Tuesday, December 6, 2016

#ElephantTuesdays: The elephant´s feet 🐘

Free-living African elephants are estimated to walk 30 – 60 km daily (Asian elephant herds can walk 20-30 kilometers per day). They walk on different terrain types, rocks, mud, vegetation, they go through escarpments, they use their feet to dig up roots from the ground, etc. All this daily activity allows them keep their feet healthy (although to be fair enough, they might as well suffer from fractures, lacerations or even injuries resulting from landmines in the wild).  

However, if we talk about non-free living elephants, we find that foot problems are seen in more than 50% of captive Asian and African elephants at some point of their lives. The inactivity, malnutrition and unsuitable ground (concrete), very often trigger foot diseases. Although some of the foot problems could be treated, they often result in serious disabilities or even euthanasia. That’s why an appropriate foot care of the captive elephant´s feet is critical. Because of their body weight distribution, captive elephants happen to show more foot disorders on their front feet (Asians more than Africans).  

Some of the most common foot diseases in captive elephants are:
Cuticle feathering and nail abscesses

Nail cracks (source

Nail overgrowth

The elephant feet are very interesting structures, with unique mechanical and sensory functions. They are designed to support the weight of the largest land mammal with the help of subcutaneous cushions, which distribute forces when walking or standing. While standing, the weight distribution of a large African male elephant (6000 kg) is 60% (3600 kg) on the front feet and 40% (2400 kg) on the back feet. 

Besides, they are equipped with sensory receptors (Vater–Pacinian corpuscles and Meissner corpuscles) that make them the most sensitive part of an elephant's body. Elephants can detect seismic vibrations that deform the layers of the Pacinian corpuscles, sending a nerve signal to the brain. 

Both mechanical and sensory functions of an elephant's limbs enhance their ability to move through and analyze their physical environment. In the video below, the female elephant is checking the ground with her front limb.

Original video: ACP000bia8

It is thought that when elephants move their feet with a slight horizontal tendency, they are 'listening' to infrasounds, and if the movement is more vertical instead, they are just recognizing the ground. In this case, we see her moving her foot up and down.

A very interesting point here: she is using her trunk to collect something on the ground and her foot to check the plants, and this is a good example for independency, meaning that they can use their trunk and limbs simultaneously for different things.

As a curiosity: the elephant toenails grow approximately 0.5 to 1.0 cm. per month, while in humans the growth rate of toenails is 1.62 mm/month. 

Murray E. Fowler, Susan K. Mikota (2006): Biology, Medicine, and Surgery of Elephants. 
Csuti, Sargent and Bechert (2001): The Elephant's Foot: Prevention and Care of Foot Conditions in Captive Asian and African Elephants

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