Half way

The end of June marked the half way point on our photo-identification effort during this year’s pupping season. At least at the monitored haulout sites in Orkney, all females seem to have given birth, as I cannot observe obviously pregnant females anymore. For what Craig tells me, he is still observing a few pregnant females in Kintyre ready to give birth. After all, he was the last one to observe the first pup this year. As for Isle of Skye, Andy has been going our regularly with the boatmen from Dunvegan Castle when the weather has permitted, and has had really good days counting around 130 seals hauled out and 34 pups seen! At the haulout sites in Orkney, numbers are much lower, with around 40 adult seals and 20 pups seen on average at the main pupping site.

Several mum-pup pairs in Orkney, well camouflaged!

With all the new pups around, the haulout sites are busy places. Pups seems to have their own agenda, going into the water quite often and consequently dragging mum behind. When not suckling or sleeping they are curious individuals and will explore their surroundings and neighbors. Other pups seem to be ok with other little ones approaching, unless they are getting too close to their food provider. Some adults tolerate pups that just get close to have a nice spot to rest, but will get rather annoyed with with pups that approach too close, especially if they are after suckling from females other then their mothers. Yesterday I came across a mum pup pair that hauled out right next to another two pups on their own. One of them came closer to inspect, until he got too close and got a grunt from the female (see photograph below).

Lonely pup (back) staring at another pup suckling

Pup climbing over his mum soon after hauling out

After suckling, some pups go straight onto having a nice nap, while others like to move and play around for a bit, like this one:

At this time in the pupping season, it is normal to observe pups on their own. Female harbour seals will go on short foraging trips during this time, and come back shortly after to suckle their pup. While this is normal for seals, it makes photo-ID life a little bit more complicated as it becomes a bit more difficult to link pups and adult females. Patience is definitely a key element. Sometimes pups left on their own will fall asleep totally unaware of what the tide is doing. When they fall asleep while the tide goes down they then wake up rather far away from the water, as it happened to this pup:

Lonely pup waking up rather far away from the water’s edge!

On a couple of occasions I have witnessed female harbour seals accompanied by two different pups. While twin births are rather rare in seals, fostering is a more frequent event. Sometimes inexperienced mums which might have had their first pup will get confused at a second pup approaching and will allow it to suckle. If a pup gets abandoned to somehow separated from its mum, it will try to suckle from other females. In both occasions, one of the pups seemed to be of smaller size and weight than the other one, which makes me think it was an abandoned pup not feeding as much as needed. In both cases the female seemed to be snappy at times with the second pup and at the end left into the water with just the bigger pup. Having to suckle a second pup is likely to have a detrimental effect on the survival probability of both pups, as resources have to be split and they might not put enough weight before getting weaned. At the same time, it might also have a negative effect on the female’s fitness condition at the end of the pupping season, potentially having had to use more energy resources than anticipated and potentially compromising her fitness for the next steps in her yearly cycle.

Female harbour seal with two pups. The one on the right was obviously much smaller than the other one. Both pups managed to suckle from this female.

A different female harbour seal with two pups again. After suckling the pup on the left, the female ended up swimming away with the pup on the right, which looked bigger.

Blog entry written by Mònica


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