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How large of an area in acres would a large sauropod (Apatosaurus) need to maintain itself while also not eating all of the vegetation within the area.

So basically how large of a forested area would I need that could support a sauropod indefinitely, without needing extra foliage put into the area?

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  • $\begingroup$ That depends on a lot of things: tree count, type, age just from start. And we know not that much about sauropod. $\endgroup$ – Artemijs Danilovs Nov 22 '18 at 1:23
  • $\begingroup$ How big your apatosaurus is as their mass range is huge. $\endgroup$ – Artemijs Danilovs Nov 22 '18 at 1:52
  • $\begingroup$ Couple of square meters in the freezing cold of Antartica. Put the lizard under ice, and it won't consume anything. $\endgroup$ – NofP Nov 23 '18 at 9:29
  • $\begingroup$ Related: Where to Keep Your Dinosaur? $\endgroup$ – Kyyshak Nov 23 '18 at 9:41
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It depends

How much edible biomass does a forest generate?

This highly depends on what portion of the foliage is edible to a dinosaur. Since we don't really know how efficient a dinosaur's metabolism is, and we don't know how good they were at eating things like sticks, it is hard to say. But we can do some estimates.

First, Kloeppel, et al., 2007 as some estimates of net primary productivity for forest-dominated ecosystems. Here are some minimum and maximum calculated values from Table 1 of that paper:

                   Annual Net Primary Productivity (g/m^2)
Forest Type               Minimum        Maximum
Boreal evergreen             120            439
Boreal deciduous             169            635
Temperate evergreen           60           1555
Temperate deciduous          230            555
Tropical evergreen           140           1505 

So there is wide variety in the mount of green biomass generated by such forests. The percentage of what a forest generates that a sauropod could eat is also variable. In an evergreen forest of juniper and pinyon pine, in the foothills of the Rockies, 100% of the biomass would be within the distance that a Sauropod could reach. But in an old growth Virginia hardwood forest, the trees would all be 100 feet+ and maybe only 10% of the biomass would be accessible to a sauropod. Also consider that a sauropod isn't the only creature eating in a forest. Bugs will get theirs, squirrels or other similar creature will eat acorns and seeds, etc.

Let us use a range of assumptions then. The worst case scenario would be something like 10 g/m$^2$ of edible biomass, the best case something like 200 g/m$^2$.

How much does a sauropod need to eat?

The problem with a bulk biomass calculation is that there is no accounting for nutrition. You need to eat a lot less mass in leaves if you can get good nutrition from acorns.

But, ignoring that problem, let us assume that a sauropod scales up linearly from an elephant. An elephant in the wild eats something like 250 kg of biomass each day. Now, lets assume a sauropod is 8 times as massive as an elephant (so elephants average about 3 tons, and apatosaurus about 24 tons). Then an apatosaurus needs to eat 2000 kg of biomass each day.

Conclusion

For our worst case forest, that is 20 hectares; for the best case, 1 hectare. That is the total per dinosaur, so a group of dinosaurs would have to multiply by group size....a 'family' of 10 sauropods would need 10-200 hectares. Then we also have to multiply by some 'bad conditions' factor. If food supply is lower in a bad year, a dry summer, or what have you, then you would have to account for that in the area needed.

Overall, I think it is reasonable to expect something in the range of 5-100 hectares per single sauropod, depending on the fertility of the local soil, whether or not the local biomass is accessible to the dinosaurs, etc.

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    $\begingroup$ James Farlow (1987) calculates that an Apatosaurus-sized dinosaur about 35 t (34 long tons; 39 short tons) would have possessed 5.7 t (5.6 long tons; 6.3 short tons) of fermentation contents.[66] Assuming Apatosaurus had an avian respiratory system and a reptilian resting-metabolism, Frank Paladino et al. (1997) estimate the animal would have needed to consume only about 262 liters (58 imp gal; 69 U.S. gal) of water per day.[63] (wiki) $\endgroup$ – theRiley Nov 22 '18 at 2:59
  • $\begingroup$ yields ~5000 kg in the gut, assuming a 3-day digestion period, yields ~1700 kg/day $\endgroup$ – theRiley Nov 22 '18 at 3:06
  • $\begingroup$ @theRiley First, you should link your references, at least to a citation; took me like 15 minutes to determine what papers you were referring to. Second, I found the Farlow reference but the Paladino reference is in a book, I can't look it up in my university journal account, and don't see it available online anywere. So I can't comment on what it says. But how do you go from 5.7 t in the gut to 5 kg in the gut? You must mean the estimate is 1.7t = 3400 kg per day. In that case, not too different from what I estimated. $\endgroup$ – kingledion Nov 22 '18 at 3:24
  • $\begingroup$ was just trying to help with a slight bit of different rigor directly related to the genus. 5.6 long tons fermentation contents => ~5000 kg in the gut. (I) assume a three day fill/digest process => ~1700 kg/day intake, for a 34 long ton beast. i did not drill down to the underlying reference. you are welcome for the upvote $\endgroup$ – theRiley Nov 22 '18 at 4:43

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