Pete,
Here you go. You can interpret the riddle as you like. The 'spoke once bit' is referring to the male tortoise - ie it hatched, didn't get eaten, and only mated once in it's life. It doesn't necessarily have to 'speak' when it is born. There is no time reference in the riddle.
Otherwise it could be referring to a 'squeak' it made as it was eaten by the buzzard. I prefer the first option.
Whoever came up with this riddle had a literary mind and left alot to be interpreted by the person trying to solve it.
Where the people above got turtle from I have no idea - there are no reference to turtles in this chapter and it is quite obvious that this is where the riddle originated. Please enlighten me....or did you just make it up...lol
http://human-nature.com/darwin/voyage/chap17.html
"The tortoises, when purposely moving towards any point, travel by night and day, and arrive at their journey's end much sooner than would be expected. The inhabitants, from observing marked individuals, consider that they travel a distance of about eight miles in two or three days. One large tortoise, which I watched, walked at the rate of sixty yards in ten minutes, that is 360 yards in the hour, or four miles a day, -- allowing a little time for it to eat on the road. During the breeding season, when the male and female are together, the male utters a hoarse roar or bellowing, which, it is said, can be heard at the distance of more than a hundred yards. The female never uses her voice, and the male only at these times; so that when the people hear this noise, they know that the two are together. They were at this time (October) laying their eggs. The female, where the soil is sandy, deposits them together, and covers them up with sand; but where the ground is rocky she drops them indiscriminately in any hole: Mr. Bynoe found seven placed in a fissure. The egg is white and spherical; one which I measured was seven inches and three-eighths in circumference, and therefore larger than a hen's egg. The young tortoises, as soon as they are hatched, fall a prey in great numbers to the carrion-feeding buzzard. The old ones seem generally to die from accidents, as from falling down precipices: at least, several of the inhabitants told me, that they never found one dead without some evident cause."
Anyway - sorry for any hair loss. The answer is tur.....tortoise...lol