Breed Census

There are several different ways to look at population size.  One is to do a head count: how many dogs are there in the breed?  The simple answer to this is, no one knows how many English Shepherds there are – but, based on what we can see from litter registrations, participation in online forums, etc, the total population (“N”) is likely over 10,000.

Number of Sires and Dams

When we study the health and genetics of a breed, however, we need more than a simple head count.  We also need to know the number of breeding dogs – and, more specifically, the number of males and females contributing to the gene pool.  The number of breeding dogs and the ratio of males to females can be used to estimate an “effective population size” (Ne).  When this information is taken into account, the breed’s effective population size appears to be roughly 800. Chart Trend in English Shepherd Population

Data source: ESCR There has been a steady upward trend over the past 15 years, with numbers of sires, dams, litters and “effective population size” for the current generation roughly triple what they were 15 years ago. This is important information for conservation breeders but there is one additional piece of information needed to really understand the size of the breed’s gene pool: we need to know how closely related dogs in the present generation are to one another.  The size of population’s gene pool depends on how many different, unrelated, dogs contribute to it.  To get a handle on this last key piece of information, the relationships between dogs within the breed, we can look at pedigree records and genetic testing.

Genetic Testing and Population Size

Over the past 5 years, more than 1000 English Shepherds have undergone genetic testing by Embark.  Annual reports allow us to monitor the level of inbreeding.  Changes in the level of inbreeding within the population over time can be used to refine estimates of “effective population size”. The data available for English Shepherds tested by Embark suggests that the average level of inbreeding in the breed has increased by 1% over the past 3+ years.  While 1% may seem like a small number, a 1% increase in COI in just one generation suggests an effective population size of only 50.

Inbreeding Trend English Shepherds

Data source: Embark The rate of inbreeding tends to increase very rapidly when populations drop below 50.  This has important implications for breed health:

  • An effective population size that is less than 50 is considered to be at high risk of detrimental effects of inbreeding.
  • Inbreeding may increase risk for genetic disorders.  Inbred populations are also at risk of inbreeding depression, which is reflected in an overall decrease in general fitness, or general health, and reduced litter sizes and fertility.[1]

Are There Too Many English Shepherds?

So, circling back to where we started: are there really too many dogs, too many breeders, too many litters?  Or, is the rapid increase in census numbers only telling us one side of the story?  Please come join us on Facebook and share your experience, thoughts, and questions about this and other important topics!