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[em1LL]

Hi all!

How much grass tiles each grazing animal should have to prevent it from fighting with other animals?

Thanks in advance.

[Dowly]

Well... when they stop fighting, you've got the right size pasture. 

[Urist McKoga]

See the values in : http://dwarffortresswiki.org/index.php/DF2012:Grazer

They only fight if they share the same pasture and are fighting for the same food tile (cave moss,floor fungus, grass etc). So even recommended pasture size can have fights, you have to create smaller pastures and assign to each animal if you really want to avoid any combat.

[Larix]

The numbers in this list are massively inflated. AFAIK, they were based not on direct observation on what size pasture can feed an animal, but rather on a chain of extrapolations.

We really should revise that table and get some accurate numbers for it. My current advice would be "look at the table and allocate _half_ the suggested size per animal".

You can cut all those area numbers in half, and you'll still have much more than needed for each animal. I haven't explored this thoroughly, but a horse in a pasture of 45 tiles has either barely not enough or barely enough (got to all tiles bare floor on occasion but hasn't gone hungry yet). I had seen that a 10x10 pasture can reliably feed two horses, but not three. As another example, i have some rather large wool farms. 23 sheep and alpaca (mixed) on a 21x15 pasture (315 tiles, ~14 per animal) keep about 1/5 of the area stripped, the rest is full of vegetation, most of it "dense". It looks like they could be compressed into a pasture half the size without trouble, while the wiki page suggests 20 tiles per sheep and 25 per alpaca, i.e. a size increase by about 50%. Remember that the wiki suggests those as _minima_.

Animals will start bunching up and may begin infighting when too many share a pasture; that's especially true of grazers, who tend to compete for the same patch of grass. For large grazers (horses, kine...), i'd suggest putting no more than three or four in a pasture. With smaller grazers like sheep and goats, you can get away with much larger populations, but once you get combat reports from your pastures, you better reduce pressure by making the pasture larger or relocating part of its population to a new pasture (or to your larder). More than ten sheep in one pasture can get dangerous when you keep pasture size small.

[PintOfBass]

Not all grass is created equal.  Sometimes I can have 4 Alpacas or 3 Llamas sharing an 11x11 pasture and never see a patch of bare ground and other times its dicey having only 2 per 11x11.  What does seem to be true is the grass quality is fairly consistent across a biome.  So my advice would be to have a set test that you conduct each map with the grazer of your choice.  Mine is what I mentioned above, if that seems to be ok then I keep it as is, if not then I take all the pastures out and increase the tile count per animal. 

[TruePikachu]

I would think consumption is related to the body size, which varies not only species-species but also creature-creature. And production is related to how frequently the tile is stepped on, as well as possibly biome.

In general, my rule of thumb is to forgo grazers and use hunting or nongrazers.

[Larix]

Not all grass is created equal.  Sometimes I can have 4 Alpacas or 3 Llamas sharing an 11x11 pasture and never see a patch of bare ground and other times its dicey having only 2 per 11x11.

The latter sounds like it's in a mountain biome, where grass will _never_ regrow. In any other biome, an 11x11 should be more than enough for two llamas.

You can keep grazers in mountain areas for quite a while - they'll take years, sometimes even decades, to deplete the grass. But in the very long term, it's absolutely not sustainable, because mountain grass never grows back, so all the grass that gets eaten is gone for good.

Below-surface grass seems to grow at (more or less) the same rate regardless of biome - both actual underground vegetation and grass that grows on channelled-out soil (even in deserts and badlands, which have no surface vegetation - the "two horses on 10x10 pasture" was channelled soil in a desert).

As i said, it'll need quite a bit of exploration to get decent numbers for grazing area. I doubt that creature size is very important - "GRAZER:x" is a numerical parameter, and lowering/increasing it has been observed to directly change the food intake, so that e.g. elephants with a high GRAZER value can feed themselves without trouble. Creature size is certainly worth testing, though.

[wierd]

So, what you are saying is that there is an opportunity for raw basic science here?

DFHack could be quite useful, as it can produce uniform areas of "Grass". (using tiletypes to paint grass produces generic grass, which grazers can still consume.) It can also spawn creatures with an appropriate script installed. (Thanks Putnam!)

I dont know of any targeted scripts for assigning arbitrary values to creature size on a generated creature though. We can probably make up for this with exhaustive data collection with a large spread of animals though.

It should be entirely possible to get all the data required with just a few years of fortress mode time invested on each target biome of interest.

[Sadrice]

For an easy way to measure grass consumption, why not use a mountain biome as your measurement pasture.  Pasture an animal in a 5x5 pasture (100 units of grass at 4 per tile, assuming all full, use df hack to make the, full if necessary) and measure the amount of time until the grass is entirely depleted, or count remaining grass units after a set length of time.  Ideally using a large battery of test pastures in case of any randomness in the results.


To get a figure on how quickly grass grows, if that's not already quantitatively understood, use df hack or some other method to clear a 5x5 area of grass, and wait until it has fully regrown (or wait some length of time and count grass tiles present and do the math, but whatever).

[Larix]

That might lead us back to wild extrapolation; in an actual pasture, trample, replenish, consumption all happen at the same time, partially deterministically and partially stochastically. The approach that got all those exaggerrated numbers worked pretty much like this - observe "replenishment rate", observe "consumption rate", combine them into some sort of metric. Unfortunately, the numbers it gave fail the field test - observed needed pasture sizes are a lot smaller practically everywhere outside of desert biomes.

A few numbers from field tests:
One horse can barely keep a 5x9 aboveground pasture mostly-to-entirely bare (biome with fairly lush vegetation, but i don't know the exact metric - something in the "dense" range), anything larger will keep untouched grass. A yak bull can get into "hungry" status on an 8x8 underground pasture, but will reach a viable equilibrium on a 9x9. Goats - ho hum. A 4x4 pasture was _not depleted_ by five goats (just over three tiles per animal), but it wasn't viable in the long run, because they started infighting. Two goats in a 2x3 seem able to survive so far. Those are very few actually quantified data, but they all point in the same direction - the minima for pasture size in the field seem to be about 1/3 of the values given on the wiki. Vegetation below standard ground level (both cave vegetation and aboveground plants on channelled soil) seems to grow at the same rate regardless of biome, so might be a good "standard" reference.

My numbers so far are:
yak - minimum 9x9, 80 tiles. Recommended 10x10, 100 tiles.
horse - minimum 5x9, 45 tiles. Recommended 7x8 or 8x8 (56 or 64)
goat - minimum? hard to measure, probably 1x3, 3 tiles. Recommended 2x2, or three to four in a 4x4 pasture.

The tentative rule-of-thumb for minimum pasture size (underground) would be 7000/grazer value for number of tiles, large (llama and bigger) grazers only. Going by the experience with the goats, bolstered somewhat by what i've seen of other small grazers like sheep and alpaca, pasture requirement is probably not directly (inversely) proportional to grazer value, since at the limit, it seems that grass is kept down less by consumption and more by trampling (when the animal going to a re-grown patch stomps over all the ground in between). The smaller grazers, which take longer to consume a patch of grass, seem to move about in search of fresh grass much less.