I had a thought while cleaning a water bottle for my gerbils. Mainly, I remembered seeing very large size such water bottles in a pet store that is affiliated with a puppy mill – bottles of the right size for a dog. I decided to collect average weights of a few different rodents and dogs. (The highest number I could find for mice was 30, but I KNOW our mice are bigger than the robos.)
Average Weights
robo hamster: 25-40 grams
mouse: 30-45 grams
gerbil: 70 grams
cat: 3-5 kg
beagle: 9-11 kg
cocker spaniel: 12-16 kg
pit bull: 10-35 kg
golden retriever: 25–34 kg
St. Bernard: 64-120 kg
Many rodents can be kept in a ten gallon terrarium, especially if you only have one (which is not necessarily smart, but let’s focus on the “one in the cage” scenario for now). A standard ten gallon aquarium has a length x depth of 20 x 11 inches or 50.8 x 27.9 centimeters, which means a “ground” area of 220 square inches or 1417.32 square centimeters. Let’s work out the ground area living space to grams ratio for a robo hamster (the smallest hamster), a mouse, and a gerbil.
Living Space to Grams Ratios (Rodents)
Robo hamster: 1417.32 cm^2 / 30 g = 47.24 cm^2 / g
Mouse: 1417.32 cm^2 / 45 g = 31.5 cm^2 / g
Gerbil: 1417.32 cm^2 / 70 g = 20.25 cm^2 / g
The worst is obviously the gerbil, with just over 20 square centimeters per gram of body weight.
The largest size dog cage that Petco sells (at least of that brand/style) is 48″ L X 30″ W X 32″ H, which is a “ground” area of 1440 square inches or 9290.304 square centimeters. Let’s work out the ground area living space to grams ratio for a few dog breeds and a cat (just for fun).
Living Space to Grams Ratios (Dogs and Cat)
Cat: 9290.304 cm^2 / 4 kg = 2.3226 cm^2 / g
Beagle: 9290.304 cm^2 / 10 kg = 0.9290 cm^2 / g
Cocker Spaniel: 9290.304 cm^2 / 14 kg = 0.66359 cm^2 / g
Pit Bull: 9290.304 cm^2 / 25 kg = 0.3716 cm^2 / g
Golden Retriever: 9290.304 cm^2 / 30 kg = 0.3097 cm^2 / g
St. Bernard: 9290.304 cm^2 / 100 kg = 0.0929 cm^2 / g
I have no idea if anyone would even try to keep a cat in an extra large dog cage, but that’s how much room they would have if they did.
As you can see, putting a dog in crate gives it way less space per weight than putting a gerbil in a small aquarium. Even in the best case scenario of a beagle in a XL cage, a gerbil has 20 times as much space, and that’s not even looking at height – it’s best to give gerbils at least some space to dig, and all of their toys, food, and water can easily be kept in the same area. Let’s do more math to see how big of a cage a golden retriever (to me that’s a medium sized dog) should have to have the same ground area as a gerbil in a ten gallon tank.
30 kg = 30000 g
30000 g * 20.25 cm^2 / g = 607,500 cm^2
607,500 cm^2 = 60.75 m^2
60.75 m^2 = 653.908 ft^2
For reference, the average one bedroom apartment in NYC is 750 square feet.
Without even looking at factors like how much territory these animals would have in the wild vs. how much is in a cage, it’s possible to say pretty definitively that keeping a mouse in a ten gallon tank is far more humane than keeping even a small dog in a crate.
I understand that people have busy lives, and sometimes it is necessary to leave a dog in a crate for a period of time. My point is that if you are leaving the dog in a crate more than out of it, you should consider changing your lifestyle or finding a better home for that dog. Even a one-bedroom apartment might really be too little space for a large dog – I’m honestly surprised humans survive in them so well.
I now feel a lot better about keeping a gerbil in a ten gallon tank – he technically has almost as much space for his size as I do!
The Complete History of the Universe: A Personal Journey 