01 May Elephants – How Do Such Large Creatures Manage to “Snorkel”?
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On a pleasant sunny day in late July, Chundu Island guide Johannes Mankuli was taking guests for a boat ride on the broad Zambezi River on Zimbabwe’s northern border when he noticed a herd of elephants gathering in the riverine vegetation along the riverbanks.
After a while, the animals, including small calves, followed the matriarch into the water and, without any fuss, began to swim hundreds of metres all the way to neighbouring Zambia.
Soon after entering the swiftly flowing water, even the adults disappeared beneath the surface, only the tips of their trunks visible as they “snorkeled” across the river. The young, bobbing up and down as they paddled in single file, were nudged along by the adults, and before long reached the Zambian shoreline and started quietly feeding amongst the trees. The animals were no more concerned than they would have been had they crossed a road.
Most people know that elephants love water but what is less well-known is that, as evidenced above, they are capable of swimming long distances across deep lakes, dams, or rivers.
Elephants are remarkably buoyant and use their strong legs to “paddle” through water at a surprising rate. Occasionally, they may decide that water is of a suitable depth to allow them to walk along the riverbed with their bodies submerged, and again, use their trunks as “snorkels.”
The ability to snorkel while at depth is a characteristic unique to elephants amongst mammals and is made possible, in part by their long trunks, but also the design of their lungs and surrounding membranes which are able to cope with increased air pressures.
When in deep water an elephant’s lungs are several metres below the surface (female African elephants average 2.8 – 3.3 metres at the shoulder and males over four metres) but they have developed a unique physiological feature which copes with the pressure imposed by the water, an adaptation without which the lungs would be damaged.
Most land mammals have a fluid-filled membrane around the lungs (known as the pleural space) which expands and contracts during breathing to facilitate oxygen flow, but in elephants this is replaced by dense tissues connected to the diaphragm and ribcage which protects the lungs from pressure fluctuations. In other mammals the fluid membranes are vulnerable to damage from increased water pressure.
Professor John West of the University of California who first explained this anatomical feature, argues that it was an evolutionary development of what he believed to be the elephant’s aquatic origins.
(Scuba divers do not breath air at the same atmospheric pressure as that of air above the surface – to avoid damage to their lungs they adjust the air pressure in their tanks to match the surrounding water pressure. Human snorkelers can only draw in oxygen on the surface and have to hold their breath to dive deeper).
Unlike elephants, hippos can’t swim and have to hold their breath, which they can do for up to five minutes, while they run along the bottom of rivers or dams.
Unlike elephants, hippos can’t swim and have to hold their breath, which they can do for up to five minutes, while they run along the bottom of rivers or dams.
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References and further reading:
Why doesn’t the elephant have a pleural space? Prof. John West, University of California, 2002. https://pubmed.ncbi.nlm.nih.gov/11909991/
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