They lose 1 point of food every 15 seconds, so to time how long until they start starving, multiply their current amount of food by 15 and then divide by 60 twice. This will give you the number of hours left untill the food stat reaches 0.
Equation:
((15 x food)÷60)÷60

I used a very effective method but it sounds like a joke, but it works fine: use a gasbag, 20-30 vegatible cakes for gasbag healing and like 10-15 stacks berries for gasbag food and at least 2 hazard suits. You can easily fly down to the spots where the nests are, then fly to the nests, steal the eggs, fly to the entrance of the complex and repeat it. Important: if you want to play safe, then only take the nests on the highest spots, because if you go for the lower spots, it can happen, that an army of drakes stuck you into a nest and your gasbag and you will die. If the cakes are empty, you have to go back to the "non radiation zone", cause after a time without healing the radiation is too much dmg for the gasbag. But this method only works fine, if you a) can control the gasbag and b) the gasbag should have at least 6-10k hp, 2-2,5k stamina and over 100k oxygen. And don't forget to regain stamina and gas every time.

Obtaining this creature will require you to enter the tek trench where puprle liquid and the nests of these creatures lay past the bioluminescent chamber, there you must steal an egg and raise in a cold environment feeding it nameless venom you can get by killing nameless

The rock drake trench can be found at 57,56 at the area of the map called grave of the lost. Recommend u bring a glider suit and climbing picks and if u have a good tame to fight the drakes. In the wild they can be invisible and can glide in the wild so watch out also wear a HAZARD SUIT it's needed. Lastly there are a lot of nameless in the area so bring a light source. Good luck and ohh it needs to be cold to hatch so air cons

Their eggs are the opposite of wyverns, they need to be very cold to hatch. It took mine 20 air conditioners to get to the right temp! You feed them Nameless venom when they hatch.

DO NOT USE 1 POUNT IF FOOD EVERY 15 SECONDS IN YOUR EQUATIONS (for raising rock drakes) I’ve seen many comments that say this but i have tested it and the babies lose 1 point of food every 10 seconds! If you assume it as 15 seconds your baby will likely die!

They are really easy to raise. In 10 minutes they lose about 57 food and in 1 hour they lose 343 , also , 1 nameless venom gives 400 food.

The easiest way to get and egg is to find someone taking a basilisk.

Best method for stealing eggs: Tame 2 megalosaurus (opposite gender) and breed them. Your imprinted baby will be the one you ride on. Then, you take your imprinted megalo and the opposite gender for mate boost. Btw each megalo should have at least 14k hp and 320 melee. Use this method for easy first drake.

Another way to do the math for food stat loss when raising rockdrakes. They lose 1food per 15 seconds. you lose 4 food every minute. (My advice go up to 5 if your paranoid like me and get Arked. 60mins x 4food = 240, (240 is the total food stat loss per hour.)
Now take your total food stat and ÷ by 240, and you will have a correct time as well.

You have to steal an egg like a wyvern. I used a lot of ziplines and a high level ravager to get down there, used the pick to climb up to an egg and ran. The drakes nearby WILL aggro on you. I got on my ravager and ran away on the ziplines. Make sure you have a hazat syit to protect you since there is radiation down there.

for me, in a metal box it took 16 air cons

Real men get the eggs alone with climbing picks and glider and kill the mom with their bare hands like men

You can't tame a Rock Drake by knocking it unconscious. You need to find their glowing nesting caverns and steal one of their eggs to hatch your very own Rock Drake.

Use climbing pick's to climb up to a nest and make sure that there are no Drake's then take the egg and glide out on a wingsuit. You can out-glide a Drake.Stay clear of the water and a have a shoulder pet to stop the Nameless. Have a hazard suit on and you need like 20 air conditioning units to make it hatch. Feed it Nameless venom to raise.

In one of the explorer notes of Mei Yin, she wrote that she tamed one of these guys with KO method using tranq arrows

I took 2 hazmat suits 2 gliders 2 zip line motors 20 zip line and almost didn't make it out. Grab red Crystal when you're down their you'll need 100 for the saddle

To continue from my previous formula of food x 10 or 45 ÷ 60 ÷ 60 one venom replenishes 400 food. At ~18% OF TOTAL FOOD is when my rock drake ate, for me this was 846/4800 but i read it would eat at 10%. Here's a simple formula to find when yours will eat based on 18% : (max food) x 0.18 = eat.

To get an egg you can just glide into the caves with the hazard suit with a wingsuit equipped. U have to glide into the golden Cave and get an egg out of a nest. Now immediately jump off the nest and use the suit to glide to one of the metal portals. Stay calm and use some climbing picks(I had 15 and I NEEDED all)to get out of the caves. Have fun and enjoy.

After can find the Eggs at 57 Lat 67 Lon once you have the egg back at your base you will need to gather Nameless Venom in order to feed the baby drake