...and what is it, do you suppose, that animals would be grubbing in the earth for, normally?
It was the of that confused me. Or possibly there was a period missing. Transferred from animals would have done. Or, if there had been a period or other punctuation after the word transferred, in the use of grub in this sense predates "grub stake" by about 200 years and probably (reading between the lines here) stems from the use of the verb grub as transferred Of animals: To root, search for something in the earth, etc. , then it would have made sense to me.