Polarised Moonlight Navigation in Nocturnal Bull Ants

A groundbreaking study conducted by scientists at Macquarie University in Sydney has discovered that two nocturnal bull ant species, Myrmecia pyriformis and Myrmecia midas, utilize polarised moonlight for navigation. This discovery marks only the second instance of an animal using polarised moonlight to orient itself, with the first being the dung beetle.

Understanding Polarised Light

• The sun and the moon emit unpolarised light, which becomes polarised when scattered by the Earth's atmosphere.
• Polarisation denotes a specific orientation of the electric field, and both sunlight and moonlight, when scattered, create linearly polarised light.
• This scattered light forms an e-vector pattern in the sky, which functions as a natural compass for animals capable of detecting it.

Research Methodology

• Researchers created linearly polarised light and cast it on nocturnal bull ants in their natural habitat.
• The study involved tracking the ants' ability to orient themselves relative to two nests located over 50 meters apart.
• Under different lunar phases, the researchers rotated the polariser to observe changes in the ants' navigation paths, thereby measuring their response to altered e-vector patterns.

Key Findings

• Ants used polarised moonlight throughout the lunar cycle, even when moonlight was 80% less intense during crescent phases.
• Shift magnitudes varied across lunar phases, with higher magnitudes during waxing phases compared to waning phases.
• At Nest 1, ants had greater shift magnitudes due to the longer distance to the foraging tree compared to Nest 2. This highlighted the reliability of the sky compass over long distances.

Scientific Implications and Future Research

• The study draws parallels between solar and moonlight polarisation navigation in ants and highlights the need for further research to explore if ants use additional cues like the panorama or time-compensated lunar compasses.
• Future investigations may consider whether ants can track the moon's position by blocking or exposing access to the sky and familiar surroundings.

This study advances the understanding of navigational mechanisms in nocturnal animals, providing insights that could influence future research in sensory biology and animal behavior.