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.
To calculate how many acs you need to hatch, find the range between your temperature in the hatching area, and -80. Divide this by 6, and boom, that's how many you need. Get an extra on just in case of temperature changes.
1 ac=6 degrees Celsius of insulation
100 melee on a otter= 2 degrees Celsius of insulation
With TLC Update 3 out and wyverns are now breedable, I would definitely recommend getting a 190 high base stat breeding pair ready for the future as I don't see why they wouldn't make Rock Drakes breedable as well.
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
When you enter the trench, you need a hazard suit and if the nameless are too annoying, get a light pet. Also, when you see a drake, kill it if you can. The nests are in the yellow lighted area and the eggs spawn in the cliffs. When you get the egg, climb out of there and run back to the portal. Then, go to the nearest obelisk at 20 Lat, 80 Long