The Better to Hear You With? Noise Mitigation in Captive Environments

By Victoria Garduno

African Cheetahs are facing one of the most dire extinction crises in the world today. Zoos and sanctuaries around the globe have been working tirelessly to try and protect them, first by navigating them through arguably one of the worst genetic bottlenecks we have seen to date, and now by carefully walking the tightrope that is captive cheetah breeding. Suffice to say, captive cheetahs are delicate creatures [1]. So you can imagine my surprise when, on a recent trip to Busch Gardens Tampa, I discovered that they had built a brand new roller coaster attraction…..which passed less than 100 yards from their cheetah enclosure.

Busch Gardens2

Portion of Busch Gardens Park Map, with cheetah enclosure in blue, and coaster passby in red.

 

The average roller coaster produces sound at anywhere from 40 to 90 decibels as it passes by an observer. This is about as loud as a jackhammer, and just shy of the point where hearing loss occurs in humans. In fact, the most noise is measured from the side of the cars, rather than the front or back[2], which means that the position from which the cheetahs, or any other animal which may be exposed, experiences the noise is actually the most extreme position, acoustically speaking. However, noise in captive situations is not limited to places which employ ride attractions. Many popular zoos have music and performance attractions, which, with the use of microphones, speakers, and amplifiers, are more than capable of producing enough sound to affect the captive environment. In some cases, the noise output from concerts or performances may even exceed the level produced by ride attractions.[3] Research has shown that zoo animals can be affected even by the crowds that visit them, showing increased vigilance and movements in response to escalating crowd noises.[4]

Chart showing relative decibel levels of common sounds.

Chart showing relative decibel levels of common sounds.

So then, what may be done in terms of noise mitigation? Continuing with my Busch Gardens case study, I secured an audience with a senior cheetah keeper at the park, who was able to shed some light on what had been done in this particular situation to reduce the effect of the coaster noise on the cheetahs. Surprisingly, most of the measures employed were behavioral. The most important part, she said, was done even before the cheetahs arrived in Tampa, when they were still at the sanctuary where they were received from, in Africa. Recordings of the cars going by on the track were made, and sent over to the sanctuary, where they were played for the cheetahs who were slated to take up residence at the park. This effectively habituated them to the type and level of the noise that they would experience, and decreased any negative effects which could be caused by sudden or unexpected exposure. Additionally, the recordings could be played softly at first, and then increased in volume to real-life levels once the cheetahs were comfortable. In other cases, habituation has been shown to reduce stress and startle responses in animals, both captive and wild, however, stress levels may remain elevated [5].

cheetah rest

In terms of sound design, clever engineering may be employed to reduce noise levels and reduce stress on captive animals. In the case of the roller coaster, there are many techniques which reduce noise, including filling the track with sand or vermiculite, and the addition of walls, buildings, or tunnels to absorb sound. These approaches may reduce the sound produced by ride attractions by as much as 20 decibels [6]. Additionally, animal enclosures also play a role in dampening sound. The shape of an enclosure has been shown to affect the type and level of sound that reaches the occupants, as well as the addition of trees, water features, rocks, and ‘ambient’ or ‘natural’ sounds. Exhibits which feature plexiglass fronts are also extremely effective against crowd noises, as those tend to be directionally oriented at the front area of an exhibit.[7]

sound2

In the case of the Busch Gardens cheetah coalition, this story does have a happy ending. Until recently, no cheetah participating in an animal ambassador program had ever had a successful litter. That changed in November of 2014, when one of Busch Gardens’ ambassador cheetahs, who had been previously housed at the park, produced a healthy litter of four cubs, two of which remain at the park. It would appear that the sound mitigation techniques, both behavioral and structural, were successful in reducing stress sufficiently for the cheetahs to feel comfortable enough to breed. If these methods are successful in cheetahs, it is probably safe to assume that they will also be successful in other, less fragile species. If we can implement these measures in zoos and sanctuaries across the globe, we may be able to improve the welfare of captive animals everywhere, and maybe even save ourselves a headache or two as well.

New arrivals!

New arrivals!

[1] O’Brien, S., M. Roelke, L. Marker, A. Newman, C. Winkler, D. Meltzer, L. Colly, J. Evermann, M. Bush, and D. Wildt. “Genetic Basis For Species Vulnerability In The Cheetah.” Science: 1428-434. Print.

[2] Menge, Christopher W. “Noise from Amusement Park Attractions: Sound Level Data and Abatement Strategies.” Noise Control Engineering Journal: 166. Print.

[3] “Sound Advice Note 10.” – Rock and Pop. Ed. David Adams. 1 Jan. 2007. Web. 26 Mar. 2015.

[4] “Zoo Visitor Effect on Mammals: Does Noise Matter?” Applied Animal Behavior Science 156 (2014): 78-84. Print.

[5] Knight, Richard L. “Responses of Wildlife to Noise.” Wildlife and Recreationists Coexistence through Management and Research. Washington, D.C.: Island, 1995. Print.

[6] Davis, Joshua I., Charles Birdsong, and Harold Cota. “Vibroacoustic Study of Circular Cylindrical Tubes in Roller Coaster Rails.” Noise Control Engineering Journal: 333. Print.

[7] AZA Ape TAG 2010. Chimpanzee (Pan troglodytes) Care Manual. Association of Zoos and Aquariums, Silver Spring, MD. 1.4 “Sound and Vibration”

 

14 thoughts on “The Better to Hear You With? Noise Mitigation in Captive Environments

  1. Amy D'Arcey

    I’m glad that they are taking that level of care with the cheetahs to habituate them to the noise but I have to admit the whole situation sounds ridiculous! I imagine that was your first reaction seeing the enclosure right next to the roller-coaster. This was really the only way they could design things? Even if the animals are used to the noise (and they must be if they are breeding successfully) it must be nerve-wracking to have to hear it all day.

  2. mberne

    I think that it is a good idea to habituate the cheetahs to noises, but more normal noised that would be seen in the wild may be a better idea. I know i would never want to ‘live’ nest to a roller coaster all day! I have looked into Busch Gardens cheetah program and they use dogs as companions for the cheetahs to feel more comfortable and less skittish. I wonder if these are the same cheetahs that have animal companions that allow them to breed successfully!

    1. vgarduno

      I did ask about the use of dogs with the cheetahs, and the keeper said that dogs are mostly used for male cheetahs, to mimic the sort of ‘brother’ relationships that wild cheetahs have during adolescence, and that they naturally grow apart as the cheetah ages, so they don’t usually stay together past adulthood. So the use of the dogs was not a factor in their responses to the noise levels.

  3. Gabe

    I really like your discussion of the effects of noise on animal. I have studied this a lot in my program, working with Animal Shelters who are very concerned about the effects of noise on their animals. Surprisingly, the noise of the roller coaster was somewhat quieter than the recorded volumes in some shelters. The chronic stress these noise levels produces is detrimental to the mental and physical health of the animals in the shelter. If we could apply the same lessons to cheetahs, we could start breeding them for reintroduction, not just show.

  4. Lisa Angeloni

    Interesting blog — I’m actually surprised that they thought about habituating the cheetahs to roller coaster noise prior to putting them in the enclosure. I like the suggested ideas for reducing noise levels experienced by zoo animals with enclosure design. It would be interesting to record noise levels in enclosures across zoos to look at variation across types of enclosures and to rate zoos from an acoustic perspective.

  5. sberg

    I really liked this article about the cheetahs. I can’t believe they put a roller coaster next to the cheetahs or the other way around, they really could have placed each other differently. However it is a good idea to let the, start getting used to loud, soft, and medium noises just for the fact that there is human population growing each day too.

  6. ematth

    It is great to hear that they are addressing sound disturbance at places like Busch Gardens. I had never thought about how sound would impact captive animals, but how could it not? Many zoos are located in the center of cities as well in order to attract tourists and encourage funding and attention to the zoo. This could be really harmful to any captive animals without the implementations that you have suggested, such as sound dampeners and plexiglass.

  7. reneev

    I never though about the roller coaster noise affecting animals at places like Busch Gardens. I think it’s definitely an issue because some animals have very sensitive hearing and shouldn’t be exposed to those levels of noise. I think it’s great that they are thinking of new and innovative ways to create noise barriers so the animals can have a better quality of life.

  8. amajor

    Oh, wow, this is just grand. Simply grand. You’ve covered a problem that has been over-looked or ignored by developers or even keepers and you pointed out an example of how working on this sort of ordeal has improved the welfare of an animal’s life immensely. I would have to say that this is a grand step to the right direction in regards of career means (if doing stuff like this is what you want to work towards). Again, you did a grand job or as Theodore Roosevelt would say, “Bully for you!!!!”

  9. mplatt

    I find it very inspiring that you went so far as to talk to the Cheetahs’ keeper! I wish there were more ways to diminish the noise instead of just having the cheetahs habituate to it. Like we learned in class habituation does not mean they are not stressed it just means they are used to it. The fact that they bred was a good indication that the measures they took were successful in limiting the stress which is really amazing! Great post!

  10. ssteele1

    This is really cool! I was preparing for another un-settling story. Another great example of how animal behavior can be used to mitigate, and improve, captive situations! I wasn’t convinced that the Habituation would completely fix the problem, but the successful litter made it pretty convincing, since Cheetahs are challenging to breed. Great topic!

  11. leorah

    I haven’t heard this angle taken before on the detriments of sound or sound pollution. Fascinating. I think that the topic addressed here is more welfare than conservation, but I think this has really cool implications across the field of animal behavior, including captivity and breeding. Very unique topic, and a really interesting read. Thanks!!

  12. Savimay

    I think it’s great that sound reduction lowered the stress levels in cheetahs. I’m sure this would be the case for several other species as well. Like Dr. McKenna was talking about how much sound influenced marine mammals. People don’t often think about the impacts sound would have on animal behavior. I agree with Leorah that mitigating sound would have greater implication on animal welfare than conservation but it is still an issue that we should consider in the future, especially for marine mammals and animals more sensitive to sounds.

  13. Lacey Humphreys

    I really like how the people at Busch Gardens did their research before bringing the cheetahs into their facility. It seems as if they really know what they are doing. I never thought about how noise can affect felines in captivity. How well are they habituated to the noise though? In my experience with my two cats at home, it doesn’t matter how many times a week I vacuum, every time it comes on their ears go back and they scurry away as fast as possible. They never habituate to it.

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