The honey possum is the only mammal that survives entirely on nectar and pollen.

Nature · Published 3 October 2026 Swipe more like this →

In short: This tiny Australian marsupial, weighing less than a mouse, possesses the longest sperm in the mammal world. It is a specialized pollinator that has evolved alongside its favorite plants for forty million years, navigating the night with trichromat vision to find the flowers it needs to survive.

The honey possum, or noolbenger, is a unique marsupial endemic to the southwest of Australia. Unlike most mammals, which rely on dichromat vision, this species utilizes trichromat vision to detect the bright yellow inflorescences of plants like Banksia attenuata. Its physical form is highly specialized for its diet: it features an elongated snout, a tongue covered in brush-like papillae, and reduced teeth that function as a fine combing surface. These adaptations allow it to act as a crucial keystone pollinator, effectively conveying pollen loads across the coastal sands of the region.

Reproduction in honey possums is as remarkable as their diet. Females are promiscuous, often carrying embryos from multiple fathers simultaneously. This intense competition has driven the evolution of extreme reproductive traits; males possess some of the largest testicles relative to body mass of any mammal, and their sperm, measuring 365 micrometres, is the longest known in the animal kingdom. Their young are the smallest of any mammal at birth, weighing just 0.005 grams. Development is closely tied to food availability and day length, with females capable of pausing embryonic development through a process known as diapause.

Despite their specialized niche, honey possums are resilient, capable of entering states of torpor to survive food shortages or cold weather. However, they face modern threats. The species is susceptible to Phytophthora cinnamomi, a pathogen that causes forest dieback and destroys the plants they rely on for year-round sustenance. Furthermore, while they show some resilience to wildfires, increased fire frequency and intensity, often exacerbated by global warming, pose significant risks to their habitat. Understanding these creatures has required decades of study, from early 19th-century collections to modern biological research that began in earnest in 1974.

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