Insect-based tourism: glowworms in a show cave give robust bioluminescence displays

Context Waitomo Glowworm Cave in New Zealand receives up to 500,000 visitors per year to view the impressive bioluminescent display of glowworms that use light to lure prey into their webs. Visitors board boats and traverse the glowworm chamber in quiet and darkness. The level of visitation requires active microclimate management including entry door automation and monitoring of partial pressure of carbon dioxide, temperature, and airflow in the cave. Timelapse photographic monitoring of the numbers and intensity of glowworms in the cave began in 2011. A 2024 report described annual and daily cycles in both parameters. A new monitoring camera installed in 2024 has allowed uninterrupted assessment of bioluminescence over a full year. Aims This study aimed to assess whether tourism-related activity has an impact on the display of glowworms. Sources of disturbance could include artificial light, sounds and other vibrations, and airflow in the cave. Methods Photographs were taken at 30-min intervals for 12 months through 2024–2025 and at 5-min intervals for one of those months. Image analysis derived a count of larvae and an estimate of the overall intensity of the display at each interval. The speed and direction of airflow in the cave was monitored at 5-min intervals through the same period. Daily and annual cycles of count, intensity, and airflow were depicted as heatmaps. Key results Exposure to artificial light that frequently occurs at the start of the working day tends to perturb the smooth daily cycle of count and intensity. More variability in the bioluminescence display is seen during the visitor day than when the cave is closed, likely due to brief light disturbance or exposure to vibration or sound from the boats. Conclusions The display intensity is modestly affected by visitation, mostly at the beginning and end of the visitor day but at a level probably undetectable by humans and unlikely to affect the glowworms’ ability to capture prey. Implications The analysis revealed environmental conditions under which the underlying daily cycle can be perturbed during the visitor day and temporary responses to noise or light disturbance. The timing of maintenance or tour activity that results in light or noise in the cave can be scheduled to reduce its impact on the display.