In a surprising urban wildlife partnership, stingless bees are unwittingly providing midnight snacks for nectar-loving bats.
Researchers report the first observed instance of a bee facilitating sap access for a bat, detailed in a study published December 2025 in Ethology. This cross-species boost, spotted in southeastern Brazil, highlights hidden trophic links in city ecosystems and could reshape how we view facilitation between distant animal groups.
Facilitation happens when one organism helps another without getting much in return, like easing access to food or shelter. It’s common among similar species but rare across big taxonomic divides, especially between invertebrates and vertebrates. Most examples involve birds trailing ants for flushed-out insects or bats roosting in termite nests. Trophic facilitation, where one boosts another’s food supply, is even scarcer.
In this case, the action unfolded in a coastal residential area of Guarujá, São Paulo, over six days in October 2017. Three Senna macranthera trees, laden with mature fruits but no flowers, lined a sidewalk. During the day, groups of 3 to 7 stingless bees (Trigona spinipes) scraped the fruit pedicels with their mandibles, creating small wounds that oozed sap. The bees returned to these spots or made new ones, drawing occasional ants and flies too.
Come nightfall, nectarivorous bats (Glossophaga soricina) swooped in. They hovered briefly and licked the sap from the lesions or where it dripped down the pods, without perching or making wounds themselves. Visits were short and frequent but tapered off after 8 p.m. The observer captured it all in sequential photos, ruling out bats as the wound-makers.
This setup fits indirect trophic facilitation: the bees’ rasping exposes a carbohydrate-rich resource that the bats exploit. “This observation provides robust evidence of indirect trophic facilitation between an invertebrate and a vertebrate, mediated by sap exudation in a native tree,” the researchers note.
The sap might offer more than energy. Senna species pack antimicrobial compounds like anthraquinones, which could help bats fend off parasites, a form of self-medication seen in other animals. But the main draw is likely the sugar boost for these flexible foragers, who thrive in urban spots by tapping flowers, fruits, and now sap.
Why here? Urban areas mix species in novel ways, fostering unexpected ties. The bees, generalists hit hard by floral shortages, turn to sap scraping. Bats, tolerant of human habitats, capitalize on them. “This case contributes novel, visual evidence that bats may exploit non-floral exudates when made accessible by other taxa,” the study adds.
Such overlooked interactions could be key in fragmented landscapes, urging more peeks into how urban critters reshape food webs. As cities grow, spotting these links might reveal broader ecological roles for everyday behaviors.
Citations: Ethology. DOI: 10.1111/eth.70034
