Why does a rat scream at another rat? - briefly
Rats produce loud ultrasonic cries when they perceive a threat or experience intense stress, using the sound to warn or intimidate nearby individuals. The vocalization functions as an alarm signal that can trigger avoidance or defensive behavior in other rats.
Why does a rat scream at another rat? - in detail
Rats produce a loud, high‑frequency vocalization when confronted by another rat in several specific situations. The sound, often audible to humans, differs from the ultrasonic calls used in routine communication and signals heightened arousal or distress.
The primary triggers are:
- Territorial intrusion – an unfamiliar rat enters a resident’s enclosure, prompting a defensive scream that warns the intruder and mobilizes the resident’s attack response.
- Social dominance contests – during fights for hierarchy, the dominant individual emits a sharp cry that accompanies biting and lunging, reinforcing its status.
- Maternal protection – a mother rat emits a piercing call when a pup is threatened or separated, alerting nearby adults and deterring predators.
- Pain or injury – physical harm, such as a bite wound, elicits an immediate high‑pitch scream that serves as an alarm to conspecifics.
- Predator detection – exposure to a predator cue (e.g., cat odor) can cause a rat to emit a distress scream that alerts others to danger.
Physiologically, the scream originates from rapid vibration of the laryngeal muscles, driven by a surge of adrenaline and cortisol. This activation expands the vocal folds, producing a sound with a fundamental frequency of 2–5 kHz, well within human hearing range. The acoustic pattern includes a steep onset, a brief plateau, and a rapid decay, which laboratory recordings show correlates with elevated heart rate and blood pressure.
Neurobiologically, the amygdala and hypothalamic–pituitary–adrenal (HPA) axis coordinate the response. Sensory input about the rival or threat reaches the amygdala, which triggers the HPA axis to release stress hormones. Simultaneously, the periaqueductal gray (PAG) in the midbrain orchestrates the motor pattern for the vocal output. Lesion studies demonstrate that disabling the PAG eliminates the scream without affecting other vocalizations, confirming its central role.
Behavioral experiments reveal that the scream functions as a public signal:
- Deterrence – conspecifics receiving the call reduce their approach, decreasing the likelihood of escalation.
- Recruitment – nearby rats may converge on the source, providing assistance in defensive encounters or facilitating collective mobbing of predators.
- Information transfer – the acoustic structure encodes the caller’s emotional state; higher amplitude and longer duration indicate greater intensity of threat.
In summary, the audible scream emitted by a rat toward another rat is a multifaceted alarm signal triggered by territorial challenges, dominance disputes, maternal defense, injury, or predator presence. Its production involves coordinated endocrine, neural, and muscular mechanisms designed to convey urgency, deter rivals, and mobilize group responses.