Meerkat close calling patterns are linked to sex, social category, season and wind, but not fecal glucocorticoid metabolite concentrations

Abstract

It is well established that animal vocalizations can encode information regarding a sender’s identity, sex, age, body size, social rank and group membership. However, the association between physiological parameters, particularly stress hormone levels, and vocal behavior is still not well understood. The cooperatively breeding African meerkats (Suricata suricatta) live in family groups with despotic social hierarchies. During foraging, individuals emit close calls that help maintain group cohesion. These contact calls are acoustically distinctive and variable in rate across individuals, yet, information on which factors influence close calling behavior is missing. The aim of this study was to identify proximate factors that influence variation in call rate and acoustic structure of meerkat close calls. Specifically, we investigated whether close calling behavior is associated with sex, age and rank, or stress hormone output (i.e., measured as fecal glucocorticoid metabolite (fGCM) concentrations) as individual traits of the caller, as well as with environmental conditions (weather) and reproductive seasonality. To disentangle the effects of these factors on vocal behavior, we analyzed sound recordings and assessed fGCM concentrations in 64 wild but habituated meerkats from 9 groups during the reproductive and non-reproductive seasons. Dominant females and one-year old males called at significantly higher rates compared to other social categories during the reproductive season. Additionally, dominant females produced close calls with the lowest mean fundamental frequencies (F0) and the longest mean pulse durations. Windy conditions were associated with significantly higher call rates during the non-reproductive season. Fecal GCM concentrations were unrelated to close calling behavior. Our findings suggest that meerkat close calling behavior conveys information regarding the sex and social category of the caller, but shows no association with fGCM concentrations. The change in call rate in response to variation in the social and ecological environments individuals experience indicates some degree of flexibility in vocal production.

Cost of dispersal in a social mammal: body mass loss and increased stress

“…We subsequently analysed faecal extracts for immunoreactive glucocorticoid metabolite concentrations using a group-specific enzyme immunoassay (EIA) for the measurement of 11b-hydroxyetiocholanolone [51]. The assay has previously been validated for assessing glucocorticoid output in captive meerkats [49] and has recently been applied successfully to study adrenocortical activity of wild meerkats [52]. Details on assay performance and characteristics, including full descriptions of the assay components and cross-reactivities, are provided elsewhere [51,53].…”

Evolution and neural representation of mammalian cooperative behavior

“…Because cooperation is so pervasive in nature, some scientists have posited that it represents the third pillar of evolution alongside mutation and natural selection (Nowak, 2012;Pennisi, 2009). In terms of a neo-Darwinian viewpoint, an individual acts cooperatively only if doing so will benefit its own fitness (in terms of survival and reproduction) (Hamilton, 1964a(Hamilton, , 1964bBourke, 2014), a hypothesis that is strongly supported by behaviors such as hunting (e.g., cheetahs cooperating to catch prey) (Pennisi, 2005;Boesch and Boesch, 1989), anti-predator behavior (e.g., slender-tailed meerkats cooperatively performing lookout, guarding and alerting the entire community when detecting dangers) (Clutton-Brock et al, 2001;Mausbach et al, 2017), and care for the young in many animals (Clutton-Brock, 2009). Compared with non-human animals, human cooperation can occur on a much larger scale and exhibit higher complexity.…”

Signalling adjustments to direct and indirect environmental effects on signal perception in meerkats

“…High vegetation density, for example, has a direct effect as it will increase sound attenuation and thus decrease the perception range [4][5][6][7]. The sound landscape, including sounds produced by other animals, wind or anthropogenic noise, can have similar direct effects by masking the vocal signal [8][9][10][11]. In contrast a reduction in food distribution can pose an indirect effect, as it can modify the distance between sender and receiver [12,13], forcing them to forage at greater distance, potentially out of their normal hearing range.…”

“…For example, during wet summer periods vegetation in dry savanna habitats is a lot denser and higher than during dry summer periods [24][25][26][27][28]. Background noise, such as wind [10,11] or the presence of noisy sympatric living species [29][30][31] and/or conspecifics [32], are further factors that can influence signal perception directly. Indirect effects on signal perception will mostly relate to the spacing among conspecifics.…”