Why cap­tive el­lies suf­fer from sore feet

The big beau­ties have 5 toes and a large fat pad that can only work well in nat­u­ral habi­tats

The Star Early Edition - - INSIDE -

WOMEN across the world un­der­stand the pain that comes with wear­ing a new pair of high heels.

Any per­son who spends all day stand­ing at work will also know how tax­ing it can be on the feet if you’re wear­ing the wrong shoes.

So stop for a mo­ment to con­sider how ele­phants feel.

Ele­phants are the largest liv­ing ter­res­trial mam­mals. Their feet carry that huge body mass of around eight tons in the case of African ele­phants. To achieve this weight-bear­ing duty, ele­phant feet have pe­cu­liar struc­tures that can also be seen in other large-bod­ied an­i­mals like rhinoceroses.

A close-up of the ele­phant foot shows ele­phants have five toes, the tips of which are in con­tact with the ground. They also have a large fat pad – equiv­a­lent to the hu­man heel – that fills the shape be­hind the toes.

The pad has the abil­ity to spread out and po­ten­tially re­duce pres­sure when the foot hits the ground, sim­i­lar to the hu­man heel in bare­foot run­ners. Ele­phants also have en­larged false toes, or predig­its, that are em­bed­ded on the pads. These also en­sure pres­sure is shifted from the sole to the rest of the limb.

Fos­sils of large-bod­ied an­i­mals show a no­tice­able cor­re­la­tion be­tween body weight, the pos­ture of the toes and the devel­op­ment of the fat pad.

Ap­prox­i­mately 40 mil­lion years ago ele­phants had small body masses (less than 2 000kg) and their toes were flat. As ele­phants started grow­ing big­ger than 2 000kg they adopted more up­right toes, larger fat pads and pre-dig­its. The as­sump­tion is that the fat pad de­vel­oped in large-bod­ied land an­i­mals like ele­phants as a mech­a­nism to re­duce foot pres­sure while sup­port­ing their large body mass.

The pad works well for ele­phants liv­ing in nat­u­ral en­vi­ron­ments with am­ple space to move and for­age. In the wild, ele­phants ex­er­cise their feet by walk­ing on rocks, dig­ging around and by rub­bing their fat pads against the ground. These ac­tiv­i­ties keep their feet moist and their fat pads stay sup­ple. They also serve as nat­u­ral pedi­cures, trim­ming an ele­phant’s heels.

But this isn’t true of ele­phants kept in cap­tiv­ity. As a re­sult, they suf­fer ex­ces­sively from var­i­ous feet ail­ments which of­ten turn out to be fa­tal.

Re­search on ele­phants kept in semi-nat­u­ral habi­tats has shown that both Asian and African species con­cen­trate the low­est pres­sures un­der­neath the fat pad and the high­est pres­sures on the out­side part of their feet.

The re­duc­tion of foot pres­sure un­der­neath the fat pad can be at­trib­uted to the com­pli­ance of the pad which po­ten­tially func­tions as a shock ab­sorber and pres­sure dis­trib­u­tor.

Ele­phants are of­ten kept in cap­tive en­clo­sures to pro­tect them against poach­ers and as tourist at­trac­tions. But an­i­mals kept in en­clo­sures with hard grounds (like con­crete or tar­mac) and small spa­ces can’t ex­er­cise their feet.

Hard sur­faces with floors cov­ered in urine and fae­ces can cause in­fec­tions around the pad. A cracked or in­fected fat pad can’t ab­sorb pres­sure ef­fec­tively, mak­ing the out­side part of the foot more prone to dis­eases. The most com­mon prob­lems are toe­nail cracks, sole over­growth, trauma, os­teomyeli­tis, anky­lo­sis of the joints and os­teoarthri­tis. It is es­ti­mated that 50 per­cent of cap­tive ele­phant deaths are caused by these af­flic­tions.

A re­cent study in Asian and African ele­phants in north Amer­i­can zoos es­ti­mated that ele­phants ex­posed to hard sur­faces for four hours each day were more likely to de­velop joint stiff­ness or lame­ness. This was com­pared to those ex­posed to hard sur­faces for two- and-ahalf hours a day.

An­other study into the qual­ity of zoos in the UK found that 80.4 per­cent of a sam­ple of ele­phants kept in en­clo­sures with hard ground had foot prob­lems rang­ing from cracks to in­fec­tion.

Man­ag­ing foot dis­eases is chal­leng­ing be­cause they of­ten only be­come ev­i­dent when they have pro­gressed to in­cur­able stages. Di­ag­nos­tic tech­niques like imag­ing are ex­pen­sive and in most cases re­quire gen­eral anaes­the­sia. Imag­ing or other hands-on meth­ods are also im­prac­ti­cal in most sit­u­a­tions.

There are a few things that can be done to keep the feet of cap­tive ele­phants healthy.

Wher­ever fea­si­ble, en­clo­sures should try to repli­cate the en­vi­ron­ment of a nat­u­ral habi­tat and re­duce an ele­phant’s ex­po­sure to hard sur­faces.

Foot trim­ming is a pop­u­lar foot care method to re­move cracks and div­ots when ele­phants walk in less nat­u­ral habi­tats. But trim­ming pro­to­cols vary and their ef­fect is still un­known. Pres­sure plat­forms – elec­tronic sys­tems with sen­sors that mea­sure foot pres­sure dur­ing dy­namic (walk­ing) or static (stand­ing) ac­tiv­i­ties – are one way to go. They could be used to help keep­ers make bet­ter and more in­formed de­ci­sions to avoid af­fect­ing the me­chan­ics of the ele­phant’s foot.

These pres­sure plates could also be used as a di­ag­nos­tic tool so that foot dis­eases are picked up ear­lier, just as po­di­a­trists use pres­sure map­ping to di­ag­nose and treat hu­man foot dis­or­ders.

Im­ple­ment­ing these prac­ti­cal mea­sures would help en­sure that ele­phants held in cap­tiv­ity don’t suf­fer un­due stress and pain. – The Con­ver­sa­tion Olga Pana­giotopoulou is a lec­turer in anatomy at the Univer­sity of Queens­land. She is also a re­search af­fil­i­ate with the Rory Hens­man Con­ser­va­tion and Re­search Unit (RHCRU) in Lim­popo, South Africa.

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