Biology Reference
In-Depth Information
Fig. 6.4
Amplitude and frequency of the great tit (
Parus major
) call in a quiet area (
no noise
) and
in a noisy area in which frequencies (
frequency shift
) or amplitude (
amplitude shift
) can be
modified (Reproduced with permission from Katti and Warren
2004
)
It seems a bit strange that this effect has been proved in animals 60 years later.
One of the first researchers to investigate this effect on animals was Potash (
1972
),
observing that the Japanese quail (
Coturnux coturnix japonica
) changes the ampli-
tude of their vocalizations when experiencing a loud white noise.
Today several investigations have confirmed the Lombard effect, especially in
urban areas, and some species such as the nightingale (
Luscinia megarhynchos
) are
able to change the amplitude of their sound from working days as compared with
weekend days (see Brumm and Todt
2003
).
Also, frogs are able to change their amplitude when the background noise
increases. In insects this phenomenon seems not be present. In fact, the stridulating
mechanisms of an insect cannot be modulated.
Wind becomes noise when masking some biological signals, as studied by
McNett et al. (
2010
) on the effects of wind-induced noise on the reproductive
behavior of the treehopper
Enchenopoda binotata
('ptelea').
This species utilizes plant-borne vibrations to communicate: the male and the
female produce a duet before mating. These authors have observed that the male
uses a relatively wind-free period to communicate. Females were observed to
respond to male vibration in less measure in the presence of wind-borne vibrations
In the marine environment, Holt et al. (
2008
) have found that killer whales or
orcas (
Orcinus orca
) increase their call source level by 1 dB for every 1-dB increase
in background noise level (Fig.
6.5
).
Laboratory experiments on hand-reared individuals of great tit (
Parus major
)
(Langemann et al.
1998
) have demonstrated that in this species in a noisy environ-
ment sensitivity was only in function of the noise level and not dependent on
Search WWH ::
Custom Search