To find out how many of the pets in the store are dogs, you can calculate 40% of the total number of pets.
\[ \text{Number of dogs} = 0.40 \times \text{Total number of pets} \]
Given that there are 40 pets in the store:
\[ \text{Number of dogs} = 0.40 \times 40 = 16 \]
Therefore, there are 16 dogs in the pet store.