Share on facebook. Share on twitter. Gorillas communicate in a number of ways, including through vocalizations! Vocalizations may be paired with a behavior. Prev Previous. Next Next. Related Posts. This gorilla sound is also known as Belch Vocalization or a contact call. The silverbacks of a band of gorillas usually start this sound. The rest of the band follow after. This sound is considered part of gorilla etiquette. Guides may imitate this call when out on gorilla treks for safety.
More reading: How to Choose a Gorilla Trek. This gorilla sound is described as a grunting sound, reminiscent of the sound a pig makes. A gorilla may make this sound when it wants to eat a particular plant, and another moves in to take it. This gorilla sound is made as an expression of playfulness and joy. It can also be made as an invitation to play. This sound is another sound of contentment, which can extend from the belch vocalization. Lastly, because chest beats can be heard over long-distances, we predict that both male size and the number of different males emitting chest beats are two important factors influencing group movement.
Recent work in Bwindi mountain gorillas speculated that one of the functions of chest beats is to mediate how groups use space, with smaller groups with fewer adult males likely avoiding larger ones with more males, which would help to explain their findings that larger groups having more exclusive home ranges and core areas than smaller groups We found no support for body size to influence the duration of chest beats, the number of beats, or the beat rate.
Acoustic signals are thought to be energetically expensive to produce 34 , 35 , 36 , 37 and we expected chest beats to be as well, with anecdotal accounts of gorillas that emit a high frequency of chest beats showing signs of exhaustion personal observation. This is in contrast to studies of savannah baboons Papio ursinus , showing that males with higher competitive ability produce longer vocalizations than weaker ones 48 , It is possible that the duration of chest beats and the beat rate decreases over time during periods of high chest beating frequency, and this decrease may be stronger in smaller males.
In general the relationship between body size and the duration of vocalizations and other acoustic sounds has been understudied in mammals 4 , In addition to conveying information on body size and other phenotypic traits , we would expect it to be important for chest beats to be individual-specific, thereby allowing receivers to discriminate the identity of the emitter.
Further study is needed to determine if there are individual signatures to the chest beats. Interestingly, we found smaller within-individual than between-individual coefficients of variation, particularly for chest beat duration and number of beats Notably, several temporal aspects of non-vocal drumming displays by chimpanzees Pan troglodytes , ruffed grouse Bonasa umbellus and great spotted woodpeckers Dendrocopos major show significant individual variation, similar to many vocalizations in a wide range of species 19 , 51 , For example, the buttress drumming of individual chimpanzees significantly differ in the mean duration and the mean number of beats 52 , The gorilla chest beat has both an acoustic and visual component, making it a multimodal signal.
Individuals in visual proximity can benefit from seeing and hearing the gorilla emitting the chest beat, whereas individuals further away rely on the acoustic component. Researchers have been interested in determining whether the different components of multimodal signals convey the same redundant signal or backup hypothesis or different information multiple messages hypotheses Gorillas live in tropical forests with dense vegetation, meaning that it is often difficult to see conspecifics even if they are close by.
Therefore, we argue that the evolution of the chest beat as a multimodal signal is at least in part to enhance signal transmission in an environment with limited visibility. We would expect the same messages to be transmitted in both visual and acoustic modalities, which would provide support for the redundant signal hypothesis.
However, these two hypotheses are not mutually exclusive, as the chest beat signal may transmit additional information, other than body size, which is then repeated in the visual and acoustic modalities, providing support for both hypotheses.
We conducted focal animal sampling periods of approximately 50 min duration to record all agonistic behaviour aggressive displays and any form of contact aggression , noting the identity of the male who initiated the interaction 31 , The focus here was on the aggressive displays involving a chest beat that were directed at conspecifics.
These data were then used to calculate a chest beat rate per male. We opportunistically collected sound recordings of silverback chest beats using a Sennheiser ME66 shotgun microphone and K6 power module with a MZW 66 windshield and a Zoom H4n recorder Zoom corp. Chest beats were recorded at a sampling frequency of 96 kHz and sampling accuracy was bit. Recording sensitivity was set at 80 for the duration of the study. Due to the logistically challenging nature of collecting sound recordings, we focused on six adult males from two social groups PAB and TIT between November and July We obtained a total of 36 chest beat sound recordings from six males Table 2.
In addition to the identity of the male that emitted the chest beat sender , we also recorded the distance using a distance meter; Leica Disto Ex, Leica Geosystems AG, Heerbrugg, Switzerland and the orientation of the sender with respect to the microphone to verify that these parameters did not influence peak frequency in any meaningful way.
We used the parallel laser method 56 to measure back breadth, defined as the maximum distance across the shoulders, including the rounded portion of the arms for details see Galbany et al. Measurements were obtained from an average of ten photos range 3—24 per individual, totaling photos of 25 males.
Acoustic analyses focused only on the non-vocal component of the gorilla chest beat display drumming vibrations emanating from the beating of the chest. Recordings were down-sampled for analysis to 48 kHz sampling frequency and bit sampling accuracy. Individual claps beats were identified as intensity spikes and marked in an annotation file Fig. Peak frequency was chosen as a single transparent measure to account for an observable frequency band of higher energy mainly between and Hz 21 see Supplementary Methods and Fig.
To test the hypothesis of a significant negative correlation between body size and peak frequency we fitted a linear mixed effects model with Gaussian error and identity link.
The response variable was the median peak frequency of each chest beat sequence i. The main predictor variable was back breadth. We included age as a control predictor and male identity as a random effect.
We then fitted three additional models examining the temporal characteristics of chest beats with the same structure with regard to the fixed effects, random effect and error structure as above but differing in the response variable.
The first of these tested the prediction that larger males have significantly longer chest beat sequences than smaller ones. The response variable was therefore the duration of the chest beat log-transformed. Next, we examined the prediction that larger males incorporated significantly more beats in their chest beats and have a faster beat rate than smaller males.
In both these models the response variable was the number of beats during each chest beat. In the later model we also accounted for the duration of the chest beat sequence by including it as a control predictor.
The analyses were conducted in R version 4. Continuous predictors were z-transformed to a mean of 0 and standard deviation of 1. We checked for normally distributed and homogenous residuals by visually inspecting qqplots and residuals plotted against fitted values. We examined model stability by re-fitting the models after excluding levels from male identity one at a time, and comparing the estimates derived from these models with the estimates from the original model.
No stability issues were found with regard to the main test predictor. The p-value for the main test predictor, body size, was computed using a likelihood ratio test comparing a full model with a reduced model not comprising this variable. Andersson, M. Sexual Selection Princeton University Press, Book Google Scholar.
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Apenheul Apenheul More than half of the primates roam freely among the visitors! Appearance Gorillas are the largest, strongest and heaviest of all primates. Habitat Western lowland gorillas live in the tropical rainforests of central Africa.
Lifestyle They live in groups of five to twenty individuals. Behaviour Gorillas are very quiet and friendly animals. Reproduction Female gorillas become fertile when they are about eight years old.
Situation in the wild Western lowland gorillas are threatened with extinction. Breeding programme Apenheul coordinates the EEP European breeding programme for western lowland gorillas. Fun facts Every evening, gorillas make a sleeping nest out of twigs and plants. They build their nest either in a tree or on the ground. Young gorillas sleep with their mother in her nest until they are about age three.
The silverback usually sleeps on the ground. Gorillas are renowned for the chest-beating sound they make.
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