Replace_na with map function

Question

penguins %>% map(~replace_na(list(.=0)))

Why the code above didnt work to replace na in the dataset penguins?

The result is below

# A tibble: 8 x 1
      .
  <dbl>
1     0
2     0
3     0
4     0
5     0
6     0
7     0
8     0