08/29/2025
📊 How Animals See the World
Here, we compare the differences between a jumping spider, an owl, a human, and a pit viper — each creature perceives light and colors in their own way. These differences are due to variations in eye anatomy, umwelt adaptations, and evolutionary pressures that have helped shape each species' visual perception of the world.
The Diagram in the Picture is a visual comparison of a jumping spider, an owl, a human, and a pit viper.
- 🕷 Jumping Spider: Can see from 300–650 nm, including ultraviolet (UV) light invisible to us. Flowers glow like neon signs to them!
- 🦉 Owl: Vision spans 300–700 nm, letting them see in UV and low-light conditions — perfect for nighttime hunting.
- 👤 Human: Our range is narrower (380–740 nm), so we miss out on UV patterns many animals rely on.
- 🐍 Pit Viper: Truly next-level vision. Their eyes detect 320–650 nm, but they also have pit organs that sense infrared heat in the 5,000–30,000 nm range.
🌡️ Snake Heat Vision
Some snakes, like pit vipers, boas, and pythons, have specialized pit organs on their upper labial scales (supralabials). These pits create a kind of heat picture of the world — warm animals glow while cooler objects fade into the background. These pits can detect a temperature difference of 0.001 °C. The nerves that transfer sensory information to the brain route to the optic tectum, which is a major structure in the midbrain that integrates and processes sensory input, particularly visual information. In snakes, the optic tectum functions as the central hub where infrared signals from the pit organs are combined with traditional visual input from the eyes. Specialized trigeminal nerve fibers carry thermal data from the pit organs to the tectum, where these signals are mapped onto the same neural layers that normally process sight.
This integration effectively allows snakes to form a “thermal image” of their surroundings, overlaying heat patterns onto their visual map of the world. In other words, the optic tectum is the region that enables snakes to “see temperatures”—turning heat cues into spatially organized information that guides hunting, navigation, and defensive behaviors.
In the diagram, you can see this represented by the rabbit glowing in oranges and purples, while the flower shines in UV blue.
Sources:
- Brusca, R. C., Moore, W., & Giribet, G. (2023). Invertebrates. Oxford University Press.
- Crowell, H. L., Curlis, J. D., Weller, H. I., & Davis Rabosky, A. R. (2024, June 18). Ecological drivers of ultraviolet colour evolution in snakes. Nature News. https://www.nature.com/articles/s41467-024-49506-4
- F. Harvey Pough, R. M. A., Martha L. Crump, Alan H. Savitzky, Kentwood D. Wells, &. Matthew C. Brandley. (2016). Herpetology. Sinauer Associates, Inc.
- Goris, R. C. (2011). Infrared organs of snakes: An integral part of Vision. Journal of Herpetology, 45(1), 2–14. https://doi.org/10.1670/10-238.1
- Katti, C., Stacey-Solis, M., Coronel-Rojas, N. A., & Davies, W. I. L. (2025, September 5). The diversity and adaptive evolution of visual photopigments in Reptiles. Frontiers. https://www.frontiersin.org/journals/ecology-and-evolution/articles/10.3389/fevo.2019.00352/full
- Scott Freeman and Jon C Herron. (2014). Evolutionary analysis. Pearson.
- Visual pigments, ocular filters and the evolution of snake vision | molecular biology and evolution | oxford academic. (n.d.). https://academic.oup.com/mbe/article/33/10/2483/2925599
- Zou, D., Huang, S., Tian, S., Kilunda, F. K., Murphy, R. W., Dahn, H. A., Zhou, Y., Lee, P.-S., & Chen, J.-M. (2024). Comparative genomics sheds new light on the convergent evolution of infrared vision in snakes. Proceedings of the Royal Society B: Biological Sciences, 291(2027). https://doi.org/10.1098/rspb.2024.0818
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