Guinea pigs are among the most commonly kept small animals, with welfare needs including social companionship that are frequently not met.
Solitary guinea pigs are in a permanent state of social deprivation that causes chronic stress detectable through physiological markers. Their vocalisation includes specific calls for social contact that are not made when companions are present. Vitamin C deficiency causes scurvy, which is painful and debilitating. Small enclosures prevent the spontaneous running and popcorning behaviour that indicates positive welfare states in healthy guinea pigs.