Tiny warm blooded lemmings are the primary consumers. A collared lemming weights about 40 grams (1.4 ounces).

I go to Some Animal Weights and Caloric Requirements on Earth.  I see that a mouse living in a lab and weighing about 40 grams needs 20 Kilocalories a day. But this little mouse is not living in below freezing temperatures, is not running from predators, and is probably not reproducing frantically, as the lemming is. I will guess that a lemming needs double that, say 40 calories a day to live and metabolize. (This is purely a guess and may be very far off indeed!)

This lemming is going to be alive all year, and it will not hibernate. It needs to eat every day. So 40 Kilocalories a day for 365 days means that the lemming will need about 14,600 Kilocalories in a year.

So how many square meters does the lemming need for a year?

14,600 Kilocalories                       =
600 Kilocalories per  square meter per year.

24.3 square meters

to support one lemming for one year.

I put in 25  to make the math easier.

From this you can see how much space your predators need.

If an owl eats 12 lemmings a day, and each lemming needs 25 square meters a year, how many square meters does it take to support an owl?

How many owls can live on a square kilometer?

Note that the predator numbers here are about the animals that get eaten, not about the community of animals necessary to keep producing the animals that get eaten. As a guess, I would suggest using only half or even a third of the predators per Kilometer to allow for a continuing producing community.

Lemmings reproduce rapidly. If you are doing this with wolves and elk (large animals that produce one calf annually) I would guess that wolves could eat only 5 to 10% of the elk herd without driving it to extinction.

Tiny warm blooded lemmings are the primary consumers. A collared lemming weights about 40 grams (1.4 ounces).

I go to Some Animal Weights and Caloric Requirements on Earth.  I see that a mouse living in a lab and weighing about 40 grams needs 20 Kilocalories a day. But this little mouse is not living in below freezing temperatures, is not running from predators, and is probably not reproducing frantically, as the lemming is. I will guess that a lemming needs double that, say 40 calories a day to live and metabolize. (This is purely a guess and may be very far off indeed!)

This lemming is going to be alive all year, and it will not hibernate. It needs to eat every day. So 40 Kilocalories a day for 365 days means that the lemming will need about 14,600 Kilocalories in a year.

So how many square meters does the lemming need for a year?

14,600 Kilocalories                       =
600 Kilocalories per  square meter per year.

24.3 square meters

to support one lemming for one year.

I put in 25  to make the math easier.

From this you can see how much space your predators need.

If an owl eats 12 lemmings a day, and each lemming needs 25 square meters a year, how many square meters does it take to support an owl?

How many owls can live on a square kilometer?

Note that the predator numbers here are about the animals that get eaten, not about the community of animals necessary to keep producing the animals that get eaten. As a guess, I would suggest using only half or even a third of the predators per Kilometer to allow for a continuing producing community.

Lemmings reproduce rapidly. If you are doing this with wolves and elk (large animals that produce one calf annually) I would guess that wolves could eat only 5 to 10% of the elk herd without driving it to extinction.

 Animal Food KCal if Eaten KCal Needed Per Day KCal Needed Per Year KCal Gained per One Square Meter Total Numbers of Square Meters Needed Per Day Total Numbers of Square Meters Needed Per Year Square Kilometers needed per year (divide by 1000 x1000) Animals per Square Kilometer lemming plants 40 14,600 600 only 7% of 1 square meter 25 .000025 40,000 Snowy Owl 12 lemmings 12 *25= 300 300*365= 109,500 .11 9 Arctic Fox 30 lemmings 30 *25= 750 750 *365= 273,750 .27 3

However, it is obvious that if a predator's range (feeding area) is does not yield enough food, the predator will starve. If a predator has to spend more Kilocalories going to find food than is in the food he/she finds, the predator cannot live there.

There is also the complicating factor that the predator has to find a mate, and also find more food to feed his/her young.

The predators are the arctic fox (5 -10 lb) and the snowy owl. 2- 4 pounds (eats about a dozen lemmings a day)

1 0z meat = 100 Kilocalories
 Life Form Needs ? KCalories per Day Needs Calories per Year Needs ? Square Meters per Year at 600 Kcal each weighs Caloric Content per Gram Caloric Content if Eaten 3 Kcal * weight in grams Calories per year Calories if eaten lemming 40 40 *365 =14,600 25 40 grams 3 Kilocalories 3*40 = 120 Kcal 121.67 Snowy Owl 12 lemmings @ 120 Kcal= 1440 1440 * 365 = 525,600 Kcal per year 12 lemmings * 25 sq meters * 365 days = 109,500 sq meters 2 - 4 lbs 3 lbs = 1,361 grams 3 Kilocalories 3* 1361= 4,083 Kcal 128.73 Arctic Fox 30 lemmings (?) * 120 Kcal =3,600 3600 * 365 = 2,394,000 Kcal per year 30 lemmings * 25 sq meters * 365 = 273, 750 sq meters 5 - 10 pounds 7 pounds = 3,175 grams 3 Kilocalories 3*3175 = 9,525 Kcal
 Animal Food KCal if Eaten KCal Needed Per Day KCal Needed Per Year KCal Gained per One Square Meter Total Numbers of Square Meters Needed Per Day Total Numbers of Square Meters Needed Per Year Square Kilometers needed per year (divide by 1000 x1000) Animals per Square Kilometer lemming plants 40 14,600 600 only 7% of 1 square meter 25 .000025 40,000 Snowy Owl 12 lemmings 12 *25= 300 300*365= 109,500 .11 9 Arctic Fox 30 lemmings 30 *25= 750 750 *365= 273,750 .27 3

However, it is obvious that if a predator's range (feeding area) is does not yield enough food, the predator will starve. If a predator has to spend more Kilocalories going to find food than is in the food he/she finds, the predator cannot live there.

There is also the complicating factor that the predator has to find a mate, and also find more food to feed his/her young.

The predators are the arctic fox (5 -10 lb) and the snowy owl. 2- 4 pounds (eats about a dozen lemmings a day)

1 0z meat = 100 Kilocalories
 Life Form Needs ? KCalories per Day Needs Calories per Year Needs ? Square Meters per Year at 600 Kcal each weighs Caloric Content per Gram Caloric Content if Eaten 3 Kcal * weight in grams Calories per year Calories if eaten lemming 40 40 *365 =14,600 25 40 grams 3 Kilocalories 3*40 = 120 Kcal 121.67 Snowy Owl 12 lemmings @ 120 Kcal= 1440 1440 * 365 = 525,600 Kcal per year 12 lemmings * 25 sq meters * 365 days = 109,500 sq meters 2 - 4 lbs 3 lbs = 1,361 grams 3 Kilocalories 3* 1361= 4,083 Kcal 128.73 Arctic Fox 30 lemmings (?) * 120 Kcal =3,600 3600 * 365 = 2,394,000 Kcal per year 30 lemmings * 25 sq meters * 365 = 273, 750 sq meters 5 - 10 pounds 7 pounds = 3,175 grams 3 Kilocalories 3*3175 = 9,525 Kcal