Monthly Archives: July 2017

Weaned pups and grown-up fights

Once again we are approaching the end of our photo-ID effort at the study sites. Following last year’s pattern, the mood at the haulout sites in Orkney has considerably changed over the last couple of weeks. Most of the pups have been weaned which means the females are free to go foraging before they start moulting.

Pup suckling at one of the haulout sites in Orkney

Pup making the most of the fat-rich milk before weaning time arrives

The haulout sites are now filled with the newly weaned pups, some of which are not quite over the fact that the good days of suckling the fat-rich milk are over. If the opportunity shows, they will try to get some extra feeds from the few females that are still suckling their pups. Despite their best efforts, they tend to get discouraged fairly quickly either by the females or by the pups holding the right to suckle. In the video below you can see a female coming to shore followed by three pups, two of which are just wanting that extra feed. However, they quickly realize that’s not going to happen and go back into the water.

On some occasions females seem to tolerate the presence of a second pup and might allow it to rest near by,  but again, that doesn’t last long if the pup attempts to get too close. That’s exactly what seems to occur in the next video, also captured in Orkney. This female came onshore with two pups and started suckling one (assumed to be hers) while tolerating the presence of a second one of similar size. However she quickly snapped that pup to presumably stop it from approaching any further.

To better understand whether this phenomenon is down to just a few pups or is more widespread, we do try to get pictures of the pups as well as the adults. Because pups are born with their adult coat, they already have a characteristic and unique pelage pattern. By identifying pups we can attempt to estimate how long are pups seen in association with their mothers, how long does the lactation period last and whether pups will suckle from different females.

Female Or098 with her pup on 14th July 2017. This wee guy has a wishbone mark on his left cheek!

Or098’s pup on its own on 16h July 2017. The same wishbone mark can be seen in the pelage pattern on his left cheek.

As pupping season comes to an end, preparations for mating and moult season are well underway. Some of the bigger males have been seen more regularly at the haulout sites in Orkney and have offered all kinds of displays. These go from simple grunting exchanges with other males in the distance, to fast swimming along the haulout sites, throwing seaweed around, as well as proper physical fights. In the next video we captured two harbour seal males fighting; the younger one (smaller) had been warming up by doing the seaweed throwing as well as grunting, and got even crossed with an unfortunate pup that was at the wrong place at the wrong time. Luckily it was all just a big scare and the pup managed to haulout and recover from the unwanted fight. However, the young male kept on challenging a much bigger male, until they started to fight. After a resting period, they both took it back into the water, where full body flips and jumps were seen from the distance. After that, they both rested on land, like nothing had happened.

While the adult males are busy maintaining territories and fighting with other males, some of the younger seals are well into their annual moult, while other adults are just starting it off. The first seals to moult are those with the oldest coat, which will be the pups born last year, as well as the very young seals that also moulted early last year. The old hair is brown and in patches, but the new coat showing underneath displays gorgeous and distinctive black and white patterns. The moult period is an itchy one, and seals can be seen scratching themselves as the old coat gets slowly replaced by the new one. Is in this time of the year when seals spend a higher proportion of time hauled out onshore rather than in the water. The moult is an expensive period in terms of energy, as warm blood is circulated very close to the skin to help the new hair grow quickly. To avoid losing energy by getting cold in the water, seals spent much more time onshore.

Adult harbour seal starting to show signs of the annual moult

Moulting male harbour seal; all the old brown hair will fall and be replaced by the new coat

This young female is already showing her new coat around the head and shoulders

 

Haulout-site neighbors

For the last three weeks I have been a very busy bee in Orkney, hence the delay on updating the blog! The pupping season is advancing with giant steps, pups are getting bigger every day, some others have already been weaned and adults are showing the first signs of the annual moult!

The weather has mostly been on our side with overcast and slightly breezy days, which make photo-ID a much easier job. However, we’ve had our share of sunny and calm days, which make photo-ID a tricky business as the seals look all hazy through the lens and the pelage patterns are really difficult to identify. And there is always the risk of unwanted midges company! Very wet and windy days also pose a challenge as it’s hard to keep the equipment dry and safe.

Sunny and calm day in Orkney = photoID with 10,000 midges.

A couple of weeks ago I spotted a grey and a harbour seal having a nice rest on a hot and sunny day, both with a telemetry tag on. The grey seal was tagged as part of a separate SMRU project, which is collecting data for the Met Office. Grey seals are often seen sharing the same haulout sites as harbour seals, although haulout sites of only grey or harbour seals are also the norm. In Orkney, all the of the monitored haulout sites where we collect photoID data are mainly harbour seal haulouts, but grey seals are also found in smaller numbers. In Loch Dunvegan (Isle of Skye), where Andy collects photoID data, it’s very rare to have grey seals sharing the same skerries, but sometimes there is the odd grey seal that shows up.

 

Grey and harbour seal tag buddies on a hazy day

Grey seal with a telemetry tag on one of the monitored haulout sites in Orkney

Grey and harbour seals have different haulout behaviours. While grey seals seem to be ok hauling out very close to each other, harbour seals prefer to keep a larger personal space around them. If another harbour seal or a grey seal comes too close, they start grunting and moving one of their foreflippers to keep the approaching seal away. Harbour seals will rather get back into the water and find a quieter space than staying too close to a curious grey seal!

Harbour seal looking rather unhappy with an approaching grey seal…

Two grey seals having a snooze at a haulout site in Orkney with harbour seal neighbours

In general grey seals will haulout and rest, but in some occasions some other action can be seen. Sometimes younger grey seals will curiously approach harbour seal pups, or simply stir the tranquility of the haulout by walking through the grey seal haulout, starting a sequence of loud and characteristic grey seal hauling. Last month, as I was taking pictures in Widewall Bay, in South Ronaldsay, I filmed a couple of grey seals playing-fighting at one of the haulouts. In my limited experience with grey seal behavior it looked like a male grey seal playing with a female and making a rather poor attempt at mating.

Despite our main interest being harbour seals, one cannot miss the other wildlife sharing the haulout sites, starting with the many species of birds that can be regularly seen. Black-backed gulls and great skuas patrol the haulout sites in search of a free meal. At the start of the pupping season large groups of greylag geese can be seen at or flying past the haulout sites, generally in a rather noisy way! Oyster catchers and curlews add to the sound track, very often giving away my hiding spot to the seals. At one of the study sites, which sits below a cliff, the seals are accompanied by the constant chatter from fulmars nesting nearby. Redshanks and ringed plovers can be seen on the sandy and pebble shores close to the water, and herring gulls can be often seen walking around the seaweed covered rocks by the water. It turns out they like to eat sea stars!

Ringed plover at one of the haulout sites

Herring gull eating on a sea star

As the summer advances, larger groups of arctic terns are making an appearance at two the the monitored haulout sites, the larger being in Widewall Bay. A couple of weeks ago there was such a large group of them that they frequently photo-bombed my photo-ID effort. I don’t think the seals were very happy with such noisy neighbours!

Arctic terns photo-bombing my attempts to photoID a harbour seal mum pup pair in Widewall Bay

But it’s not all birds among the neighbours… there are also some more infrequent visitors. Last week we had a surprise visit from an otter! She was seen swimming past the haulout site and ended up coming up on shore to undergo a good clean up. She then had a quick rest before going back to the water. I was lucky enough to be close by without being spotted and the digiscope system we use to get photoID data did the rest… check the picture and video below.

Otter spotted near one of the haulout sites in Burray

And finally, another marine mammal that can make an appearance is the killer whale. Killer whales are natural predators to seals, and are regularly seen around Shetland, Orkney and the north coast during this time of the year. I have personally never seen them nearby the haulout sites we monitor, but have seen them in other areas around mainland. Public sightings report them frequently in the Pentland Firth between Orkney and mainland, but also in the waters around Birsay. While going for a walk along Rerwick Head, at the north side of mainland, we were lucky enough to bump into a group of 5 killer whales that were swimming very close by the shore. After the initial excitement we managed to capture them passing by, see the video below. The group seemed to be composed by 1 male and 4 females or juveniles, the male having the very tall and straight dorsal fin. I seemed to recognize one of the females as Mousa, a female killer whale that is regularly seen in Shetland and Orkney waters. This female is also included in the catalogue of killer whales from Iceland (with ID number IS086). Like Mousa, some other individuals repeatedly move between Iceland and Scotland. These whales appear to feed on the Icelandic summer-spawning herring stock in the winter, and then move outside the summer distribution range of this herring stock (check more details on this published paper on the matter). More information on the Icelandic orcas can be found in their website and in their Facebook page

 

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