The Effects of Sound on Reptiles

This is an early version of an article that was published by MCBT in local newspapers.

From a baby’s first cry to thundering cracks of lightning, sound is a powerful force. We may not think about it all the time, but sound affects our world more than we know.

When we think of protecting wildlife, we often think of the physical aspects: hunting bans, habitat protection, ample food sources, clean water. But what about the things we can’t see or easily measure? Noise pollution is one of these issues.

Sound, especially loud, unpredictable, or intense noises, negatively affect animals and cause stress (1). Stress over time can lead to poorer health, faster aging, decreased reproduction, and greater susceptibility to diseases (2). Sound can also interfere with various types of communication like mating and hatching calls. In species that are vulnerable or endangered, this can compound their vulnerability and have major consequences.

Construction is one of the most well-studied sources of sound pollution. In 1989, construction blasting just 2 km from a Nile crocodile farm in South Africa caused the death of 26 young female crocodiles (3). When the blood of crocodiles in control and stressed groups were analyzed, it showed that chronic stress led to higher chances of disease and infection. In a study of the eastern blue-tongued lizard, lizards displayed more time “freezing”, a sign of chronic stress, when exposed to high frequency mining machinery noise (4).

Today, more and more research is being done on unconventional types of noise pollution. Three species of sea turtles: green turtles, flatback turtles, and hawksbill turtles, showed disturbance behaviors in response to drones at an altitude of 20-30 m. Saltwater crocodiles showed a range of disturbance behaviors to the same drones at an altitude of 50 m (5).

In 1972, India passed the Wildlife Protection Act, providing for the protection of wild animals, birds, and plants. The Environmental Protection Act (EPA) came in 1986, to protect and improve the human environment while preventing hazards to humans, other living creatures, plants, and property. In 2000, under the EPA, India passed the Noise Pollution (Control and Regulation) Rules. This created four different categories of noise levels in India, based on if the area is an industrial area, commercial area, residential area, or silence zone. Noise is measured in decibels (dB); continuous noise in excess of 90 dB can cause loss of hearing in humans and changes in the nervous system (6). In an industrial area, 75 dB is allowed during the day and 70 dB is allowed at night. In a commercial area, 65 dB is allowed during the day and 55 dB is allowed at night. In a residential area, 55 dB is allowed during the day and 45 dB is allowed at night. Finally, in a silence zone, 50 dB is allowed during the day and 40 dB is allowed at night. The day time is from 6:00 am to 10:00 pm, while the night time is from 10:00 pm to 6:00 am.

These limits however may not always be well enforced as India is a country of loud events. 2017 data from the Central Pollution Control Board (CPCB) showed that the average daytime noise level in Chennai exceeded the noise limits across 10 zones 88.8 percent of the time. Night time noise was much worse, with average ambient noise levels exceeding limits 98.8 percent of the time (7). Special events, such as weddings, holidays, or funerals, can be much louder as well and occur across multiple days.

The use of firecrackers during Diwali is one area the government has attempted to crack down on, with restrictions on the type of firecrackers allowed and the times of day they can be set off. Green crackers are the only type of firecrackers allowed, as they produce less dust and sound compared to other traditional firecrackers (8). Activist Sumaira Abdulali of the Awaaz Foundation, however, says that the use of green crackers isn’t enough to reduce noise pollution. Often, green crackers aren’t well-marked or well-regulated, and they can exceed the prescribed limits for noise and air pollution. A test by the Maharashtra Pollution Control Board (MPCB) and Awaaz Foundation prior to Diwali 2019 found that 10 out of 29 firecrackers did not mention chemical composition in their packaging, while only 12 out of 29 mentioned noise limits (9).

In some villages in Tamil Nadu, villagers have not used firecrackers during Diwali for several decades to protect and conserve wildlife. Kollukudipatti, Vettangudipatti, and Krishnapuram village are all close to the Vettangudipatti Bird Sanctuary. They are mindful of the various bird species there and do not want to bother them in any way. Koonthankulam village near the Koonthankulam Bird Sanctuary is the same way- firecrackers, loudspeakers, and drums are all avoided during festivals and events (10). Thoppupatti and Saampatti villages have a “silent” Diwali to protect a local bat population (11).

Actions like these make a big difference, and it is inspiring to see villages and communities coming together to protect their natural environment. When hosting your own events, consider making them “silent” by not bursting firecrackers, keeping doors closed to prevent sound from travelling far, and avoiding the use of microphones and other loudspeakers.


1. Jakob-Hoff R, Kingan M, Fenemore C, Schmid G, Cockrem JF, Crackle A, Bemmel EV, Connor R, Descovich K. Potential Impact of Construction Noise on Selected Zoo Animals. Animals. 2019 Aug;9(8):504.

2. Romero ML, Butler LK. Endocrinology of stress. International Journal of Comparative Psychology. 2007 Dec 31;20(2).

3. Watson P. Effects of blasting on Nile crocodiles, Crocodylus niloticus. InProceedings of the 10th Working Meeting of the Crocodile Specialist Group IUCN 1990 (pp. 240-252).

4. Mancera KF, Murray PJ, Lisle A, Dupont C, Faucheux F, Phillips CJ. The effects of acute exposure to mining machinery noise on the behaviour of eastern blue-tongued lizards (Tiliqua scincoides). Animal Welfare. 2017 Feb 1;26(1):11-24.

5. Bevan E, Whiting S, Tucker T, Guinea M, Raith A, Douglas R. Measuring behavioral responses of sea turtles, saltwater crocodiles, and crested terns to drone disturbance to define ethical operating thresholds. PloS one. 2018 Mar 21;13(3):e0194460.

6. Environmental Education Centre. Environmental Laws of India.

7. Central Pollution Control Board. Status of Ambient Noise Level in India 2017. 2018 Aug 23.

8. Kandavel S, Sundar S. “Green crackers: Short on sound and light, high on confusion”. The Hindu. 2019 Oct 20.

9. Telang S. “NGO: Green crackers fail to curb noise pollution”. The Asian Age. 2019 Oct 19.

10. Kannadasan A. “Bye bye crackers, hello birds”. The Hindu. 2019 Oct 24.

11. Abraham B. India Times. 2019 Oct 24.

Naomi is serving as an American India Foundation (AIF) Clinton Fellow with the Madras Crocodile Bank Trust (Croc Bank) in Mamallapuram, Tamil Nadu. For her Fellowship project, she is designing educational material and activities for youth and adults to learn about India’s ecosystem and to promote the conservation of endangered species in their natural habitats. Born in Taipei, Taiwan, and raised in Portland, Oregon, Naomi recently graduated with a degree in organismal biology and ecology. While at Colorado College, Naomi worked for the Office of Sustainability, overseeing various green certification programs and serving on the Campus Sustainability Council. She also worked as a lab technician in the GIS (Geographic Information Systems) Lab and as a resident advisor. She completed over 300 service hours through the Community Engaged Scholars program, was a backcountry trip leader for the Outdoor Recreation Committee, and a member of Kappa Alpha Theta. Most recently, Naomi worked as a kayak instructor at Trackers Earth, an outdoor education camp in Portland. Naomi is excited to join the AIF Clinton Fellowship and to immerse herself in the local community and culture through service.

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