Crocodilian Communication
A. mississippiensis threat call

When an alligator doesn't want to be disturbed, it may produce a "threat call" when approached. This is one of several kinds of threatening calls produced by a juvenile alligator. Both the spectrogram and the power spectrum of the call are shown below.


Alligator mississippiensis
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To listen to the call which is shown here, click on either 8-bit or 16-bit to download the sounds.


WHAT IT ALL MEANS

The spectrogram to your right shows the sound in a visual form - it plots frequency against time, with intensities shown as different colours. The power spectrum plots frequency against intensity, averaged over the whole call.


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DESCRIPTION QUALITY & SIZE DURATION RELATED CALLS
THREAT CALL
(high intensity hiss & bite)
8-bit
57.4 k
16-bit
229.4 k
2.66 s 1 | 2
Spectrogram

Power spectrum The spectrogram (above) shows a high level threat - a drawn-out hissing with an attempted bite at 1.0 s.

This call is an extension of a low level threat call (see "related calls" no.2, above). The threat which produced the low level hissing persisted and eventually the alligator escalated the threat to an actual attack (an attempt to bite). As before, the call is divided into two distinct sections. The first is associated with an expiration (breathing out) during which the animal produces the most intense hissing, and couples it with an attack. The second part (at 1.5 s) is a continued hiss during inspiration. This pattern may continue for several breaths, reverting back to a low level hissing if the attack is successful in deterring the threat. The only time that crocodiles makes a noise during inspiration is when they hiss like this. The sound is created by air passing through a constricted opening such as the glottis, nostrils or the even the palatal valve. In the call shown here, it is likely that contraction of the glottal valve is responsible. Like the low level threat, there are three prominent bandwidths, although a broad-bandwidth sound is created during the lunge - a very intense, sharp hiss. The power spectrum shows that the first of the prominent bandwidths contains the most energy over the entire call (at 1.16 kHz) - associated with the intense hiss during the lunge.

This is a "threat call" which, as the name implies, is used against potential threats or aggressors. This hiss variant is produced when the crocodile is starting to feel threatened in some way. Visual signals (e.g. opening the mouth, inflating the body, standing up) are also used in association with the hissing to reinforce the impact of the signal. In this signal, the threat was sufficient to cause the alligator to attack it with an attempted bite. After a single lunge, the alligator resumed hissing and posturing. Repeated lunges may occur if the threat does not disappear, or alternatively the animal may choose to flee (usually into water).

If you were to translate this call, it would mean "I warned you! Take this! Now go away or I'll bite you again."


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