Abstract
Ultrasonic vocalizations (USVs) constitute a substantial part of rodents’ communication repertoire. This article presents an overview of the current state of knowledge on USV in rodents, including its production, perception, and functions.

Table of Contents

Production of Ultrasonic Vocalizations

Rodents produce USVs through the rapid vibration of their vocal folds. The resulting sound waves are typically above the hearing range of humans (20 kHz), but within the auditory range of most rodents. The frequency, duration, and modulation of USVs vary depending on the species, context, and individual.

Perception of Ultrasonic Vocalizations

Rodents have specialized auditory structures that allow them to perceive and interpret USVs. The auditory cortex of rodents is organized into tonotopic maps, with different regions responding to specific frequency ranges. This organization enables rodents to discriminate between different types of USVs and to localize their source.

Functions of Ultrasonic Vocalizations

USVs serve various functions in rodent communication, including:

Communication in pups: Newborn rodents produce USVs to attract their mothers and solicit care.
Social interactions: Adult rodents use USVs to communicate aggression, fear, dominance, and submission.
Territorial defense: Some rodents emit USVs to deter intruders and defend their territories.
Mating: Male rodents produce USVs during courtship rituals to attract females.
Neuropharmacology: USVs can be modulated by various drugs, including alcohol and sedatives, providing insights into the neuropharmacological effects of these substances.

Table 1: Examples of Ultrasonic Vocalizations in Different Rodent Species

Species	Frequency Range (kHz)	Function
Mouse	20-100	Distress, aggression, mating
Rat	20-120	Communication in pups, social interactions
Hamster	20-150	Alarm calls, courtship
Guinea pig	20-60	Communication in pups, mating
Gerbil	20-100	Aggression, territorial defense

Conclusion

Ultrasonic vocalizations play a critical role in rodent communication. They provide a rich and complex means for rodents to express emotions, interact with conspecifics, and navigate their environment. Further research is needed to fully understand the intricacies of USV communication and its implications for rodent behavior and social organization.

Frequently Asked Questions (FAQs)

Q: Are ultrasonic vocalizations audible to humans?
A: Typically no, as they are above the range of human hearing.

Q: Why do rodents produce ultrasonic vocalizations?
A: To communicate with conspecifics in various contexts, such as attracting mates, defending territory, and expressing emotions.

Q: How do rodents perceive ultrasonic vocalizations?
A: Through specialized auditory structures in the brain that allow them to discriminate between different types of USVs.

Q: What are the different functions of ultrasonic vocalizations in rodents?
A: Communication in pups, social interactions, territorial defense, mating, and neuropharmacology.

Q: Can ultrasonic vocalizations be used to study rodent behavior?
A: Yes, by analyzing the frequency, duration, and modulation of USVs, researchers can gain insights into the emotional state, communication patterns, and social dynamics of rodents.

References

[1] Brudzynski, S. M. (2013). Ultrasonic vocalizations in rats. Current Opinion in Neurobiology, 23(1), 186-191. https://doi.org/10.1016/j.conb.2012.12.001
[2] Portfors, C. V. (2007). Types and functions of ultrasonic vocalizations in laboratory rats and mice. Journal of the American Association for Laboratory Animal Science, 46(1), 28-34.

Sense of Smell in Rodents

Rodents possess a highly developed sense of smell, which plays a crucial role in their survival and behavior. The olfactory bulb, located in the brain, receives sensory input from specialized olfactory receptor cells in the nasal cavity. These receptor cells bind to odor molecules, triggering electrical signals that are transmitted to the olfactory bulb for processing.

The olfactory system of rodents is highly sensitive, enabling them to detect a wide range of odors, including pheromones, food, and predators. Pheromones, chemical signals produced by other rodents, convey information about social status, reproductive status, and territorial boundaries. Rodents use their sense of smell to find food and avoid potential dangers, and they can discriminate between different odors based on their chemical composition.

In addition to its role in survival, the sense of smell also influences rodent behavior. Olfactory cues can trigger social and reproductive behaviors, such as mating and parenting, and can affect appetite, learning, and memory. Overall, the highly developed sense of smell in rodents is essential for their survival, behavior, and social interactions.

Research on

Ultrasonic vocalization in rodents, emitted at frequencies above the human hearing range, serves various communicative and emotional functions. Research in this field encompasses diverse aspects.

Social communication: Ultrasonic vocalizations play a crucial role in social interactions, including territorial defense, courtship, and maternal care. Different call types convey specific messages, allowing rodents to navigate social hierarchies and maintain group cohesion.
Emotional expression: Ultrasonic vocalizations reflect emotional states. Distress calls, emitted during pain or fear, alert conspecifics to danger. Anticipation calls, produced before a reward, indicate positive emotional experiences.
Neurobiology of ultrasonic vocalization: Studies investigate the neural mechanisms underlying ultrasonic vocalizations. Specific brain regions, such as the anterior cingulate cortex, are involved in call production and perception. The release of neurotransmitters, like dopamine, modulates call characteristics.
Clinical applications: Ultrasonic vocalization analysis has potential applications in disease diagnosis and treatment. Alterations in vocalizations can indicate specific neuropsychiatric disorders, such as autism spectrum disorder and schizophrenia. Research also explores using ultrasound as a therapeutic tool for reducing anxiety and other conditions.

Mouse Ultrasonic Vocalizations

Mice produce ultrasonic vocalizations (USVs) in the frequency range of 50-120 kHz. These vocalizations are used for communication, with different types of USVs indicating different social contexts. For example, territorial males produce aggressive USVs to warn others from their territory, while females produce courtship USVs to attract mates. USVs are also emitted during social interactions, such as grooming or playing, and during stressful situations, such as pain or fear. Mice can distinguish between different types of USVs, and they respond appropriately to them. For instance, male mice will retreat when they hear aggressive USVs, and females will approach when they hear courtship USVs. The study of mouse USVs has provided valuable insights into the social and communicative behavior of mice.

Rodent Vocal Communication

Rodents exhibit a diverse range of vocalizations to communicate various information. These calls serve various purposes, such as:

Territorial defense: Rodents use vocalizations to warn conspecifics of their presence and deter intruders from entering their territories.
Courtship and mating: Both male and female rodents utilize vocalizations to attract potential mates and establish dominance during courtship.
Parental care: Mothers use vocalizations to call their pups and guide them to safety or food sources.
Alarm and warning: Many rodent species emit specific calls when they sense danger, alerting others to potential threats.
Communication within groups: Rodents engage in vocal interactions within their social groups to maintain cohesion, exchange information, and resolve conflicts.

Mouse Scent Marking

Mice engage in scent marking behavior to communicate within their social groups and environments. They use three main types of scent glands: preputial, flank, and submandibular glands.

Preputial Glands:

Located in male mice, release pheromones that identify individuals and attract females.

Flank Glands:

Located on both male and female mice, release volatile compounds that mark territory and indicate social status.

Submandibular Glands:

Produce a unique scent that helps mice recognize each other within their colonies.

Mice use these scents to establish dominance, defend their territories, attract mates, and navigate their environments. They deposit scent marks on various surfaces, such as corners, objects, and other mice. The scents are detected by the vomeronasal organ in the nasal cavity, allowing mice to decode social information and modify their behavior accordingly.

Ultrasound and Rodent Behavior

Ultrasound technology has enabled researchers to study the vocal behavior of rodents, providing insights into social interactions and certain behavioral anomalies. Rodents produce ultrasonic vocalizations (USVs) at frequencies beyond the human hearing range, carrying valuable information about their emotional states, communication, and social dynamics. Ultrasonic equipment detects and records these vocalizations, revealing the rich acoustic complexities of rodent behavior.

Studies using ultrasound have uncovered the importance of USVs in communication. For example, pups emit distinct USVs to solicit maternal attention, and mothers respond by locating and retrieving their offspring. In social interactions, adult rodents produce USVs during aggressive encounters, courtship, and affiliative behaviors. These vocalizations convey information about the individual’s intentions, social status, and reproductive status.

Ultrasound has also been used to investigate behavioral changes in rodent models of neurodevelopmental disorders and psychiatric conditions. Abnormal USV production has been observed in animal models of autism spectrum disorder, schizophrenia, and depression, indicating potential links between these disorders and deficits in vocal communication. By analyzing ultrasonic vocalizations, researchers aim to gain a better understanding of the neurobiological underpinnings of behavior and develop novel therapeutic interventions.

Rodent Chemosensory Perception

Rodents possess a highly developed chemosensory system, enabling them to detect and respond to various chemical cues in their environment.

Olfaction: Rodents have a keen sense of smell, mediated by the olfactory epithelium. Sensory neurons within the nasal cavity detect odor molecules and transmit signals to the olfactory bulb, where they are processed and sent to various brain regions involved in odor recognition and behavioral responses.
Gustation: Rodents also have a well-developed sense of taste. Taste buds are located on the tongue and other oral surfaces, and they contain receptors that detect sweet, sour, salty, bitter, and umami (savory) tastes. These signals are transmitted to the brainstem for taste perception.
Trigeminal Chemoreception: The trigeminal nerve also plays a role in chemosensation in rodents. It innervates the nasal and oral cavities, and its sensory neurons can detect chemical irritants, such as pungent odors and capsaicin.
Specialized Chemoreceptors: Rodents possess specialized chemoreceptors that detect specific chemical cues. For instance, the vomeronasal organ, located at the base of the nostrils, responds to pheromones that convey social and sexual information.
Behavioral Implications: Rodent chemosensory perception has profound behavioral implications. Odors can trigger various behaviors, such as food seeking, avoidance of predators, and social interactions. Gustatory cues influence food preferences and consumption.