Elsevier

Animal Behaviour

Volume 78, Issue 3, September 2009, Pages 741-746
Animal Behaviour

Noise-dependent vocal plasticity in domestic fowl

https://doi.org/10.1016/j.anbehav.2009.07.004Get rights and content

Since acoustic communication is considerably constrained by environmental noise, some animals have evolved adaptations to counteract its masking effects. Humans and New World monkeys increase the duration of brief vocalizations (below a few hundred milliseconds) as the background noise level rises, a behaviour that increases the detection probability of signals in noise by temporal summation. We found that domestic fowl, Gallus gallus domesticus, exhibited the Lombard effect, that is, a regulation of vocal amplitude depending on the background noise level. This vocal mechanism for communication in noise is also found in mammals and other bird species. However, in contrast to primates, the chickens did not regulate the duration of their brief call syllables. This evidence for a lack of regulation of syllable duration may hint at limitations in the degrees of freedom for signal coding. Overall, our findings indicate that the common problem of acoustic communication in noise has led to the evolution of a common solution, the Lombard effect, but also to special adaptations in different taxa.

Section snippets

Animals and Housing

The experiment was conducted at the Institute of Animal Welfare and Animal Husbandry in Celle, Germany. As subjects we used 21 broiler chickens of the strain Ross 308 at an age of 4 weeks. All subjects were reared and kept together in a group of 60 individually marked animals in a litter floor system (3.9 × 3.7 m and 2.6 m high) with straw. In this chicken compartment the birds were maintained on a 12:12 h light:dark schedule, with air temperature ranging between 21 and 23°C (but the local

Results

Subjects significantly increased the sound pressure of their calls in response to an increase in the background noise level (within-subjects effect: F4,72 = 21.5, P < 0.01; linear within-subject contrast: F1,18 = 34.7, P < 0.001; Fig. 3a). On average ±SE, the chickens called at 61 ± 2 dB in ambient noise and at 76 ± 1 dB in maximum background noise.

Call duration, however, was not regulated according to the background noise level, but rather remained stable at values around 150 ms (within-subjects effect: F4,72

Discussion

We investigated noise-induced modulations in chicken calls and found that the birds exhibited the Lombard effect, that is, an increase in vocal amplitude in response to an increase in the background noise level. This finding is in line with earlier studies that showed the Lombard effect in songbirds (Cynx et al., 1998, Brumm and Todt, 2002, Kobayashi and Okanoya, 2003) and also nonsongbirds (Potash, 1972, Manabe et al., 1998). Our findings support the view that the Lombard effect is a general

Acknowledgments

We thank Erwin Nemeth for his help with the data preparation. He and Rachel Page, as well as Valentin Amrhein and two anonymous reviewers, gave helpful comments on the manuscript. Financial support was provided by the German Research Foundation (Emmy Noether fellowship to H.B., award BR 2309/6-1).

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    L. Schrader is at the Friedrich-Loeffler-Institut, Institute of Animal Welfare and Animal Husbandry, Dörnbergstr. 25/27, 29223 Celle, Germany.

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