Biology
A juvenile harbour seal
Harbour seals are usually sexually mature after the first five years of life and can live up to 35 years of age.
In UK-waters, harbour seals can sometimes be found alongside the larger grey seal (Halichoerus grypus). Both species are vulnerable to viral distemper caused by PDV (Phocine Distemper Virus) but mortalities in the grey seal are not as pronounced.