The idea of a sow “singing” to her piglets points to the complex world of animal communication. While pigs do not vocalize in a melodic sense, mother pigs, or sows, use a highly structured form of parental communication. This behavior is not a lullaby but a specialized acoustic signal—a rhythmic series of grunts designed to coordinate the crucial nursing process. Understanding this “sow song” requires looking closely at the specific sounds pigs use and the biological purpose they serve.
Defining the “Singing” Sound
The sound commonly described as a sow’s “singing” is scientifically identified as a series of rhythmic, low-frequency grunts. While grunts are common in the pig’s repertoire, the nursing grunt is distinct, possessing a specific acoustic profile. These grunts are short, lasting about 0.15 seconds, and have a low fundamental frequency, often around 750 to 1000 Hz.
This structured calling follows a predictable pattern. It begins at a slow, regular interval as the piglets gather at the udder and start massaging it. The rate of grunting then accelerates rapidly, acting as an auditory countdown. The sow’s vocalization is loud, registering around 75 dB, and its rhythmic nature makes it an effective signal.
The Function of the Sow’s Vocalizations
The primary function of the rhythmic grunting is to synchronize the entire nursing process, which occurs frequently, approximately every 50 to 60 minutes. The preliminary, slower grunts attract the piglets to the udder and encourage them to begin massaging the teats. This physical stimulation triggers the physiological sequence necessary for milk release.
The accelerating grunt rate signals the imminent release of milk, or milk let-down, a brief event lasting only 10 to 20 seconds. The sudden increase in rate indicates that the hormone oxytocin has been released.
This oxytocin surge causes the muscular contractions needed for milk ejection, signaling the piglets to switch from massaging to rapid sucking.
The sow’s call also plays a role in establishing order and recognition within the litter. Piglets are precocial and quickly establish a stable “teat order,” with each piglet claiming a specific teat. The mother’s distinct vocalization aids in piglet recognition, and studies show that newborn piglets can respond to the unique sound of their own mother’s call. The communication is so effective that playing recorded nursing grunts can stimulate suckling and improve piglet survival.
Swine Communication Beyond the Sow and Piglet
The specialized nursing grunt is one facet of a complex communication system in pigs, involving more than 20 distinct vocalizations. Grunts, the most common sound, are also used in other contexts, such as signaling excitement or functioning as a contact call between herd members.
The pitch and volume of these sounds convey information about the pig’s emotional state, size, and location. High-frequency sounds like squeals and screams typically communicate fear, pain, or distress. Conversely, low-pitched sounds often indicate contentment.
Pigs also use barks, which can signal alarm, aggression, or occur during play. This broad repertoire of acoustic signals, combined with olfactory and visual cues, demonstrates that the sow’s rhythmic call is a highly evolved, situation-specific signal.