Last year,
I had the immense privilege of walking East Anglia's coastline, 300 miles from the marshes and mudflats of Essex round to the endless sandy beaches of North Norfolk. By far my favourite wildlife encounters on this walk were those with seals. When walking along countless estuaries, I was regarded suspiciously by these furry ocean sentinels; whilst I was having breakfast on the beach at Horsey Gap, I noticed some inquisitive, furry faces popping out of the water to join me. These experiences sparked a deeper fascination in me for these exquisite, curious creatures.
Two seal species of the 18 worldwide make the UK their home: grey seals and harbour seals. Grey seals are easily identified by their elongated snouts, whilst harbour seals tend to be uniformly patterned with grey dots across their whole bodies.
Grey seal by Jackie Dent
Seals actually constitute a larger group of animals known as pinnipeds, which are formed of true seals (such as our grey and harbour seals), fur seals or sea lions, and walruses. All of the pinnipeds are intelligent creatures with highly evolved cognition, living in complicated social structures. Whilst the large colonies of seals you may see on beaches in the winter may look like chaos, they are actually organised social hierarchies, typically ruled by males who compete with each other for dominance and mating opportunities. Though relatively little is known about the social lives of seals, since they spend so much time in the water, it is known that they sometimes form 'cliques'. Much the same as school students may have defined friendship groups, certain individuals in a colony will hunt, sleep and play together.
One aspect of seals that is not so well known is that they are actually secondarily aquatic, meaning that they evolved from land animals (who initially radiated from water-dwelling fish and amphibians) and returned to the water, losing their land legs. Seals' closest living relatives are bears and mustelids (a group comprising animals such as otters and weasels), though there is still a debate raging as to which animal seals actually descend from.
Of course, a return to aquatic life meant that seals had to evolve (or re-evolve?) particular adaptations. They are actually fantastic deep divers: grey seals are able to hold their breath for over 20 minutes and have been known to dive 400 metres below the waves, whilst harbour seals can breath-hold for half an hour. No human diving to these depths would be able to withstand the immense pressure from the water column above them. Seals, however, have the incredible ability to collapse their lungs, mitigating the problem of too much dissolved nitrogen in the blood - commonly known as the bends in humans. Furthermore, to maximise efficiency of oxygen use, seals lower their metabolism when diving by up to 25% and have increased concentrations of myoglobin, an oxygen storage pigment, in their skeletal muscles to make up for their lack of inflated lungs.
Harbour seal by Elizabeth Dack
Sadly, with fish stocks increasingly depleted, these abilities to forage further afield for food are becoming ever more important. Warming seas, ocean acidification and plastic pollution are all altering marine ecosystems and threatening seals, as well as other marine creatures. Though the IUCN categorises grey and harbour seals as 'Least Concern', incidents where seals are trapped in fishing nets and other debris are becoming increasingly common.
Seals are vital to ocean ecosystems: they maintain the delicate balance of marine food webs by keeping populations of fish, squid and crustaceans at healthy levels, and providing food for larger marine predators such as sharks and orcas, which can sometimes be seen off British coastlines. Moreover, they are fantastic indicators of ocean health for marine scientists, since healthy seal populations signal sufficient fish populations, which in turn show that plankton and other algae populations are surviving.
The summer months are a great time for seals to bask in the sun on sandbanks and beaches around North Norfolk. However, there are a few things we can do to ensure this continues to be the case. Regular beach cleans, coupled with reduced consumption of plastic products, lessen the chances of seals getting caught up in debris. Reducing the amount of seafood in your diet is also important, as it relieves pressure on our oceans, allowing ecosystems to recover and re-equilibrate, as well as decreasing the amount of plastic pollution entering our seas from the fishing industry.
For me, seals, with their insatiable curiosity and enthusiasm for life, are the very embodiment of my passion for nature and the outdoors. It is through research, awareness and education that we can continue to ensure our oceans remain viable habitats for them and the other marine life we are privileged to share our waters with.
Katy Ellis grew up in East Anglia and is now studying Conservation Biology & Ecology at Exeter University. Passionate about adventure and science communication, she wants to encourage more people to get outdoors through her love for wildlife.
Header image: Grey seal by Elizabeth Dack