Elephant Trunk’s Dexterity Revealed: Microscopic Musculature Explains Agility of the Snout

An elephant can use its trunk to lift logs and to pick up a potato chip without breaking it. This ability to demonstrate brute force and soft touch is attributed to the trunk's musculature, the most complex in the animal kingdom.

Unique Characteristics of Elephant Trunk

Just like the arm of an octopus or animal tongues, an elephant trunk is one of the few appendages that can move around without using bones. The elephant's trunk contains the most complicated muscles among the animal appendages.

The trunk is an upper lip and a nose, with two nostrils running through it. Despite its flexibility, it is also so strong that it can push down trees and lift a 700,000-pound (316,000 kg) load.

This appendage also allows the elephant to be the only animal that can snorkel independently. By extending their trunks out of the water, elephants can cross bodies of water that are too deep for less-equipped animals.

Another interesting feature of the trunk is its phenomenal sense of smell. The upper nasal cavities contain chemical and olfactory sensors in millions of receptor cells. This makes the trunk sensitive enough that an elephant can smell water from several miles away.

Dense Reconstruction of Elephant Trunk

To better understand the dexterity of elephant trunks, a group of researchers led by neuroscientist Micheal Brecht of Humboldt University of Berlin conducted the most detailed examination of the unusual snout. The findings of this study not only help explain the ability of elephants to control their trunk but can also offer new insights that can be used in designing robots with flexible appendages.

In search, the experts used an X-ray-based technique known as a computed tomography (CT) scan to study the trunk of a 6-day-old baby elephant born in the Leipzig Zoo. The young animal broke its leg and could not nurse, so the zoo veterinarians euthanized it.

The trunk was frozen and then sawed in half lengthwise. After it was thawed and stained, it was examined with a CT scanner, which has a much higher resolution than the standard equipment in hospitals. Next, the research group used software to identify the muscle bundles in four representative parts of the trunk.

Based on the in-depth study of each trunk region, the experts estimate that the entire trunk contains over 89,000 fascicles. The tip of the snout, with its "finger" and "lip," is particularly dense with almost 8000 of the tiniest fascicles. At the end of the trunk finger, the bundles measure only 2 millimeters long and just about the diameter of a human hair.

It was also noted that the trunk tip consists solely of fascicles arranged radially, probably playing an important role in fine control. Furthermore, the X-ray images reveal that the main trunk has much larger fascicles than the tip, which are arranged in two ways. Longitudinal muscles help move the entire trunk from side to side. Meanwhile, the transverse muscles spiral around the outside and help twist the trunk.

The new anatomical view unveiled in the study can help explain how the elephant manages to flex and elongate its trunk while doing its tricks. As the researchers noted, the trunk is even more complex than previously thought.