
The Society's membership base is global. Although most are based in the British Isles, there are significant numbers in Europe (especially Germany and Norway), Australia, Canada, the USA, with smaller numbers in Asia and Africa.
Membership is open to anyone with an interest in furthering the objectives of the Society.
Full members are mostly professional biologists working in universities, government agencies, research institutions and private companies.
Associate members include: students, who are mostly postgraduates working towards masters or doctoral degrees; and persons retired from full-time employment but interested and/or active in areas related to the Society's objectives.
Full members include persons who have made major contributions to the Society and its objectives, with recipients of the Beverton medal automatically becoming Honorary life members.
About half of the members of the Society live outside the British Isles, and there are members from all over the world. In 2005, the membership distribution was:
| United Kingdom & Republic of Ireland |
415 |
| Rest of Europe | 150 |
| Africa | 5 |
| Middle East | 6 |
| Australasia | 50 |
| North America | 78 |
| South and Central America | 15 |
| Far East | 19 |
| Indian subcontinent | 11 |