Student Research Spotlight - Raquel Gontijo de Loreto
Posted: July 3, 2014
With ants and foods, the shortest path isn't always the best
By Arash Maleki
Ants prefer to make their food searching trails on fallen tree trunks rather than the ground, even though this tactic is slower, according to a recent study carried out in rainforests in Brazil. Tree trunks provide a stronger pheromone signal for other ants to follow and less risk of enemies.
"In nature, being faster is more important" said Raquel Loreto, a PhD student of Entomology at Penn State University. Studies in lab always show ants end up choosing the shortest way, yet in the field she found that ants use fallen branches and twigs as bridges to build their trails, which can make the path to the food source longer than a straight way on the forest ground. Although the total searching speed of ants on the bridges is higher than estimated one on the floor.
As the reason the pheromone signal is stronger on twigs is because the more absorbent nature of bark material lessens the evaporation rate of pheromones. The availability of pheromones reduces detecting time and boosts searching speed, in much the same way that Hansel and Gretel’s return home was helped by leaving a trail of white pebbles.
Adding to being lost in the jungle, there are other kinds of dangers persuading ants to climb on trunks. Authors discuss how escaping from fungus contamination and predators shapes the ants searching behavior. Walking on the forest floor increases risk of contact with predators and fungi spores, which ants don't like.
The paper concludes a much complex searching behavior instead of simple tracking habits in petri dishes. Finding more details about this complexity is Loreto's goal for further research. She will focus on distribution of disease in ant population.