might be to environmental change. The project will also provide foundational data for assessing the extent to which we can expect ectotherms to mitigate the impacts of raising temperatures through thermoregulatory behaviour.