Caller ID in Goitred Gazelles

As their name implies, male goitred gazelles (Gazella subgutturosa) have a lump, resembling the human Adam’s apple, at the front of their necks. Females of the species have a smaller lump, reflecting their smaller larynx. Goitred gazelles are relatively vocal; they produce both oral and nasal calls. Males emit calls during the rutting season to advertise their virility to potential mates. In contrast, females are most vocal during the nursing period in spring. In the first few weeks of life, young goitred gazelles stay hidden when not nursing. Later, as juveniles begin grazing they vocalize to stay in contact with their mothers.

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Figure 1. A goitred gazelle (Gazella subgutturosa). (From Flickr/justchaos)

Researchers at the Ecocenter “Djeiran in
Uzbeckistan (Volodin et al. 2011) decided to see if juvenile calls encoded information about the sex and identity of the caller. Such information would be valuable to mothers attempting to relocate their young.

Twenty goitred gazelles less than ten days old were removed from a captive population and housed in enclosures. Over the next five weeks, calls were recorded from the juveniles and matched to video images to determine the call type (oral or nasal). A random selection of 25 oral and 25 nasal calls from each individual were analyzed with bioacoustics software (Figure 2).

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Figure 2. Left: a waveform (a), and spectrogram (b and c) recording of an oral (left) and nasal (right) call from a juvenile goitred gazelle. The darker horizontal bands in the spectrograms represent different formants. Right: an image of a juvenile goitred gazelle showing the length of the oral track. (From Volodin et al., 2011)

Male and female calls were significantly different with respect to differences in
formants (one or more frequency ranges within a sound, that impart a special quality or timbre; see Figure 2). In males, for example, the formants were lower than those produced by females regardless of call type. Thus, the caller’s sex is identifiable to others in the herd.

The individual identity of the caller was encoded in a combination of acoustic variables, including formants, fundamental frequency, and power variables. Furthermore, oral calls were better able to encode identity than nasal calls. Not surprisingly, roughly 50% of juvenile calls are oral calls during the first four weeks of life.

As juvenile goitred gazelles leave their natal territories and begin to graze over large areas they join other mother-offspring units. Individually recognizable calls may help reunite mothers with wayward offspring.


References

Volodin, I., Lapshina, E., Volodina, E., Frey, R., & Soldatova, N. (2011). Nasal and Oral Calls in Juvenile Goitred Gazelles (Gazella subgutturosa) and their Potential to Encode Sex and Identity Ethology, 117 (4), 294-308 DOI: 10.1111/j.1439-0310.2011.01874.x