{"id":3848,"date":"2026-09-22T13:12:15","date_gmt":"2026-09-22T13:12:15","guid":{"rendered":"https:\/\/metamorphosis-project.org\/?p=3848"},"modified":"2026-09-22T13:20:15","modified_gmt":"2026-09-22T13:20:15","slug":"creature-of-darkness-vs-creature-of-light-who-hunts-best","status":"publish","type":"post","link":"https:\/\/metamorphosis-project.org\/fr\/editions-2\/creature-of-darkness-vs-creature-of-light-who-hunts-best\/","title":{"rendered":"Creature of Darkness vs. Creature of Light: Who hunts best?"},"content":{"rendered":"

Do you remember when we filmed prey-capture sequences of olms and Pyrenean brook newts at the Moulis Laboratory Cave<\/a> ?<\/p>\n\n\n\n

Thanks to Noah Heier, a Master\u2019s student who joined us for his internship, we were able to analyze the Pyrenean brook newt dataset and complement it with a series of new experiments. I\u2019m very happy to share the main findings of this work, which have just been published in the Journal of Experimental Zoology Part A<\/em><\/a>.<\/p>\n\n\n\n

Living in a Cave: The ultimate survival challenge<\/strong><\/h3>\n\n\n\n
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Caves are extreme environments, with no light, high humidity, and limited food. These conditions impose strong selective pressures on organisms. As a result, many cave dwellers, such as the olm<\/a>, have evolved remarkable traits, including loss of eyes, depigmentation, and a low resting metabolic rate. But how does adaptation to cave life begin?<\/strong> The Pyrenean brook newt is ideal to understand the initial stages of adaptation of adaptation to life underground. This salamander has two genetically distinct morphotypes: one living in surface streams and the other in cave streams, yet they show no obvious morphological differences.<\/p>\n\n\n\n

So, we took this opportunity to test whether cave-dwelling and surface-dwelling populations differed in their ability to locate prey and in their feeding movements. We tested them both under their usual hunting conditions (darkness for cave dwellers and light for surface dwellers) and under the conditions experienced by the other population (light for cave dwellers and darkness for surface dwellers).<\/p>\n<\/div><\/div>\n\n\n\n

The food-finding race: an escape game in a Y-maze<\/strong><\/h3>\n\n\n\n
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To complement our kinematic data, we used a Y-maze to test whether prey-finding ability and exploratory behavior differed depending on population origin and light conditions. The maze consisted of a circular open area connected to two tunnels positioned at a 45\u00b0 angle from each other. At the end of one tunnel, we placed a tea bag filled with bloodworms, while the other contained a similarly sized and shaped stone. The position of the food was randomized between the two tunnels. Each salamander was then placed in the maze and its behavior was recorded for 15 minutes. Individuals from each group were tested 10 times.<\/p>\n\n\n\n

As expected, salamanders generally spent more time in the area containing food than in the other areas. By contrast, although cave-dwelling individuals are used to hunting in complete darkness, our prediction that they would be faster at detecting prey was not supported. Under both light and dark conditions, the time needed to locate the prey did not significantly differ between cave- and surface-dwelling salamanders tested under the same conditions. <\/p>\n<\/div><\/div>\n\n\n\n

Instead, the differences we observed were more strongly associated with light conditions than with population origin. Under light conditions, both cave- and surface-dwelling salamanders showed more exploratory behavior: they entered the tunnels more frequently and spent more time inspecting the stone area, likely because they could use vision to explore their surroundings.<\/p>\n\n\n\n

Lastly, when salamanders were tested under the light conditions of the other population, we observed some interesting behavioral responses. Surface-dwelling salamanders tested in complete darkness spent more time in the food area and stayed close to the prey for longer after finding it than when tested in the light. This could indicate that, when vision was unavailable, they relied more strongly on other senses, such as smell, to detect and locate food. Interestingly, cave-dwelling salamanders tested in the light also showed a distinct response: they were the only group to preferentially enter the food tunnel first. In all other groups, the first choice did not differ from random.<\/p>\n\n\n\n

Together, these results suggest that both cave- and surface-dwelling populations can adjust their behavior depending on the sensory information available to them.<\/p>\n\n\n\n

The Salamander’s guide to hunting with or without light<\/strong><\/h3>\n\n\n\n

In our previous blog post, we showed a prey-capture video in real time<\/a>. Bellow, you can watch the same behavior in slow motion.<\/p>\n\n\n\n

Pyrenean brook newts use suction feeding to capture prey. This aquatic feeding strategy relies on the rapid expansion of the buccal cavity, which generates a flow of water that draws the prey into the mouth. However, their suction-feeding behaviour varied with lighting conditions.<\/p>\n\n\n\n

In the light, when newts could see their prey, they tended to adopt a \u201cram\u201d behaviour. They lunged towards the prey using their forelimbs and tail, opening their mouths only when they were close. This movement allowed them to generate compensatory suction as they approached their prey. <\/p>\n\n\n\n

In the dark, when they could not see their prey, they instead preferred a \u201cstatic\u201d behaviour. They positioned themselves just above the prey, with a lower head angle, and relied mainly on inertial suction to capture prey directly in front of their mouths. By positioning their mouths close to the surface, they may also have benefited from wall effects, which have been shown to enhance suction performance.<\/p>\n\n\n\n

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