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