Sound the Alarm: Traffic noise increases predation threat to prairie dog colonies

April 7, 2020April 7, 2020 Brandi Pessman 0 Comments alarm calls, cities, prairie dogs, predation threat, traffic noise

Featured Image Caption: Traffic noise may challenge the ability of prairie dogs to detect predators and warn other prairie dogs. (Joe Ravi via Wikimedia Commons)

Reference: Shannon, G., McKenna, M. F., Wilson Henjum, G. E., Angeloni, L. M., Crooks, K. R., & Wittemyer, G. (2019). Vocal characteristics of prairie dog alarm calls across an urban noise gradient. Behavioral Ecology, 31(2), 393-400. https://doi.org/10.1093/beheco/arz200

Reference: Shannon, G., Crooks, K. R., Wittemyer, G., Fristrup, K. M., & Angeloni, L. M. (2016). Road noise causes earlier predator detection and flight response in a free-ranging mammal. Behavioral Ecology, 27(5), 1370-1375. https://doi.org/10.1093/beheco/arw058

Humans are Noisy

How many times have you driven to a new place and, when you got close, needed to turn down the radio so you could focus? The extra noise that the music makes can be really distracting when you need to be alert and looking for something. Drivers have the ability to reduce the noise by turning down their radio volume, but animals aren’t always so lucky when there is a lot of noise in their environment.

Prairie dogs produce alarm calls – series of high-pitched barks – that warn the predator and other prairies dogs that the predator has been detected. (*John via Creative Commons*)

Humans are making profound and rapid changes to the environment, forcing many animals to be flexible in their behaviors. One big way we affect the lives of animals is through all of the noise we make, especially with city traffic. This noise could impact the ability of animals to attract mates, secure food, or avoid predation.

Many animals require alertness and focus to identify, locate, and warn others of lurking predators. Prairie dogs are no exception – they produce alarm calls, which are series of brief, high-pitch barks, that are used to communicate to other prairie dogs that a predator is close and to warn the predator that they have been spotted. Noise produced by humans could present challenges for prairie dogs to locate predators and for other prairie dogs to be able to receive the message that a predator is near. Prairie dog populations have been rapidly declining (by 95%) due to urbanization and pest management practices, and the increased threat of predation could push their numbers even lower.

Sound the Prairie Dog Alarm

Prairie dogs are highly social animals that live in colonies, or towns, that consist of multiple family groups. As I am sure you would do anything to protect your family, prairie dogs use alarm calls to make sure their family is safe from predators, such as snakes, hawks, coyotes, and badgers.

Prairie dogs are highly social animals that form colonies that consist of many families. (*via Piqsels*)

In Fort Collins, Colorado, prairie dog colonies are located in areas that differ in the amount of traffic noise present. Researchers at Colorado State University conducted two studies to determine if traffic noise affects vigilance, flight response, and the alarm calls of prairie dogs. In a 2016 study, the researchers used recorded noise to investigate how vigilance and flight response of prairie dogs differs between no noise and some noise. In a more recent study, scientists investigated the frequency (Hz) of alarm calls at three sites that had high, medium, or low levels of traffic noise.

Human observers used themselves as predatory cues to encourage prairie dogs to sound their alarm calls. When noise was present, researchers found that prairie dogs became alert and fled when humans were at a greater distance than when there was no noise. On the other hand, scientists predicted that increasing amounts of low-frequency noise would result in prairie dogs raising the frequency of the alarm calls to be heard over the noise, but there was no strong evidence that this was the case in any of the three sites. Perhaps the frequency of noise does not significantly overlap with the frequency of alarm calls.

Fret the Threat

Prairie dog colonies can be found in and near cities where there are varying amounts of traffic noise. (*Ron Singer via Wikimedia Commons*)

When traffic noise is present, predators can more easily sneak up on unsuspecting prairie dogs. As a result, prairie dogs have adjusted their behavior by increasing vigilance and flight response so that predation can be avoided sooner. However, the prairie dogs aren’t changing the characteristics of their alarm calls. These results suggest that prairie dogs consider traffic noise as an increased threat to predation, rather than a mask to their alarm calls.

Prairie dogs, like other animals that have taken up habitats in cities, have the ability to adjust their anti-predator behaviors when noise is present. This flexibility will become increasingly important as humans continue to alter the habitats and lives of animals living in and near cities around the world. There are many ways that you can help out and reduce traffic noise in cities, such as taking public transportation and riding your bike.

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