Wednesday, 6 March 2013

Keep alive and carry on

The story of one of the winter research projects carried out on the island. 

Keep alive and carry on: My experience in the Isle of May during grey seal pupping season 2012.
Please, it is strongly recommend that when reading the following listen to:
1.       Seal - Crazy
2.       Pearl Jam – Alive
3.       Kansas – Carry on my wayward son
4.       Simple Minds – Alive and kicking
5.       Bee Gees - Stayin’ alive
My name is Martina and I am here to share my story.
Everything began when I started my PhD at the University of Glasgow in 2011. My project title was ‘The role of the marine mammal carrion in the ecology of the coastal marine system’… “
Marine mammals may have an important influence on ecosystems they are part of, because of their size, mobility and abundance. But, when they die, they have the greatest impact on the recycle of nutrients, as their body becomes a source of food for other animals.
The Isle of May, during winter hosts one of the largest grey seal colonies of UK. Between October and December seals come to the island for pupping and breeding and during this period the species experiences its highest mortality, which can reach up to 30%. Between birth and weaning, pups can die for a whole range of different reasons. For instance trampling and wounds due to interactions between adults and pups may lead to severe injuries or infections and finally to death. The incidence of starvation in pups is very common as well, and it is almost certainly due to the failure of formation, or the breakdown, of the bond between mother and offspring. The latter can happen on crowded breeding sites due to disturbance which can be caused by adjacent adults, storms, high tides or humans, and also due to pups wandering away from their mothers and becoming lost. 

Such carcasses of neonate seals may attract opportunistic birds or mammals that would transfer marine-derived energy inland, like seagulls, crows or mice. Moreover, when carrion is washed off because of high tide or storms, marine organisms can consume it.

Therefore, the Isle of May was for sure the best place where to carry out my fieldwork. I spent six weeks there with a few other researchers, with whom I shared one of the best experiences of my life. 

 I had never been in such close contact with wildlife before going to the Isle of May. Grey seals are such big animals, and, honestly, at the beginning I was very scared of them (the live ones). When mothers protect their pups, they can be very aggressive and I was not used to their usual reaction. To increase my confidence with seals, I had to face daily a pup, which decided to share the hide with me, but not very happy of my presence, it was crying all of the time. Despite my imploring, it never gave up in calling its mum. Results: for the first days, I was constrained to work outside her hide, hidden by the lovely seal family. 

Part of my typical day in the Isle of May was making observations of gulls scavenging on dead pups occurring in the Loan and East Tarbet. Gulls visiting the two areas were mostly Great Black Backed Gulls and juveniles, which behaved opportunistically feeding not just on carcasses, but on vomit and placentas as well! A new born was, in fact, always celebrated by very noisy gulls that cry and fight to have a piece of fresh placenta. However, they were behaving differently with dead pups as they could spend from few minutes to hours on the same carcass, partially avoiding competition among individuals. Generally, the first bird to exploit carrion is that one who can open it. Unfortunately I did not spot any Golden eagles in the Isle of May, although it would have been such great fun. Here, the Great black backed gull is the largest bird with the best capability in using its beak to penetrate the body. So, generally it opens first the carcass. Instead, juvenile individuals, because of their inexperience in catching food, opportunistically feed on the corpse once opened by adults. In the Isle of May there were just few carrion crows and I did not detect them on carcasses, but it is known that usually they arrive at the latest stages of the carcass consumption to not compete with gulls.
Gulls never forget to wash their mouth after eating: once they finished they were immediately washing their beak into the sea!

As seals and gulls share the same areas, interactions among them are inevitable. When a gull pecked a pup to understand if it was alive, it was at high risk of bite from the seal mother. Lots of inexperienced young gulls showed, in fact, injuries on their wings or legs. Broken Wing was one of them. I regard him very highly, because, even if disabled, it was putting all its efforts to survive through the winter. 

Depending on the location where a pup dies, it becomes source of food available to different scavengers. According to the topography and weather conditions, pupping areas could be affected by tide or storms which can increase mortality, but also move carcasses into the water. When a carcass is underwater, scavengers living on the seabed feed on it. Among them, gastropods as nassariids, shore crabs, but also other small crustaceans like amphipods and fish.
For this purpose, I ran an experiment in the sea water pool occurring at Foreigner Point: by using a heavy frame equipped by an underwater camera, I recorded the initial consumption of a small carcass. Despite the high number of marine scavengers, the underwater process of consumption is very long, not just because of their size, but also because their less effective capability in breaking the body.  

Evaluating the carrion inputs available to the marine system results very difficult, but outside of the water this can be achieved more easily. At the end of the season I and my islander mates surveyed all island to estimate the total biomass available to scavengers deriving from pup mortality. The number of carcasses found was 233, whose total weightwas estimated more than 5 thousands kilograms, which are potentially available to the wintering gulls of the island.
One of the original etymologies of the name “Isle of May” is the island of gulls.
My story is not a sad story, but it’s the celebration of life after death.
And now listen to Bee Gees again!

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