Just like that, my time at the University of Liege has finished and I’m back at the Sea Mammal Research Unit in Scotland. I was successful in preparing all our grey seal blubber samples for analysis, and now we just need to wait for the results from the Gas Chromatography – Mass Spectrometry (GC-MS)
machines. We will hopefully get all our results by July, and in the meantime I will get back to the bichemical analysis of the samples from the tissue culture experiments on the Isle of May last year. My last few days in Liege flew by, a whirl of labwork, tasty Belgian fries and one last trip to Masion du Peket to enjoy their delicious drinks!
We’re not just focusing on labwork here on the PHATS team however. We’ve been working hard on analysing our data and are now ready to start getting our science out there! We’ll hopefully be attending conferences this year to present our findings, and if you are interested in our work do come and find us at the below venues. I will also hopefully be presenting some of my work on the hormone oxytocin and it’s affects on bonding, social and maternal behaviour in seals. While the blog will be on hiatus until we return to the field in October, we will update it when we attend or present at conferences, or if we publish any papers on our work so watch this space!
30th July – 4th August: Behaviour 2017 (ASAB summer meeting & 35th International Ethological Conference)
My last week at the University of Liege has arrived, and I’m working hard to ensure that all the PHATS team’s labwork is complete before I leave to return home. All of our samples are now ready for analysis that will let us detect PCB and PBDE levels in our Scottish grey seals. PCBs and PBDEs are two types of the many persistent organic pollutants (POPs) that are present in our environment. I am currently working on preparing our samples for another type of analysis that will enable us to detect a third kind, OCPs. As POPs in our environment, and PCBs in particular, are still currently in the news after the recent revelation of just how highly contaminated with PCBs some marine mammals are becoming, I thought I’d spend this blog introducing the three types of POP I work on and why they are so problematic.
PCBs, or polychlorinated biphenyls, are pollutants that are made up of two linked rings of carbon atoms with a varying number of hydrogen and chlorine atoms bound to the rings at different positions. There are many possible combinations of the number and locations of the hydrogen and chlorine atoms binding to the rings, and these give rise to the large variety of PCBs (called congeners) that exist. Approximately 130 different types of PCB are found in commercial products, and they can be divided into two groups (dioxin-like and non-dioxin-like) based on their structure and toxicity. PCB production was banned in the USA in 1979 and by the Stockholm convention (signed by over 150 countries worldwide) in 2001, however they persist in our environment due to their slow degradation rates. One of the main reasons PCBs were previously manufactured and used in industry was their inert properties; only incineration at high temperatures can safely destroy them. Previous uses of PCBs include in coolants and lubricating oils, paints and electric wire coatings.
PBDEs, or Polybrominated diphenyl ethers, are also made up of two carbon rings, but they have bromine bound to the rings rather than chlorine. The fewer the bromine atoms per molecule of PBDE, the more dangerous they are considered to be as congeners with between 1-5 bromine atoms bioaccumulate more effectively in living organisms. PBDEs are still being manufactured and widely used in many man-made products, the Stockholme convention which banned PCBs only restricted the production of some PBDEs. Some states in the USA have begun prohibiting their manufacture and use in the last decade however. PBDEs are flame retardant and are therefore commonly incorporated into electronics, plastics, fabrics and other building materials.
OCPs, or organochlorine pesticides, contain carbon, hydrogen and at least one bound chlorine atom but do not contain carbon ring structures like PCBs and PBDEs. There are many different types of OCP, however arguably the most well known is DDT (Dichlorodiphenyltrichloroethane) which was heavily used as a pesticide across the world to kill insects for both agricultural and disease control purposes. The famous book ‘Silent Spring’, written by Rachel Carson in the 1960s, is all about OCPs and the negative impact overuse of pesticides has on the environment. The production and use of some OCPs like DDT and heptachlor has been strictly limited by the Stockholme convention. Due to their efficiency at killing insects, their use is still permitted in some circumstances, such as the use of DDT to control mosquitoes that carry diseases like malaria.
POPs have been connected to a wide range of negative health impacts in both people and wildlife, and chronic exposure to any type of POP will cause problems for any organism. All POPs are carcinogenic (cancer causing) and are potent endocrine disruptors, interfering with growth and development, immune function and reproductive systems. There is growing evidence that POPs impact on obesity, leading them to be labelled as ‘obesogens’. The PHATS project I am part of is hoping to uncover some of the underlying physiological and genetic mechanisms that influence fat tissue function and determine how POPs can interfere with these processes. By studying a marine mammal species which has lots of fat and lots of bioaccumulated POPs, we can gain a better understanding of how these chemicals have such far reaching and devastating impacts on our health and the environment.
It’s been another busy week here in chemistry labs at the University of Liege. I’ve completed extracting all the PHATS team’s blubber samples for persistent organic pollutant (POP) analysis, and now am moving on to the purification part of the sample preparation process. I’ve only got two weeks left to get all the sample preparation completed, so hopefully all the lab work will go according to plan! The purification process isn’t too complicated but it does have lots of time consuming steps, from multiple standard spikes, to acid clean-up on columns, to concentrating the samples down via nitrogen evaporation. So it’s just a case of getting your head down and getting on with it all, as the sooner it’s done the sooner we’ll have some interesting results to look through.
The results of POP studies are frequently worrying as well as interesting. A good example of this happened last week, when the Scottish Marine Animal Stranding Scheme (SMASS) got some lab results back showing the PCB concentrations in one of the stranded whales they had examined last year, ‘Lulu’, one of Scotland’s few resident orca. She sadly had one of the highest ever recorded concentrations of PCBs in her body, and there are concerns that the other members of her pod will have similarly high levels. Another interesting (and sad) aspect of Lulu’s case is that she had never produced a calf, despite the fact she was about 20 years old and orca usually have their first calves at around 14 years of age. It is well known that POPs negatively impact on individual health, including fertility, therefore it is possible Lulu failed to reproduce due to her high pollutant burden. Even more concerning however, is what might have happened to Lulu’s high PCB concentrations if she had produced a calf.
Another major cause of patterns in POP concentrations in marine mammals is their position in the food chain (their trophic level) and the region they obtain their food from. Orca represent a fascinating opportunity to study these patterns as through-out the species, there are different populations that specialise in eating either fish or other marine mammals, or in other words different orca populations can occupy different tropic levels of a food chain. Groups that eat marine mammals, such as seals, sea lions and porpoises, typically have over double the concentrations of POPs in them than fish eating groups. This happens because the pollutants have become concentrated up the food chain due to bioaccumulation, where a predator eating lots of smaller prey gets all the pollutants in each individual it eats. A whale eating lots of seals to survive will accumulate all the pollutants all the seals were exposed to, and all the pollutants all the fish those seals ate too. Meanwhile a fish eating individual will ‘only’ accumulate the pollutants from the fish it eats. Additionally, individuals that hunt in highly industrialised areas have higher concentrations than those in ‘pristine’ areas, because the more POPs that are in a local area, the higher the concentrations in all the organisms from the bottom of the food chain to the top.
Studying patterns of POP concentrations in different types of individuals can therefore lead to a better understanding of how these persistent pollutants ‘move’ through organisms and can be transferred into later generations. It is not hard to see why POPs continue to be a problem for animal and human health, despite being banned decades ago.
Well my first week at the University of Liege working with CART has flown by, and I’ve been working on the blubber biopsies we collected from the grey seals last year on the Isle of May. All the lipids (fats) need to be extracted from the blubber tissue before we can move forward with the pollutant analysis, so all the samples must be carefully prepared and put through Accelerated Solvent Extraction (ASE). This process uses high pressure and temperature conditions plus chemicals called solvents (like hexane and acetone) to remove all the lipids from the sample in the cells. This process gives us a completely liquid solution of lipids and solvents at the end of it, and we can then evaporate the solvent to leave just the lipids from our sample. This step is important as it gives the lipid mass of our sample, and allows us to work out how many nanograms of pollutant per gram of lipid in our sample there is (ng/g) . While ASE of our samples is an important step in the lab work, there isn’t really much more to say about it so I’m going to use the rest of the blog this week to give a brief introduction to blubber tissue, a crucial part of the anatomy of all marine mammal species worldwide.
All marine mammals, from the largest whale to the smallest seal, have a layer of fat underneath their skin called blubber. This layer of fat is extremely important for the survival of marine mammals for two reasons:
It enables them to keep warm (thermoregulate) in freezing oceans.
It provides a store of energy for individuals to utilise when they are not feeding, which happens in many marine mammal species at various points throughout their lives due to breeding or moulting.
Fat tissue deposits in all animal species perform these same two functions, however other species frequently have additional ways to thermoregulate (such as fur in land mammals) or do not endure long periods of fasting repeatedly while migrating or breeding as many marine mammals do. The importance of this tissue has lead to substantial blubber thickness evolving in marine mammals, and a stratified structure throughout the depth of the tissue is present so that it can perform both functions at the same time. Typically, blubber tissue can be roughly divided into three sections as you go from the part closest to the skin (the outer blubber) to the part closest to the inside of the seal (the inner blubber). The inner blubber is the most metabolically active, and this is where lipids are mobilised to provide energy for an individual when it either cannot find food or is purposefully fasting. The mid blubber is the most variable in thickness across individual marine mammals, and in thin individuals can be completely absent. It is thought it acts as a more long term storage tissue, and that its thickness is influenced by seasonal food availability. The outer blubber is typically of stable thickness within a species regardless of the nutritional state of an individual, and is thought to be primarily for thermoregulation. Hence even starving individuals will always have some blubber tissue to keep them from freezing, as the outer blubber is not mobilised as an energetic resource.
Blubber is a fascinating tissue to study and several different approaches can be used to analyse it in many contexts, like this recent study by one of my friends, Joanna Kershaw, who measured the hormone cortisol in blubber from porpoises to validate it’s use as a biomarker of body condition. The PHATS project I work on uses both established techniques (investigating pollutant concentrations) and novel protocols (the explant approach for tissue culture experiments that our team leader pioneered in seals) to make the most of the blubber samples we collect from our study animals to explore the prevalence of persistent organic pollutants in the marine environment and it’s impact on energy balance in seals.
MEANWHILE I am settling back into Liege life quite happily outside of the lab. I am not staying in the university accomodation this year, and have a lovely little flat not far from the campus to retreat to. In my time away from the lab I’m trying to keep up with the usual paper and grant writting that all resarchers need to keep on top of, plus greatly enjoying bebing reunited with the amazing macaroons they make here! Seriously, why can’t they be this good in Scotland…
Welcome back to my corner of the internet and the PHATS blog! The first four months of 2017 have flown by as the team has headed back into their labs to analyse all the samples we collected over the winter on the Isle of May grey seal breeding colony (to read about our fieldwork adventures, see these blogs here). I was lucky enough to escape to perform a survey of the Isle of May in January, to see if there were any grey seals that were moulting early in the year. There were plenty of them as it turned out, which bodes well for the fieldwork we are planning next year to try and look at moulting seal physiology. The island already looks so different to how it was when the seals breed there in the winter, much greener and all the seabirds are starting to come back. The cliffs were lined with guillemots, razorbills and shags; some were even getting started on gathering nesting material. The puffins had not returned yet, they arrive later in the year closer to summer, but we did see a few on the water during the boat crossing to the island.
Inside the lab, I’ve been working on biochemical analysis of the cell culture media from all the blubber sample experiments last year (see here for more info) and am now two thirds through the samples we generated. By measuring the metabolic profiles of the various blubber culture experiments, we can see if the pollutant or hormone treatments had any impact on the blubber cells we collected from the seals. I’m also working on validating ELISAs (Enzyme-linked immunosorbent assays) to detect a variety of hormones in the blood samples we collected from the seals last year, so we can see if an individual’s hormone profiles are linked to their pollutant burden.
Using ELISAs on wild animal species like grey seals can be tricky, as they use antibodies as part of a binding process to detect the hormone you are interested in. These antibodies will have come from a specific species of mammal, usually rodent or domestic animal species that lots of scientists study, and the company making the ELISA kit will provide a list of species they know the kit works with. As a hormone’s protein structure is not always the same in different species of animals, the antibodies used in a widely available ELISA kit may not react properly with samples from unusual species that has never been tested with that kit before. Unfortunately seals often fall into the ‘unusual’ category, so we need to test the kits (validate them) before we use them to run lots of our samples, to make sure the results we are getting from the kits are accurate. There are several things to check when validating an ELISA, some of the most important are:
Test for linearity. By diluting some of your samples (e.g. to half the concentration, then a quarter, then an eighth etc) you can make a serial dilution series to run on the kit. You can then see whether the curve the dilution series produces is parallel to the standard curve, which is what the kit uses to determine hormone concentrations. If the curve is not parallel to the standard curve, then the hormone in your samples is not binding correctly to the kit components.
Test for recovery. By spiking a sample with a known quantity of the hormone you are interested in studying, you can tell how much the kit is detecting and how much is ‘lost’ during the analysis process.
Test for consistency across kits and within kits. Many studies have lots of samples and need to use more than one kit to analyse them all. You must make sure the results of one kit are comparable to the others (inter-assay coefficient of variance), and the easiest way to do this is to run the same sample on each kit you use. You can then calculate the coefficient of variance across all the kits you have run. It’s also important to check the kit’s internal consistency (intra-assay coefficient of variance) by running one sample multiple times on a plate and seeing how similar the results are, and by running all samples in duplicate on the kit.
Our seal blood samples are proving to be rather tricky currently, and we’re still working on which are the best kits to use to measure the hormones we are interested in. The biochemistry analysis is going very well though, and we’re all looking forward to having some data to play with in the coming months.
The biochemistry and ELISA work I’m doing is currently on hold however, as I have returned to the University of Liege in Belgium to work with the Centre de Recherche Analytique et Technologique (CART) to detect the amounts of persistent organic pollutants (POPs) in the blubber of our study seals from the Isle of May last year. We will be using Gas Chromatography – Mass Spectrometry (GC-MS) again, which requires a lengthy extraction and clean up process before the blubber tissue can be analysed (see these blogs from last year for more details) so I will be here for a month to work on our samples (and I will update the blog every week while I am visiting CART). It is always interesting, and more than a little sad, to find out how many pollutants all the seals have inside them after we got to know so well during the field season…
The time has come for the PHATS team to pack up and go home as almost all the grey seals have left the Isle of May and returned to sea. We have all got back to mainland safe and sound, and everyone is looking forward to some well earned rest after almost two months of fieldwork. All of our laboratory equipment and samples were packed up and shipped off the island without incident, and everything is now at our labs at Abertay University and the Sea Mammal Research Unit, ready for analysis in the new year.
There were only nine of our study weaners still on the island during our last survey, and the majority of them are on the edges of the colony ready to go to sea. Oscar is still hanging out in his pool off the south end of the island, and Papa and X-ray have both made it to the bottom of the southern cliffs and are playing and dozing with a bunch of other weaners there. Hopefully they will all find their way out to sea and learn to forage and catch fish in the coming months. Even if they do survive their risky first year, it’s sadly unlikely that we’ll see them anytime soon on the island again. Grey seals usually don’t come back to breed for at least five years if they are female and even longer if they are male. If they do return to the colony however, we’ll be able to identify them from the number on their orange flipper tags, and if you see any seals with tags please do let us know so we can work out which of our study animals you saw.
These kind of mark-recapture methods are used in all sorts of studies on many different animal species, which I was reminded of during the last weaner survey before we left. While searching the southern cliffs I came across a shag with a ring on its leg, which marks it as one of the study individuals the Centre for Ecology and Hydrology has captured, ringed and released back into the wild to help collect data on seabird population dynamics and behaviour. If you see a ringed shag (the leg rings can be several different colours, not just yellow with black writing like the one I saw below) please email the sighting information to email@example.com and if you are interested in the project’s work then you can keep track of what is happening through their twitter feed @CEHseabirds. This particular bird was ringed as a chick in 2000 on the Isle of May, which makes her 16 years old and she has raised 26 chicks so far in her life (information courtesy of the Centre for Ecology and Hydrology).
The PHATS team will be back out in the field in January 2017, when we will return to the Isle of May to look for moulting grey seals. The majority of individuals will enter the moult later in the year at around March/April time, but there are always some seals that start early. We will resume blog updates then, so in the meantime we all wish you Merry Christmas, a Happy New Year and hopefully see you in 2017!
Thus far in this blog I’ve mostly focused on talking about the grey seal mothers and pups which live on the breeding colony here on the Isle of May. The PHATS project only involves collecting data from mothers and pups at various ages, hence I’ve somewhat ignored the other occupants of the colony up to now. However, the other individuals on the colony show plenty of interesting behvaiours too, so this particular blog is going to be about the male grey seals that live on the Isle of May at this time of year, waiting to try to compete for opertunities to mate with the females.
Male mating tactics in species of pinnipeds (seals and sea lions) tend to depend on how sexually dimorphic (differences in size or external features like horns between males and females) the species is and the type of habitat they breed in. Some pinniped species, such as elephant seals, have males that are much larger than the females of their species. This facilitates establishing a territory on a breeding colony that contains as many females within it as possible, defending it from rival males and keeping lots of females inside. These huge males will fight any other males that intrude in the territory to prevent them from entering and mating with the females within. Other pinniped species that breed on ice in the north and south poles of the world use physical features like breathing holes to define where males establish territories, like Weddell seals in Antarctica. Male Weddell seals are a similar size to their female counterparts and use complex vocal displays underwater to defend their territories around breathing holes rather than physically fighting with other males.
Grey seal males show a variety of mating strategies on and around breeding colonies. Males in this species are not much bigger than the females, so creating and guarding large groups of females to mate with (a harem) is not possible. Some males do establish loosely defined territories across various areas of the breeding colonies, but these do not seem to be anchored to physcial features or resources in the colony. The males that compete to stay within the colony amongst the females are called as tenured males and they typically the largest males on the colony, fasting to hold their position in the colony for as long as they physically can before they must return to sea to feed. However, there are alternative mating strategies that males can use to gain opportunities to access receptive females, including intercepting females that are returning to sea when leaving the breeding colony and mating with females at sea. Some male grey seals do return to sea and engage in shallow and deep diving behaviour during the breeding season, but whether these can be attributed to feeding, displaying to attract mates or aquatic mating with females is not currently know. Therefore there seems to be a variety of mating strategies that individual male grey seals can employ on breeding colonies to gain access to females, and future research will hopefully help us understand which are the most successful and how selection pressures have encouraged the development of the different mating tactics.
The PHATS research project is almost complete as the end of the field season is quickly approaching. We only have two samples left to collect, then we will pack up and head off the island just in time for Christmas! Over half our study weaners have now gone to sea, there are only 13 left on the island. The oldest remaining seal is India at 49 days old, but we still have some fairly young weaners like Eel (not in the phonetic alphabet I know but we always run out of alphabet and have to start giving study weaners name codes like AA, BB, CC… and Eel is EE!) who is only 26 days old and still over 50kg. She could hang around the island for quite a long time with all that blubber mass, we have known weaners to remain on the colony for over a month after weaning.
Sadly, while doing the daily colony survey to find our study weaners I also found a weaner that had plastic wrapped around his neck. I managed to deprive him of his ‘necklace’ and he swam off into a pool without serious harm, but it’s a sad reminder of how abundant marine litter is, and how it can cause deadly problems for marine life around our shores. Please be aware of your litter, whether you are on the coast or anywhere outdoors as many speices of creatures can end up trapped or eating the things we throw away, causing severe health problems that they frequently cannot alleviate by themselves.
MEANWHILE Away from the colony,we had some visitors for the day this week as some people from Scottish Natural Heritage came out to the island to prepare for the field station closing down for the winter. There are people living on the island almost every month of the year as bird researchers come out in the spring and stay studying the birds until early october, then the seal researchers move in until mid December. However, between December and spring there are a few weeks when no one is living and working at the field station so everything had to be cleaned, packed away and locked up against the winter storms. It was nice to see some new faces after 2 months of seclusion and everyone had a great day despite the choppy sea conditions getting to and from the island!
The island has also become noticeably more noisy in the last week as the cliffs have become covered in sea birds returning from offshore early to roost. We currently have lots of guillemots
and fulmars on the cliffs and it is lovely to see some more life on the island, especially now there are so few seals around. With the seals departing, and our project coming to an end this year, we will likely be leaving the island in the next week to head home. Going back to mainland after a few months away from society is always a little strange, but everyone is looking forward to seeing their loved ones (and getting regular showers again!).
Even though it’s december and the vast majority of the seals on the Isle of May breeding colony have already raised their pups and returned to the sea, we are still seeing a few newborn pups from mothers that are late season breeders. Most of the colony is quiet now as the majority of adult females have gone, leaving their weaned pups (weaners) in their 2-3 week post-weaning fast (see this blog for more details about the post-weaning fast in seal pups).
Back at the PHATS lab, things are starting to wind down. We had to ship all the samples we had generated so far from the cell culture experiments off the island this week as we had filled the minus 80 freezer on the island! The tissue, media and blood samples we’ve collected over the last 6 weeks will give us plenty to study back on the mainland in the new year. Our daily surveys of the study weaners have shown that two of our weaners, Charlie and Alpha, have left the island and gone to sea! Charlie was 35 days old when she left the colony, and Alpha was 43 days old. Some of our study weaners don’t seem very keen to go, both Bravo and Delta are 43 days old and still happily playing around on the island! Some of our seals are making their way through the colony and the rocky tidal region of the shore towards sea, like Foxtrot who is 40 days old and is on the southern edge of the island.
MEANWHILE the research team on the island has dropped to just 4 people as half the team left the island this week to return home, the remaining two researchers from the Durham University seal behaviour team and two research assistants from the Sea Mammal Research Unit of St Andrews. We also were lucky enought to be visited by one of the bird researchers from the Center for Ecology and Hydrology again, as they keep track of the ringed sea birds (shags) on the island during the winter. During this visit they caught and ringed a wild short-eared owl and were kind enought to show us before they released her, beautiful!
It’s currently my favourite time of year on grey seal breeding colonies, when the weaned pups (weaners) start to out number the adults on the island. I do enjoy watching the huge variety of behaviour the adults display, from the caring maternal behaviour mothers exhibit to the impressive battles males fight for access to females, but the weaners are without a doubt my favourite. This is because they typically spend several weeks on the island after weaning in a post-weaning fast, where they stay on the breeding colony despite there being no food for them, and they usually spend this time playing and exploring their surroundings. They can be very curious, and some will even come right up to you when you’re hiding in the colony to see what you are, play with youre belongings or even fall asleep on you!
Post weaning fasts are common in Phocid (true seal) seal species around the world, from the huge elephant seals to the two species we get in the UK, grey and harbour seals. No one really knows conclusively why weaners stay on the breeding colony for several weeks after their mothers wean them, although there are lots of theories. Grey seal pups can lose half a kilogram of mass every day they remain on the colony after weaning, and as having large amounts of blubber increases the chances that the pup will survive it’s first year of life, it seems very strange that pups stay on the island rather than go to sea to learn to forage and catch fish. However, there is evidence that during the post weaning fast, pups undergo physiological changes which prepare them for going to sea for the first time, so they can hold their breath and perform deep dives so they can catch fish successfully. In grey seal pups, the amount of oxygen they can store in their blood increases during the post weaning fast due to changes in the volume of blood they have and its components, with increases in substances such as hemoglobin that bind oxygen. The more oxygen a pup can store in it’s blood before it dives, the longer it can hold it’s breath and forage underwater, and in theory the more successful at catching fish it will be.
There are still many unanswered questions about the post weaning fast phocid seal pups go through and what happens once weaners leave the colony for the first time. To try and answer some of these questions, one of the senior scientists (Dr Sean Twiss of Durham University) here on the Isle of May is currently looking for a PhD student to investigate “Patterns of individual variation in post-weaning behvaiour in wild grey seals“, and the project is being co-supervised by my boss, PHATS team leader Dr Kimberley Bennett of Abertay University! The deadline for applicants is the 20th January 2017, and if you are interested, the details of the project and how to apply are found here. Whoever gets the PhD will get to come out to the Isle of May next year and will meet me and the rest of the PHATS team! Matt Carter of Plymouth University, another PhD student that Dr Bennett co-supervises, is also currently investigating the development of foraging behaviour in pups leaving breeding colonies, so hopefully in the coming years we will gain a much better understanding of the factors driving weaner behaviour before and after they go to sea for the first time.
In the lab here on the island the PHATS project is just over halfway to completion this year. As it gets later in the breeding season we are getting more and more study weaners to keep an eye on, although some of the first weaners that we included in our study are approaching the time when they may go to sea for the first time, at about a month of age. Charlie is now 35 days old and much leaner than when she first weaned from her mother 17 days ago, having lost 9.6kg across those 17 days. This seems like a lot, but considering she put on 22.2kg of blubber in the 18 days she was with her mother, she is still large enough to successfully go to sea. Kilo has now fully moulted and has a very distinct pattern of spots that we can identify him from. We also have a new study weaner (Oscar) that has moulted and turned out to be completely black!
MEANWHILE away from the colony, it briefly got a little bit harder to escape from the seals as a female came right up outside our doorstep with her pup for the first time! She has thankfully moved on a little further from the house so we don’t disturb her, but it was a suprise to open the door one morning and find the pair of them staring at us!
Sadly two members of the research team here have had to leave the island in the last week, Dr Twiss and Dr Bennett both had to return to the mainland to resume their teaching duties at their universities. They will be missed, and it marks the beginning of the end of the field season as the majority of the researchers here will also leave in the coming week. The PHATS team will stick it out until mid December, but it’s always sad to see people go!
Finally if you’d like to see Dr Bennett talking about seals or the PHATS project, she will be giving some public presentations in the coming weeks in Scotland:
6pm, Tuesday the 13th December at the D’Arcy Thompson Zoology museum at Dundee University: Public talk on seal biology
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!