Stump the librarian: “What is the animal to human ration in the United States?”

Dearest readers,

This week there was the luxury of choosing between several intriguing queries—if yours is not featured here, fear not!  Your time will come.


M writes in with “What is the animal to human ratio in the United States?”

Tricksy, M, very tricksy.  There are several variables to figure out, however, before The Librarian tackles this question.  First, what is meant by “animal.”  Are we talking domestic animals?  Wild?  How do you feel about invertebrates?  (The Librarian prefers to pretend they don’t exist.)

Any hard figure given for this answer will necessarily be a best guess and not fully accurate because, well, rabbits and such.  But by using handy government and organizational data, we can get at some numbers that might satisfy.

First, let’s tackle the easy part of the question: how many humans are there in the US?  By going to, we see in the “quick facts” section that the 2012 population estimate (the most recent available) is 313,914,040.   

To get at the animal figures, there are a few different resources one could consult.  Departments of Natural Resources within each state track wildlife population data, for example, and often make that information available to the public.  In addition, there are resources such as the Global Population Dynamics Database ( which provides species-level population datasets.   

For those interested in this type of research, there are several different methods by which animal species populations are measured.  A quick search in Library OneSearch using the keywords “animal population estimate” provides many different resources illustrating how some of the experts do this.

The Librarian exists to help you help yourself, normally providing seekers with the resources to find the answers themselves, rather than just giving them the answer.  

So if you came to the research help desk with this query, after some clarifying questions you would leave with a list of data sources and be equipped to answer this to the best of your ability.  Resources that would allow you to answer this question have population data broken down by species, so you could go to each of them, add up all the numbers, and get yourself the answer to this question.

The Librarian, unfortunately, has neither the time nor the column space for such a response.  We can, however, quickly answer a simplified version of this query: let’s see how many pet dogs there are per humans in the United States.  

We already have the human count from the Census, as illustrated above, now let’s tackle the number of dogs in the United States.  Turning to the most recent Statistical Abstract of the United States, available from the Library’s database list, we will find a table of household pet ownership.

 In 2011, the most recent year for which there are statistics, there were 69, 900, 000 pet dogs.  So the ratio of pet dogs to humans in the US is around 69,000,000 to 313,914,040.  Since The Librarian is not a mathematician, it is also up to you to make those numbers into a prettier ratio.  Let it never be said that The Librarian is not good at delegating.


Until next time, remember that we are always available to answer your questions via our Ask-a-Librarian service!  Send me your hardest questions here: