How much stress do elephants feel due to weight? While we humans weigh around 70 kg, elephants weigh around 5000 kg.
My question is: While moving or standing, how many more times than humans does the elephant feel the stress due to weight?
Is there any upper limit to the weight any animal can carry?
 A: Assuming that the four legs of the elephant is equally spaced from its center of mass (which is approximately true as in reality the front limbs carry 60 % of the weight while the hind ones carry 40 %) so on average then each foot will get one-fourth of the weight ($mg/4$) of the elephant. The area of an elephant’s foot is quite large of about $0.18\ \mathrm{m^2}$. So the stress is now found by $$\frac FA=\frac{12\,262\ \mathrm{kg\ m\ s^{-2}}}{0.18\ \mathrm{m^2}}=68\,125\ \mathrm{Pa}$$
Now that for an average human of suppose $70\ \mathrm{kg}$, the average foot area is $0.03\ \mathrm{m^2}$ so you’ll find the stress now to be: 
$$\frac{343.35\ \mathrm{kg\ m\ s^{-2}}}{0.03\ \mathrm{m^2}}=11\,445\ \mathrm{Pa}$$
You can clearly see the pressure on the elephant’s foot is much higher and it can withstand this because of its muscle and tissue structure relative to the size of its body. Like even very less massive animals can withstand pressures close to this if their strength in their body structure is large relative to its body. This is very true for animals that live deep within the ocean and have specially developed bodies to withstand the high pressures at those depths due to the water above them. Like it is astounding how a tardigrade can withstand pressures up to 6000 atmospheres ($6\times10^8\ \mathrm{Pa}$) due to its highly dense and sturdy cellular structure.
