A resident in Langstone, Hampshire, received a surprising welcome when attempting to prepare a hedgehog house for a new garden visitor. What was believed to be an empty hibernation spot for a hedgehog turned out to be a bustling nest of tree bumblebees, employing a distinctive and somewhat alarming defence strategy.
The incident occurred after a period last summer saw the loss of several local hedgehogs to road accidents, leaving a purpose-built hedgehog house vacant throughout the winter months. Recent sightings of hedgehog faeces on the patio, confirmed by camera trap footage of a distinctive adult hedgehog, prompted the resident to clean out the house and leave fresh bedding in an effort to encourage the new arrival to take up residence.
Upon tentatively lifting the lid and prodding the old hibernaculum – a sphere of barley straw and dried leaves – with a bamboo cane, a sudden, high-pitched hiss erupted. Initially mistaken for an unusual hedgehog sound, the noise intensified before a 'squadron' of gingery tree bumblebees (Bombus hypnorum) emerged from the box, heading directly for the individual.
While tree bumblebees are known for their territorial nature and willingness to defend their nests, the encounter proved less aggressive than their reputation might suggest. Despite several bees hovering and bumping against bare arms in warning, only one pursued the retreating resident, who ultimately escaped without being stung.
Further investigation revealed the source of the unique hissing sound. It is produced by worker bees vibrating their flight muscles without taking off, generating strong ultrasonic signals specifically designed to deter nest predators like mice, which seek protein-rich bee brood. This defence mechanism is triggered by vibrations and the carbon dioxide present in mammalian breath, explaining the bees' defensive reaction to the disturbance.