Light cue intensity influence on cue weighting during straight line orientation in Kheper lamarcki

Abstract

Signal integration and cues weighting during orientation in insects is an open scientific question. This study focuses on understanding how dung beetles weigh sun cues of different light intensities. Alongside this, my study also tries to investigate potential behavioral effects of AprilTags application, which has great potential in future studies in this field, on beetles’ orientation. The South African dung beetle species Kheper lamarcki was used to investigate this. The beetles' orientation response was tested under conditions with different light intensities while a cue conflict was introduced. The results show that K. lamarcki are able to use even dim light for orientation, but prefer to use brighter light, giving it more weight. However, the presence of two light cues of similar intensity causes the beetles to fail to orient. These findings are useful for understanding the cue-weighting process in the central complex and may also have practical applications, such as helping to predict the effects of light pollution. AprilTags may also impair the orientation accuracy of these beetles, which needs to be considered in future experiments when being used. Overall, this topic requires more detailed study of weighting mechanisms, but the use of AprilTags may have significant potential if their impact is taken into account.

Popular Abstract

Illuminating the path: Role of light intensity in cue weighing

Monday. You wake up, do your morning routine, and go to work. When you leave your house, you turn right into a small street, walk 100 meters, then turn left and reach the bus stop. The bus takes you through a maze of streets and roads to your destination. Eight hours pass, and you repeat your morning route in the opposite direction to get home again. Without even realizing it, we use our ability to orient and navigate every day. Step by step, as we walk along familiar paths, special neurons in our brains fire in sequence, allowing us to recreate the route we have already traveled from memory, like a map. However, when we arrive in a new place, we need external cues for orientation. Using maps and compasses for this purpose, we give little thought to how other animals navigate and orient themselves.

You have probably heard of many famous examples of migration among mammals, birds, reptiles, fish, and insects. One of the most famous examples is the Monarch butterfly, which makes a migration between the United States/Canada and Mexico that covers up to 4,000 km. Many of them fly this route for the first (and last) time in their lives. So how can these insects navigate in such a large area? They use the sun (both its position in the sky and the polarization pattern of its light), as well as the Earth's magnetic field. However, the ability to use multiple cues at once creates the problem for the insect of choosing the most reliable cue at every moment, which will be given the greatest "weight". This process of cue weighing is key in this work.

Dung beetles are an excellent model organism for studying orientation behavior in insects. They create a ball of dung, and they roll it in a straight line as far as possible from their competitors, which makes it easy to note the direction they have chosen. In this work, to study the process of cue weighing, Kheper lamarcki beetles were placed in an arena with LEDs around it, which was used to simulate light cues. In each case, two sun stimuli were present: one brighter and the other of variable intensity. After the beetles were allowed to roll the ball under these conditions twice, the brighter sun changed its position by 90°, while the other sun remained stationary. The beetles were then allowed to roll the ball twice more, which made it possible to find out how orientation behavior would change in response to the cue rotation, and thus to test which cue (brighter or dimmer) the beetles would give more weight to in their orientation.

Another aspect of this work was also to test the effect of AprilTags on orientation behavior. AprilTags are small square tags that can be easily attached to the beetle’s body and allow for tracking its movements and rotation. Therefore, they have significant potential to be used for future studies of orientation behavior in beetles, but first it is necessary to investigate their potential effect on this behavior. To do this, several identical experimental conditions were created, as described above, which differed in the presence of a tag and its type (paper or plastic).

The results show that beetles are able to use even low-intensity cues for orientation, but they prefer higher-intensity cues. At the same time, the presence of two cues of similar intensity makes it difficult for the beetles to choose the more reliable one and therefore disrupts their orientation behavior. This may be an important factor in further studies of the effect of light pollution on orientation in insects. Research on the effects of AprilTags shows that they can disrupt orientation in dung beetles. And this effect is greater for plastic tags than for paper tags. Nevertheless, these tags have significant potential for further research, and their effect can probably be minimized by reducing mass, area, and reflectivity.

Overall, this work reveals certain aspects of the cue-weighting mechanism and is also important for developing a methodology for studying dung beetle orientation using AprilTags.

Master’s Degree Project in Biology - 30 credits, Department of Biology, Lund University
Supervisor: Marie Dacke, Department of Biology, Lund University

• author: Voityk, Andrii
• supervisor: Marie Dacke
• organization: Degree Projects in Biology
• course: BIOM02 20251
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Biology and Life Sciences
• language: English
• id: 9192966
• date added to LUP: 2025-06-04 15:07:06
• date last changed: 2025-06-04 15:07:06