Does Jack Russell terriers female dogs have periods?

Dogs, no matter the breed usually have their first heat cycle sometime between 7 months to one year of age, after that they usually have two heat cycles a year. Just as with a humans menstrual cycle, you can't always accurately predict when it will occur.

A female dog gets the most health benefits from being spayed before the onset of her first heat cycle. There are many low cost and reduced cost spay and neuter clinics all over the country. Contact your local animal shelter or Humane Society to find a clinic near to where you live, if you affording the surgery is a concern.