Homeward bound

Ants need to find their way home, too. Trevor Murray is reconstructing the visual cues that they use to navigate back to the nest.

 
 Illustration by Leigh Douglas

Illustration by Leigh Douglas

 

Ethograms is a monthly column published in collaboration with the Australasian Society for the Study of Animal Behaviour (ASSAB), showcasing the work of early-career researchers. Dominique Potvin is a postdoctoral researcher at the Australian National University, and an outreach officer for ASSAB.

We've all had the experience of getting lost while walking a seemingly familiar path.  Your mind has wandered for only a few minutes, and, as you snap yourself back to reality, you look around to see nothing but unfamiliar surroundings. Most likely for us, a smartphone is close at hand and any initial panic is short-lived: we can simply turn on the GPS and let a mapping application guide us home.

Animals do not have this same luxury. So what do you do if you are a small insect — such as an ant on a foraging expedition — that has been displaced? How do you find your way home?

There are a variety of methods that ants use to navigate through their landscapes. Olfactory cues such as pheromone trails can be useful for some species. Alternatively, short-term memorisation of vectors (directions) and relative distances can help others simply "retrace their steps" back to the nest. But different landscapes, cognitive and sensory abilities call for different strategies. And one strategy that appears to be particularly important is using visual cues to point an ant homewards.

Trevor Murray, a postdoctoral scientist at the Australian National University, is part of a team of researchers — including Jochen Zeil's lab at ANU and Ajay Narendra's lab at Macquarie University — trying to figure out how such a small animal might utilise such seemingly complex information.

 
  Researcher Trevor Murray is trying to understand how ants navigate back to their nest.  © Trevor Murray

Researcher Trevor Murray is trying to understand how ants navigate back to their nest. © Trevor Murray

 

Research completed by Murray and his colleagues in 2014 showed that the visual scene is very important to insects that forage from a home base, such as a nest or hive. Ants, bees and wasps initially perform specialised "learning" flights or walks around this base, presumably gathering images and memorising views of their nest from many different positions and compass directions.

"When we displace experienced forager ants to places they have never been before as much as 10 metres away, they look around briefly and then walk straight back to their nest,” says Murray. “We want to know what information they are using to perform this feat".

Murray uses 3D reconstructions to compare panoramic views taken at different locations around the nest. The further from the nest, the more different these views are from one another, but nearby features such as trees can provide commonality among scenes that might otherwise be indistinguishable. Ants can use these differences to guide themselves back to the panorama they remember from their initial learning walks around the nest. But how difficult this journey is will depend on the environment. The complexity of a surrounding nest landscape holds a lot of information that insects can use to navigate. However, there are a few stumbling blocks in understanding how individuals are processing so much information.

 
  A digital reconstruction of the visual cues that an ant might use to navigate home.  © Trevor Murray

A digital reconstruction of the visual cues that an ant might use to navigate home. © Trevor Murray

 

After displacing ants from their normal foraging path, Murray places them on a trackball, a sort of 360-degree ant treadmill. "Although they are mostly very good at moving on the ball and finding the correct path home, they appear to ignore the fact that they are essentially running on the spot,” he says. In other words, vision appears to be so important that it essentially overrides other senses when it comes to making navigational decisions. 

To dig deeper into this question, Murray is also helping PhD student Zoltán Kócsi build an entire virtual reality system — dubbed the ‘Antarium’ — that surrounds the trackball, recreating an ant's visual landscape catered to its own visual system. This technology is cutting-edge, and allows full control of what the insects see.

"By reconstructing their natural environment, and then projecting it back at them using a game engine, we will be able to manipulate any detail we see fit,” says Murray. “This will hopefully allow us to push the neural processing of these insects to breaking point so that we can understand exactly how they are representing and using visual scenes".

 

Ant movements are delicately recorded using a trackball. Video: Ajay Narendra

 

But, like all new technology, it presents many challenges. From trying to integrate ecological data into games programming, to engineering a fully-functioning insect-sized virtual reality complete with moving platform, the ‘Antarium’ certainly requires a high level of skill, patience and dedication.

"We are integrating techniques from many different disciplines to create something wholly new,” says Murray. “[It] is a lot of work and takes a long time, but our team is getting pretty close and we can’t wait to see how the insects respond once everything is up and running".

It is his hope that by understanding how insects navigate, we can not only understand more about neural processing in general, but also apply this knowledge to designing algorithms that allow for autonomous movement — by, say, drones or other robots — through a complex landscape.

Edited by Andrew Katsis and Ellie Michaelides