The Role of Grunt Calls in the Social Dominance Hierarchy of the White-Lipped Peccary (Mammalia, Tayassuidae)

Production of multimodal signals to assert social dominance in white-lipped peccary (Tayassu pecari)

In this study we aimed to examine whether the 'redundancy' (a backup function to ensure the signal transmission) or 'multiple messages' (sensory communication system in combination) hypothesis would explain the function of multimodal communication of white-lipped peccaries (Tayassu pecari-WLPs). We also aimed to assess the individual factors (the social rank and sex of the sender) influencing the production of, and responses to unimodal and multimodal signals. We determined the social rank of 21 WLPs living in two captive groups and quantified the production of unimodal and multimodal signals when displaying threatening and submissive behaviors. WLPs most often produce multimodal signals independent of a previous unimodal signal failure, which suggests that they were adding more information, such as the sender's size, rather than merely increasing efficacy by engaging a different receiver's sensory channel. There was no effect of the sender's sex in the production of, and responses to, multimodal signals. However, the higher the sender's social rank, the greater the production of multimodal signals when WLPs were displaying threatening behaviors; whereas the lower the sender's social rank, the greater the production of multimodal signals when displaying submission behaviors. Multimodal signals elicited more non-aggressive responses than did the unimodal signals when displaying a threat. Moreover, the higher the sender's social rank, the greater the occurrence of non-aggressive responses to multimodal signals when displaying a threat; whereas the opposite occurred when displaying submission. Our findings support the 'multiple messages' hypothesis to explain the function of multimodal signaling during agonistic interactions in WLPs. Additionally, both the production of, and responses to, multimodal signals are related to the sender's social rank. These results allow us to suggest that the production of multimodal signals may have a key role in mitigating conflict and thus promoting group cohesion among white-lipped peccaries.

Multidimensional nature of dominant behavior: Insights from behavioral neuroscience

Social interactions for many species of animals are critical for survival, wellbeing, and reproduction. Optimal navigation of a social system increases chances for survival and reproduction, therefore there is strong incentive to fit into social structures. Social animals rely heavily on dominant-submissive behaviors in establishment of stable social hierarchies. There is a link between extreme manifestation of dominance/submissiveness and behavioral deviations. To understand neural substrates affiliated with a specific hierarchical rank, there is a real need for reliable animal behavioral models. Different paradigms have been consolidated over time to study the neurobiology of social rank behavior in a standardized manner using rodent models to unravel the neural pathways and substrates involved in normal and abnormal intraspecific social interactions. This review summarizes and discusses the commonly used behavioral tests and new directions for the assessment of dominance in rodents. We discuss the hierarchy inheritable nature and other critical issues regarding hierarchical rank manifestation which may help in designing social-rank-related studies that serve as promising pre-clinical tools in behavioral psychiatry.

Third-party conflict interventions are kin biased in captive white-lipped peccaries (Mammalia, Tayassuidae)

Third-party interventions may regulate conflicts to reduce aggression and promote cohesion amongst group members, but are rarely documented in ungulates. The white-lipped peccary (Tayassu pecari) lives in mixed-sex herds of hundreds of individuals in Neotropical forests, which are likely to benefit from mechanisms that sustain social cohesiveness. We examined third-party conflict interventions between individuals in captive groups of white-lipped peccaries. During a period of 60 days, we recorded agonistic interactions and occurrences of third-party conflict interventions, and estimated the genetic relatedness between the individuals involved using multilocus microsatellite genotypes. Most third-party conflict interventions were by the dominant male of each group, resulting in conflict termination 100% of the time. Our results also revealed that white-lipped peccaries favour their closest relatives and that individuals showed lower levels of aggression towards kin than to non-kin, and interventions on behalf of kin were more frequent than on behalf of non-kin. Our findings support the idea that genetic relatedness is fundamental in both social structure and third-party conflict interventions in this species, allowing us to suggest that kin selection could have a key role in the evolution of social behaviour of white-lipped peccaries.

Territorial calls of the bat Hipposideros armiger may encode multiple types of information: body mass, dominance rank and individual identity

In highly vocal species, territorial aggression is often accompanied using vocalizations. These vocalizations can play a critical role in determining the outcome of male-male agonistic interactions. For this, vocalizations of contestants must contain information that is indicative of each competitor's fighting ability as well as its identity, and also contestants must be able to perceive information about the physical attributes, quality and identity of the vocalizer. Here, we used adult male Great Himalayan leaf-nosed bats (Hipposideros armiger) to test whether territorial calls encoded honest information about a caller's physical attributes, quality and individual identity. We did this by exploring the relationships between territorial calls and two potential indices of fighting ability: body mass and dominance rank. Using synchronized audio-video recording, we monitored bat territorial calls and dominance rank of 16 adult male H. armiger in the laboratory. Additionally, habituation-dishabituation playback experiments were performed to test for vocal discrimination. Results showed that body mass was negatively related to minimum frequency and positively related to syllable duration. Dominance score was also negatively related to minimum frequency and positively related to peak frequency. Furthermore, a discriminant function analysis suggested that territorial calls encode an individual signature. Therefore, our data show that males have the ability to utilize this vocal individual signature to discriminate between vocalizing males. In short, territorial calls of male H. armiger contain information about body mass, dominance rank and individual identity, and contestants are probably capable of perceiving this information and may use it to make appropriate decisions during agonistic interactions.

Use of the ACP® and BTS extenders for cooling at 15°C white-lipped peccary (Tayassu pecari) semen

ABSTRACT: Knowledge about reproduction of white-lipped peccary is of great importance to assist with the conservation of this species and enable its rational use in captivity. This study aimed to evaluate the effect of ACP-103®, ACP-116® and BTS semen extenders on sperm viability during cooling of Tayassu pecari semen. Five ejaculates from four adult males were chilled. The animals were submitted to the protocols of sedation and anesthesia for semen collection by the electroejaculation method. After collection, the semen was macro- and microscopically assessed and diluted to reach 35x106 spermatozoa/mL in each of the three different extenders tested. The fresh-extended semen was packed in a BotuFLEX® thermal box to keep samples at 15°C for 24 hours. After cooling, the following semen parameters were analyzed: sperm motility, functional and structural integrity of sperm membranes, mitochondrial activity, chromatin condensation, and the thermoresistance test was performed. The parameters sperm motility, structural and functional integrity of sperm membranes, mitochondrial activity, and chromatin condensation were preserved after use of the extenders tested, and were similar to those of in natura semen (p>0.05). Curvilinear velocity (VCL) (p<0.05) was the only parameter with reduced values after cooling regardless of the extender used. The percentage of sperm with normal morphology was greater in samples cooled using the BTS extender (p<0.05). The ACP-103®, ACP-116® and BTS extenders can be used for the cooling and preservation of white-lipped peccary semen at 15°C for 24 hours.