We have a few publications accepted in the last few months. Two of which that are currently available are about the crepuscular-nocturnal bull ant, Myrmecia pyriformis.
In one story (1), with Sam, Bob and Jochen, we documented the nocturnal foraging style of these Myrmecia ants. It turns out that majority of ants from each nest carry out just one trip per day (technically night), starting close to sunset and ending around sunrise time. The few (<10% of the forager force) who make multiple trips are the ones that return with prey. The others seem to return with some form of food (most likely honeydew, sap). We determined this by weighing individual ants before and after foraging. We found an increase in body weight of individuals returning without prey – about 13mg on an average for an ant weighing 95mg, which is quite substantial. Those individuals that carry out only one trip seem to be the non-hunting ants.
So, this provided a natural spread of the times at which animals return home: those with prey return at night, some return during sunrise, thus experiencing a wide range of light intensities under which they need to navigate.
In the second study (2), with Chloé and Sam, we addressed how the navigational efficiency of these ants change at different light intensities. As it gets darker, ants stop longer and more frequently while foraging. This allows them to capture more light to create a brighter but coarser view of the world, which gives them enough information to head in the right direction for a short distance. At low light conditions they have huge problems in navigating to the nest and especially in pinpointing the inconspicuous nest entrance. Often, ants walk right on top of their nest entrance and continue to spend several more minutes searching for the nest entrance. At bright light intensities they walk faster and are most accurate in locating the nest. So despite being strictly crepuscular-nocturnal their navigational efficiency suffers at low light conditions. This indicates that (a) nocturnal bull ants are visually guided even at low light conditions, (b) most foragers avoid navigating at night because they are really bad at it and hence restrict their navigational tasks during dim lit periods of twilight.
1. Reid SF, Narendra A, Taylor RW & Zeil J. 2013. Foraging ecology of the night-active bull ant, Myrmecia pyriformis. Australian Journal of Zoology 61: 170-177.
2. Narendra A, Reid SF & Raderschall CA. 2013. Navigational efficiency of nocturnal Myrmecia ants suffers at low light levels. PLoS ONE 8(3): e58801.