By Katie Gadson
If you ever visit the Cornish and Devon countryside you will never need to go abroad again. My own family holidays have always been best when we are out exploring the headlands or the beaches, even in the British weather, rather than getting sunburned by the pool. It’s a place where a picture may tell a thousand words but never capture the true wild beauty of the vast cliffs. It’s a place where you could sit for hours watching the sea up in the purple heather and the wind and never get bored, only hungry for a pasty if you’re willing to fend off the seagulls! This article is a brief window into the lives of some of the creatures I encountered in my travels this year and it begins with a pesky seagull.
This is Colin, a seagull I befriended who was hanging around trying to nab my delicious chips. He is a stereotypical herring gull and only a young one as he still hasn’t got all his adult feathers. Although we would all have come across a herring gull before, unfortunately populations at coastal sites have halved in the last 25 years. The damage we have caused to the seas with pollution and decreased fish stocks have caused these birds to move into urban areas and while this might pose a danger to our chips, it’s important to live alongside our wildlife instead of regarding them as pests. In 50 years, we have lost 40 million UK birds so it’s important to restore and protect their habitats.
The most curious thing about gulls is the red splotch on their yellow beaks. Research has shown this is used for social signalling and for feeding their chicks. If the chick pecks at the spot the parent will feed it and in fact the chick will beg at anything that’s yellow with a red spot on it. Herring gulls can also drink salt water because they have a gland on top of their skull which removes the salt and excretes it out through the nose to drip off of the beak. Another feeding behaviour of adult gulls is to tap with their feet rapidly on the ground so that worms come to the surface (this is a worm escape mechanism as the vibrations mimic an approaching mole). Feeding the seagulls not only encourages them to attack people with food (my sister and her pasty or my mum with her rum and raisin) but it’s also bad because females with a diet higher in terrestrial foods and lower in marine foods produce smaller eggs. Some research into seagull food snatching suggests that only 26% of the gulls actually touched the food but they approached more slowly if the person with the food made direct eye contact with them. I found this interesting as I was looking and talking to Colin and he would pretend like he wasn’t interested until I looked away for a second and then he would try and sneak up behind me. Luckily he never managed to deprive me of my much-needed carbs.
Fun fact about Herring gulls: They can see ultraviolet light! There is an rspb approved gel which appears orange to humans but like flames to seagulls, deterring the seagulls. It's made of food grade natural oils and may only cause temporary discomfort to a landing bird. It’s therefore better than spikes, netting and electric shocks when trying to keep the seagulls off of a building.
Another very important and rare bird to see in Cornwall is the Cornish Chough. It
is also known as digger because it has a curved bill which it uses to search the
soil for bugs. It completely disappeared in Cornwall when farming practises
changed with the last breeding pair spotted in 1967. Farmers moved their grazing animals inland away from the coast where they were easier to manage which led to the land becoming more overgrown so that choughs no longer had access to the soil and couldn’t find the insects which made up their diet. Also, young choughs could find insects in animal dung which was easier for them than digging at the ground. In the nineteenth century they were also hunted as pests and egg collectors also contributed to their decline. However, by returning some grazing animals to the coastline choughs naturally reintroduced themselves in 2001 and while the numbers are still low, they have stabilised which is good news! Choughs like to live on the coast because there are many suitable places on the cliff faces and in caves to build their nests and shelter away from predators.
Fun fact about choughs: They are depicted on Cornwall’s coat of arms and according to legend king Arthur transformed into a chough upon his death.
One evening my family and I walked down to the harbour in Torquay in Devon. If we hadn’t been lucky before, there was no doubt that we were now because we saw jellyfish for the first and only time in two weeks, a seal which had come into the harbour and a dolphin which kept swimming towards the beach before going back out to sea. At first, when I spotted its fin, I thought it was a shark which my sister found hilarious. We also visited greenway, Agatha Christie’s summer home on the Dartmouth estuary where we saw Oysters.
Jellyfish are one of the earliest lifeforms to originate in the oceans and have been around for about 500 million years since the dinosaurs. The compass jellyfish eats small fish, marine invertebrates, crabs and other jellyfish. They use their four frilly arms to move food towards the mouth. They have 24 long tentacles which have sting cells that fire when touched (when you touch a sting cell it opens and water rushes in. This causes a needle-like stinger to shoot out and release a toxin into your body this happens in about 3 milliseconds). If you get stung, the jellyfish leaves the tentacle behind and it can carry on stinging you, so the tentacle should be removed. Don’t worry there’s no need to pee on it because it will do absolutely nothing to help. If you have vinegar you could put some of this on.
Even if the jellyfish is dead, when the tentacles are wet, they can still sting. There are eight sets of three tentacles with sensory organs between each one which detects light and smells. This is how they tell their own orientation in the water. Jellyfish move with the currents but they also move a lot themselves, it’s just mainly vertical. They also have sensory pits which detect chemical cues which may be how they communicate but since they are solitary this is yet to be thoroughly studied.
Unfortunately, they are out competing other fish and whilst their numbers increase, the fish stocks decrease. They are also robust when it comes to climate change and can grow and shrink depending on the levels of nutrients they receive.
Fun facts about compass jellyfish: They start their lives as males and when they get big enough they become females and start producing egg cells. They are made up of 95% water! They don’t have blood, a brain, or a heart.
Grey seals are found all around the UK and they represent 40% of the world’s seal population (95% of the European population). They can live for 30 years and it takes the pups 3-6 years to grow to maturity. The pups stay on land until they have lost their white coats and trebled their body weight which takes about a month (the mother’s milk is over 50% fat and eventually the mother will lose up to a quarter of her own weight) unlike common seals whose pups can swim only hours after being born!
They are prey for sharks and killer whales and eagles sometimes hunt the pups as well. Some more recent studies have shown, rather darkly, that some males will also kill and eat pups of their own species as they can stay in their territory which will improve their reproductive success!
To communicate they use their voices but they will also clap underwater to scare away predators and to find a potential mate. This may be affected by the noise pollution created by humans. They have large eyes which help them see in dark deep water but their hearing is most important when hunting.
When underwater seals slow their heart rate (from about 70 bpm to 7 bpm) to conserve oxygen since they can’t breathe underwater. They have a lot more haemoglobin compared to humans so that oxygen can still reach every cell in their body. Oxygen is also stored in myoglobin, another storage pigment and seals have a large blood volume. This is because oxygen can’t be stored in the lungs during deep dives due to high pressures. Additionally, if the lungs were full of oxygen this would create unwanted buoyancy. Amazingly the kidneys temporarily stop functioning during a dive to conserve energy. A thick layer of blubber helps keep them warm and doesn’t collapse under the pressure of the deep sea. This allows them to stay underwater for as long as thirty minutes.
Fun Fact about grey seals: Their latin name Halichoerus grypus means hook-nosed sea pig.
Pods of common dolphins are often seen containing hundreds of dolphins who, genetic studies have shown, are not closely related to one another. In fact, unlike many other dolphin species, common dolphins don’t have a matriarchal society and its unknown whether they spend their whole lives in their pods. This is different to long term male alliances found in bottlenose dolphins. They do however have a home range, as dolphins they are more closely related to are still found close by. There are over six million common dolphins in the world’s oceans and so they are listed as of least concern on the IUCN red list. The main human threat to common dolphins is bycatch and it’s estimated that if the ban on fishing was moved from 300m to 250m and if there were some seasonal closures based on when there are the most dolphins in the area, 78% of the dolphins wouldn’t have been caught.
Common dolphins have a signature whistle similar to a name which takes a calf a year to learn. It’s used if a dolphin gets separated from the group or if a dolphin is trying to locate another. Captive bottlenose dolphins still emit these signature whistles even when it's not possible that they have been separated, so there’s reason to believe that more information than identity and location is transmitted. This is a significant finding because most animals have inherited sounds and not learned sounds but the dolphins not only learn their own whistles but they also learn the whistles of others in the group. They caN remember a pod member’s whistle 20 years after last hearing it.
Dolphins can fill their ten litre lungs in a third of a second. They have a pair of phonic lips near the top of the skull for each nostril and they pass air over these independently so that they can produce clicks and whistles at the same time. A fat filled structure called the melon focuses the sound as it’s used in echolocation to find food. Fat pads in the lower jaw receive the information and pass it to the inner ear. They can detect a shoal from over 80m away. The dolphins brain takes up 20% of its metabolic energy so a high calorie diet is important. They mainly eat fish and will work together to herd their prey into a ball. When hunting they can swim at around 30mph. They can swim as deep as 200m. Dolphins sleep with half their brain awake and one eye open. This is because they have a voluntary respiratory system and would otherwise suffocate. The active side watches for predators and other animals and signals to the dolphin when it needs to rise to the surface for air. It also keeps control of the blowhole (a flap of skin that opens and closes voluntarily) so that it doesn’t allow water to come in. When a calf is born they haven’t built up enough blubber to float so they ride in the stream of water created by the movement of the mother. This means that the mother can’t stop swimming for the first few weeks of the calf’s life or it will sink and suffocate so the mother sleeps whilst swimming.
One test for intelligence is the mirror test and dolphins have shown to be one of the only known species to recognise themselves in the mirror, showing a high level of self-awareness. They actually recognise themselves earlier in life than humans, about seven months compared to 15 or 18. They have also demonstrated behaviour that suggests complex emotions and have spindle neurons in their brains which are responsible for decision making, emotions and the assessment of social interactions. They play together, learn from each other, use tools such as sea sponges when foraging, and are even capable of understanding human speech, showing that they are highly intelligent animals.
Fun Fact about common dolphins: The skeletal structure is similar to human hands and they have vertical spines, a characteristic of animals who can run on land. The oldest relatives that we can link with dolphins were actually terrestrial with hooves and ventured into shallow water to find food.
Oysters are filter feeders, which means they use hair like protrusions called cilia to waft water and food over their gills where the food is trapped in mucus and transported to the mouth. This is significant because it takes algae, organic matter and excess nutrients out of the water and improves water quality and increases oxygen levels for other marine life. They can filter 190 litres of water per day. However, toxins can stay in the tissues so if they are being used for food they should be purified first.
Pacific Oysters are not a native species and are invasive. In Devon and
Cornwall there has been an explosion of the population in estuaries leading to them needing to be culled as they are out competing other marine life including native common oysters. They take only a couple of years to reach maturity and each year, they can produce up to 200 million larvae. The water used to be too cold for them to reproduce, but due to global warming, the sea is now at the optimum temperature for them to grow. When the larvae find a suitable habitat they secrete a cement from a gland in their foot which attaches them usually to rock but sometimes on other oysters to form reefs.
Pearls are formed when an irritant gets into the shell such as a parasite and are encased in nacre (mother of pearl). Though a lot of oysters make pearls, these don’t look like commercial pearls which come from pearl oysters. These are a different kind of bivalve that are not closely related with true oysters. They have a three chambered heart and colourless blood; they also don’t have a brain. They start male but as they grow they
become female. Adductor muscle which is the main body of the oyster keeps the shell closed whilst the hinge muscle can open it. They have bundles of neurons and two pairs of nerve chords to control their muscles and organs but no central nervous system so are unlikely to feel pain.
Fun Facts about oysters: Oysters have eye spots that detect light and dark which helps them to protect themselves against predators, as they can close their shells. They can also clap their shells together which pushes all the water and waste products from its body, in effect going for a poo!
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