The Alston’s brown mouse, known scientifically as Scotinomys teguina, is a small rodent known for its remarkable vocal abilities. Unlike most mice, this species produces intricate, song-like vocalizations, making it a subject of scientific interest. These complex sounds distinguish it within the rodent family.
Anatomy of the Song
The vocalizations of Scotinomys teguina are primarily ultrasonic, meaning their high frequencies are beyond the range of human hearing without specialized equipment. The song is structured as a rapid series of discrete notes, often described as a “trill” or “chirp.” It spans a frequency range of 22 to 43 kilohertz, with a dominant frequency of 22 to 26 kilohertz. Chirps occur up to 20 times per second.
Producing such rapid and high-pitched sounds requires specific anatomical adaptations within the larynx. Singing mice generate their songs using an intralaryngeal whistle mechanism, where a glottal air jet impinges on an internal structure called the alar cartilage. The inflation of a hypertrophied ventral pouch, a specialized sac within the larynx, is also involved in sound production. The frequency of the song is determined by the speed of this air jet, which can be precisely modulated by changes in airflow and the size of the glottal opening. Muscles such as the cricothyroid and thyroarytenoid play a role in controlling these fine adjustments.
Communication and Social Behavior
The songs of Scotinomys teguina serve various social functions. Males use their songs to attract mates. They also defend territories from rival males. The presence of a female can influence a male’s singing, leading to changes in the song’s structure or tempo.
When two males encounter each other, they may engage in competitive “sing-offs” or vocal duels. These precise, timed exchanges allow individuals to assess a rival’s strength without physical confrontation. Such vocal displays help the mice avoid injury and conserve energy.
A Model for Vocal Communication Research
The Scotinomys teguina has emerged as an animal model for neuroscientists studying the brain’s control over vocal communication. Its ability to produce complex, precisely timed songs, similar to human speech and bird song, offers unique insights into neural circuits. Researchers investigate how the brain coordinates the timing and precision of these vocalizations, examining the interplay of various muscle groups like the cricothyroid and digastricus, which control frequency modulation and jaw opening.
Studies using techniques like viral tract-tracing have identified specific brain regions involved in the singing mouse’s vocal circuitry. These include the gigantocellular reticular formation, which acts as a central pattern generator, and midbrain areas such as the ventrolateral periaqueductal gray and parabrachial nucleus. Forebrain regions associated with social cognition and energy balance, including parts of the hypothalamus, amygdala, and motor cortex, also show activity during vocalization. Research into the FOXP2 gene, linked to speech disorders in humans, further connects this animal model to understanding conditions like stuttering or speech control issues in neurological diseases such as Parkinson’s.
Habitat and Physical Traits
Alston’s singing mouse inhabits the high-altitude cloud forests of Central America, ranging from southern Mexico to western Panama. These mice are typically found at elevations between 1,100 and 2,950 meters, preferring wet habitats with subtropical climates. They are often observed in grassy clearings and along the edges of forests.
Physically, Scotinomys teguina is a small rodent, usually weighing between 10 and 15 grams. It has a dark brown coat, with its underparts varying from dark gray-brown to orange-brown. The tail is blackish and lightly haired, and its feet are black. These mice are predominantly insectivorous, with their diet consisting mainly of beetles and other small insects, supplemented by a small amount of seeds and fruits. In the wild, they are active during twilight hours, though laboratory studies indicate they are most active during the morning.