As it gets later into the breeding season here on the Isle of May, more and more of the grey seal mothers are weaning their pups and returning to sea to fish. Grey seals, like most species of true seals (called ‘phocids‘, including all earless seals), have one of the shortest dependant periods (the time the infant has to stay with the mother to survive) of all mammals, just 18 days. After that, mothers leave the colony and it’s up to the pups to look after themselves. Left to their own devices, newly weaned pups (called ‘weaners‘) soon find their way out of the colony or into nooks and crannies out of the way of the adult seals where they can rest and play, moulting their white baby fur (called lanugo) so they are ready to go to sea for the first time.
Moulting pups are usually much larger than when they were born despite only being 18 days old. Grey seal mothers produce milk with such a high fat content that pups can put on over 1.5kg a day in blubber tissue. Pups that are born at just over 10kg can therefore easily reach over 40kg in mass at weaning, and for seal pups the fatter they are at weaning the better as it means they are more likely to survive their first year of life. During their first year, a weaner’s body composition will dramatically change and they will go from the fat, round shape like in the above photo to a leaner look, like the yearling in the picture below. As a juvenile, a grey seal’s body composition is only about 12% fat of its total mass, a huge difference to the 45% fat individuals can have as weaners. These big changes in body composition are completely natural for the seals, but it means that it is vital for their fat tissue to function correctly both when they are rapidly generating blubber or mobilising it when they don’t have any food. That’s why the PHATS team are investigating whether the high persistent organic pollutant (POPs) burden that all marine mammals have in their blubber tissue is disrupting the seal’s ability to generate and utilise their fat reserves.
We now have 12 study weaners this year, all named after the phonetic alphabet as their identifying code in our project is a single letter. The largest of our pups is Lima, a male weighing 54kg! I introduced you to Charlie in the last blog when she had just weaned from her mother and still had lots of lanugo covering her body, she’s changed a lot in the last week! She’s moulted completely now and has really pale fur with subtle spots.
The other weaners in our study vary from pups that are almost completely covered in lanugo to fully moulted, and its interesting seeing the different patterns the weaners have hiding under their white baby fur. Here are some more introductions to our new study weaners, you can see Foxtrot (female) and Golf (male) in the photo at the top of the blog, and below are pictures of Alpha (male), the oldest pup in our study, and Kilo (male) snuggled up together and Delta (male) playing around with his flippers.
MEANWHILE away from the seals, we were all very keen to see the super moon, unfortunately the weather on the island did not co-operate and we didn’t get to see it in it’s full glory. We did all manage to see it before the sun rose the following morning and the next night, which was still very impressive!
Even though we didn’t get to see the super moon properly, we still felt it’s impact as we had huge tides on the island, and all the seals near the coast found the ocean encroaching where it doesn’t normally reach! The resulted in lots of seal pups getting swimming lessons with worried mothers in tow, and even some underwater nursing attempts.
Sadly it’s getting to the time in the season where some of the team have to think about leaving the island, including our team leader Dr Kimberley Bennett who has to go back to the Abertay University to continue teaching. It’s likely Holly and I will stay on the island until mid December to complete our work on the weaners, so we’ll be getting to know them very well in the coming weeks!
It’s now a very busy time in the breeding season and the island is coverd in grey seals of all ages, from newborns to females over 30 years old. The first weaners (pups who’s mothers have weaned them by going back to sea to eat fish, typically at about 18 days after birth) are starting to appear at the edges of the colony, without their mothers to protect them from aggressive adult seals the weaners quickly retreat to the peripheries of the colony. Even with so many seal pups of different ages around, it is still possible to tell approximately how old a seal pup is just by looking at it. It’s not always easy, but knowing the ages of the seal pups on the island is really important information for the various scientific projects studying the seals. For behaviour and physiology projects, it is crucial to know the developmental stage of a pup you are studying. For population dynamics research (which keeps track of the abundance of speices and detects changes in the numbers of individuals around our coast) knowing how long seal pups are present on a colony helps scientists accurately run models estimating pup production, an important variable in the model representing seal population changes around Scotland.
So how do you tell how old a pup is just by looking at it? Here is a crash course! Pups are divided into stages based on their appearence and the stages correspond to approximate ages (described here and drawn here). There are five stages in all, covering newborns to pups that have weaned and are independant from their mothers.
These pups are the youngest on the colony, and this stage covers pups that are newborn up until about day 5 of life. Things to look out for include a pink, squishy umbilical cord from the pup’s stomach and pronounced shoulders protruding from the pup’s back as they are quite skinny when they are born. The back slopes distinctly away from the shoulders down towards the tail, and sometimes they have dried blood from birth in their fur.
These pups are between 6 and 9 days old. Their umbilical chord has dried up and if it is still present, it looks withered and black. The pup will have increased it’s blubber layer just under the skin from drinking fat rich milk from it’s mother, so you won’t be able to see the shoulder blades easily any more. The back of the pup will still have a slight slope from the shoulders towards the tail, and there will still be a dip at the neck of the pup.
Pups within this stage are between 10 and 16 days old and are substantially fatter than the previous two stages. The back of these pups is almost flat because of how much blubber is covering the lower abdomen, and these pups start to look a little like barrels. The dip at the neck will have gone, but the pup will still be entirely covered in white pup fur called lanugo.
These pups can be very distinctive because it is defined by the pup losing (moulting) it’s white fur. As soon as a pup starts to moult the white lanugo, it becomes as stage 4 pup. The pups usually start to moult around their faces and flippers first, then the rest of their body follows over a few days. If the pup rubs against rocks or other seals then the white fur can come out in large patches at one time, revealing the adult fur underneath which is often patterned with spots. These pups are between 17 to 24 days old. At day 18, mothers typically wean their pups so you can see ‘weaners’ with half moulted white coats around the edges of the colony.
This is the last stage, and includes any pup that is more than 25 days old. These ‘weaners’ have no lanugo left on their body and can vary in colour from very pale, to spotty, to pure black. Weaners often stay on the breeding colony for several weeks after their mothers leave, which is called the post-weaning fast because they don’t have anything to eat while they remain on the colony without their mothers. To get food, they have to go to sea for the first time and learn to catch fish. This means that the amount of fat a pup puts on while it’s with its mother is very important for it’s survival; the fatter a pup is, the more blubber it has to burn for energy and the more time it has at sea to learn to catch fish before it starves. We still don’t really know why pups stay on the colony after weaning for so long as they often lose several kg of blubber during the post-weaning fast.
Being able to tell the age of pups is very important for the PHATS team as we are only interested in pups that are very close to weaning or have weaned from their mothers already (read our blog here for more details about why we sample the seals at these particular times). We have just identified our first study weaner, who is a stage 4 pup that has been dubbed ‘Charlie’ from the phonetic alphabet as her study code is ‘C’. We will be keeping an eye on her for the next two weeks during her post-weaning fast, so stay tuned for updates about her in the coming weeks!
In the tissue culture lab on the Isle of May we have received several samples from pups that are about to wean from their mothers and have been successful in keeping the cells alive for the PCB and hormone exposure experiments we are carrying out. To make sure that the cells are alive during the experiments, we sent some of our tissue back to the PHATS laboratory at Abertay University back on mainland Scotland. To do this, Dr James Turton extracted RNA (ribonucleic acid) from the fat tissue in our experiments and determined it’s integrity by putting it on a gel and applying an electrical current to separate out the different sized molecules in the RNA (know as gel electrophoresis). RNA is a vital component of all living cells, it is how DNA (Deoxyribonucleic acid) in the nucleus of cells transfers information to other parts of the cell so it can function normally. If the fat cells died during the experiment, the RNA would degrade and would not show up on the gel. Thankfully our cells were all alive and showed clear white bands of intact RNA on the gel after the test, confirming the RNA has good integrity and the cell in our experiment were alive. Hooray!
The other research on the island is also progressing well, Dr Sean Twiss from Durham University has been working in collaboration with Dr Patrick Pomeroy from the Sea Mammal Reseach Unit at the University of St Andrews to trial UAVs (unmanned aerial vehicles) for use in seal research. As they fly high over the colony they have the potential to be able to see areas of the island that we otherwise could not study, however the high winds that often blow over the Isle of May can make flying the UAVs difficult! Read more about Dr Twiss’ research on his blog about seal behaviour here.
MEANWHILE away from the seals, the epic cooking and baking continues! I baked batches of fresh bread rolls for a monster hand-made burger night when it was my turn to cook for the masses. Dr Twiss engineered an incredible sushi evening for dinner over the weekend, almost too pretty to eat! Last night we had a stunning roast leg of lamb, which PHATS team member Holly was in charge of, so good.
Ouside of the kitchen I’ve been amusing myself by working on my sketching skills, doodling various birds that I’ve seen on the island in my sketchpad between all the lab work. Hopefully by next weekend I’ll have a whole menagerie in my book!
For the PHATS team, our project work within the field season is officially starting today. One of the study mothers has now produced a large fat pup who is only one day away from weaning, so last night it was time for research assistant Holly, team leader Dr Kimberley Bennett and myself to get our tissue culture lab ready for the arrival of our first sample. When a blubber sample is taken from a seal for our work we use it in as many ways as possible to get the most information out of the tissue. We run some of the blubber to detect persistent organic pollutants (POPs) contamination in the pup, which is what I was doing over the summer in Belgium with our samples from 2015 (read about that here). The rest of the blubber will be kept warm and well fed with media solutions containing sugars, salts, proteins and fatty acids so that the cells within the tissue stay alive. We can then expose these blubber cells to different experimental treatments of POPs (like polychlorinated biphenyls, PCBs) or hormones that are meant to regulate fat tissue function to explore how hormones control fat mobilisation and how POPs interfere with this process. Tissue culture works involves a lot of lab equpiment that is tricky to ship out to remote research sites, but we have managed to find a small CO2 incubator and UV hood which we can transport out by boat to the island. With a lot of ethanol and lab diligence, we can create sterile conditions for culturing cells out here for the PHATS project, and we’ll spend the next 6 weeks keeping the tissue culture lab running here.
Around the island all the other scietific research projects on both the seals and the birds continue as the season progresses. There are many other projects that are happening at the same time as ours on both the seals and the birds here on the island. Over the last week, Callan Duck from the Sea Mammal Research Unit has conducted an aerial survey of the entire Isle of May colony by plane to perform the annual count of grey seals on the island. Callan will fly over grey seal haul outs all across Scotland throughout the breeding season to monitor the size of seal populations around the country. The bird researchers from the Centre for Ecology and Hydrology are also doing the last mist netting and trapping to catch and ring birds on the island before their research station at the Low Light closes for the winter. They have been kind enough to show us many of the interesting birds they have ringed over the last week, inlcuding waxwings, fieldfares and a long eared owl!
MEANWHILE We’ve had two birthdays in the last week so the PHATS team has been baking! I’ve made birthday cake, Holly helped make 60 profiteroles by hand and Kimberley made an epic beef and ale pie for dinner last night. The team leader here on the island also treats us to pancakes every sunday, so we had a lovely morning yesterday enjoying the biggest stack of pancakes I have ever seen.
We now have a Twitter feed! Please follow us @KJRScience for more photos, news and #IslandLife shenanigans!
The first week of our stay on the Isle of May grey seal breeding colony has flown by, and the number of mother – pup pairs is growing daily. The PHATS team from Abertay University and the Sea Mammal Research Unit, University of St Andrews is still waiting for our first sampling opportunity before we can start work, looking at persistant organic pollutants(POPs) and how they affect fat tissue function in seals. We will get the chance to start our sample collection in about a week, when the pups are almost ready to wean from their mothers and are large and fat (see the previous blog for more details about our sampling regime). While we wait both Holly and I are helping survey the colony regularly by doing observations of the seals arriving and looking to see if any seals are study individuals. Study individuals are females that have been included in the Isle of May grey seal research project for many years, and they usually have small flipper tags to help us identify them. Female grey seals typically come back to the same colony to give birth, and as they have spotty patterns on their fur that stay the same throughout their lives, we can identify the same females year after year and build up long term datasets of what happened to them across many years.
All the other research projects on the Isle of May are in full swing, as they are interested in the seals from when the pups are born right through to weaning. For example, Dr Sean Twiss is leading a team here from Durham University studying the maternal behaviour of grey seals and how it can be linked to physiological metrics like heart rate data from novel, external loggers they designed and built themselves (read more about their research here). There is always plenty going on to observe in the colony, never a dull moment! Here are a few of the behaviours you can see currently on the Isle of May breeding colony:
Grey seal births are extremely rapid and can be tricky to see. After the birth, mothers will sniff their pup and bond with it so they can stay together for the coming weeks on the busy colony. Newborn pups are pretty easy to spot as the mothers can be quite red from the blood lost during delivery and sea gulls come to scavenge the placenta to eat. Seal mothers do not always react well to this, and can spend lots of time chasing gulls away from themselves, their pup and the placenta. My PhD work was primarily on maternal behaviour and how mother-pup bonds form, and I always love watching births if I can spot one.
Grey seal mothers only spend about 18 days with their pups before weaning them and going back to sea. In those 18 days it is vital for the pup to drink as much fat rich milk from the mother as possible, the larger a pup is at weaning the more likely it is to survive its first year of life. Grey seal milk is 60% fat so pups can put on weight very quickly, pups born at 18kg can easily reach more than 50kg in just over two weeks! Nursing bouts take about five minutes and happen approximately ever four hours throughout the day and night.
Defending the pup from other seals and gulls
A grey seal mother will aggressively defend her pup from anything that approaches too closely. Other female seals will attack any pup that is not their own and males will not tolerate pups in their personal space either. Without their mothers to defend them, pups soon become covered in bites from other adults. Sea gulls can also seriously injure, and in some cases kill, grey seal pups by pecking at their eyes and fresh umbilical. Mothers therefore do not tolerate gulls coming to close and will aggressively chase them away.
Male dominance fights
As the breeding season progresses, more male grey seals arrive on the colony to try and hold a position among the females, so that they can try to mate with them once the pups are raised. Males will threaten each other with hisses and open mouth threat displays, but many confrontations do not result in fights as these are dangerous and tiring for both parties. Sometimes however, neither male will back down and the two will fight brutal battles for dominance, biting and shaking each other’s necks and heads.
MEANWHILE away from the seals, the team on the Isle of May are enjoying island life as much as possible. The sunrises here are stunning and there are lots of amazing birds flying around to watch out for, the short eared owls are a particular favourite currently. Half of the team indulged in a rare TV night to join the rest of the nation in watching the Great British
Bake Off final, and as that put me in a baking mood I made some coffee and walnut cupcakes for everyone. We were joined yesterday by the leader of the PHATS team, Dr Kimberley Bennett fresh from teaching at Abertay University and she brought some fresh food supplies, even more lab gear and halloween goodies! Cue some epic pumpkin carving by Holly and fellow research assistant Izzy, now to put them somewhere high so the mice don’t attack them in the night!