Grey seals (Halichoerus grypus) will mate during the pupping season (August-December in North Wales). Mating is triggered by hormone changes in both male and female seals. Once the nursing period has finished, the females will mate with a dominant male. Females (cows) reach maturity between 3-5 years and males (bulls) reach maturity between 4-6 years. However, older males which are around 10 years old will compete with other male seals for ‘beach power’. Males which have only just reached maturity will be outcompeted and may not mate that season. However, it is important to note that not all males will need to outcompete other males and less competitive males can still mate. This will depend on the size of the colony and other environmental factors.

I remember a photographer once telling me that at one point during a particular eventful morning, the shallows were red with the blood of fighting males! - Dawn Thomas

The mating process is loud and aggressive due to the increase in hormone levels and territorial nature of the males to claim dominance. Fighting can happen between the seals which can cause scaring. This can mean the hauling site can become a loud and busy environment which isn’t ideal for pups. It is important that the seals aren’t disturbed during this time to ensure mating isn’t disrupted. This could lead to a behavioural change and endanger the pups and seals. Disturbance is shown by increased alertness and movement on the haul out sites or retreating to water. Anyone going in the water which has an area with seals, should follow the local Marine Code for best practices (Conwy, Gwynedd, Ynys Môn).  

Pregnancy in grey seals is delayed. Called ‘embryonic diapause’, the fertilised egg will remain dormant which prevents development of the embryo. The delayed development is around 2-4 months. This ensures conditions are more favourable for the pup to have the best chance of survival. Additionally, it allows the mother to moult her fur and feed to restore her energy levels for the pregnancy.

If you are concerned about the welfare of a seal, you can call the following numbers for advice. British Divers Marine Life Rescue (01825 765546) 24 hours or RSPCA (0300 1234 999) 24 hours. It is important to never approach a seal or pup due to disturbance can led to the mother abandoning the seal pup. Additionally, when viewing seals always make sure you are being respectful and keeping noise levels to a minimum. A distance should always be maintained, and dogs should be always kept on leads.

- BLOG created by Molly Jones