The longest tongue (relative to body length) ever reported in a mammal resides largely inside the ribcage of a recently discovered nectar-eating bat in the cloud forests of Ecuador. The tongue of the tube-lipped nectar bat (Anoura fistulata) is 1 1⁄2 times as long as its body.
Nathan Muchhala of the University of Miami (Florida) discovered the new species during a study supported by a BCI Student Research Scholarship (BATS, Summer 2005). He concludes that this remarkable bat evolved in tandem with an extremely long, trumpet-shaped flower. The flower averages about 3 to 3 1⁄2 inches (8 to 9 centimeters) long, which turns out to be roughly the length of the tube-lipped nectar bat’s remarkable tongue.
In a spectacular example of co-evolution, as the Centropogon nigricans flower became longer over millennia, the bat’s tongue apparently elongated to reach the nectar stored at the base of the ring of petals. “It is,” Muchhala says, “like a cat being able to lap milk from two feet away.”
In return for the nectar, the bat pollinates the flowers – and it apparently is the only species that can do so. Such extreme specialization is rare, and this is the only example so far documented in flowers pollinated by bats.
Managing such an extraordinary tongue requires unusual morphology, Muchhala said. In other nectar bats and most mammals, the base of the tongue is attached to the base of the oral cavity, and the tongue is stored in the mouth. In the tube-lipped nectar bat, however, the tongue continues – inside a sleeve of tissue – down through the neck and ends up between the heart and sternum.
Muchhala’s Ph.D. research explored co-evolution between nectar bats and bellflowers in the cloud forest. For 129 nights, he and his team netted bats and recorded video of bats visiting flowers. They identified the pollen on the captured bats’ fur and in their feces to positively link the bats and flowers.
The most common pollinators were Geoffroy’s long-nosed bats (Anoura geoffroyi) and tailed tailless bats (A. caudifera), but the pollen of C. nigricans was never found on either species – only on tube-lipped nectar bats. And during 55 hours of videotaping, no other animals visited these flowers, suggesting that C. nigricans is completely dependent on the pollination services of tube-lipped nectar bats.
Measuring bats’ tongues was a challenge. Muchhala trained captive bats to drink sugared water from a modified straw. The Geoffroy’s long-nosed and tailed tailless bats were able to reach the water down to about 1.5 inches (3.9 centimeters). The tube-lipped nectar bat was still drinking at 3.3 inches (8.5 centimeters).