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Duncan Murrell - A Whale of a Time

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Duncan Murrell - A Whale of a Time

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17 images Created 15 Nov 2014

Seals and Sea Lions

When I was out on the sea I often encountered harbour seals or Steller sea lions. They are markedly different in their characteristics; harbour seals are very shy and would usually pop their heads up furtively behind my kayak, but Steller sea lions were always inquisitive, if not a little wary, and would always investigate me as close as they would dare, and often race alongside me. The sea lions never failed to entertain with their loud, boisterous and sometimes playful behaviour. Seal haul outs are usually comatose places compared with the lively circuses that are sea lion haul outs. Getting close to the sea lions was always much easier than the seals because of all the commotion and pandemonium, especially when the big bulls were sparring. The average adult male Steller sea lion is about 1,250 lb (560kg), but can double that weight and reach a length of 10 ft. The females are from 7.5 ft – 9.5 ft ( 2.30m- 2.90m) in length and can weigh up to 770 lb (350kg). They are opportunistic feeders and eat a wide range of fish, and need to eat about 5-6% of their body weight a day. When the males are defending their territories they may go without eating for over a month. They are divided into a Western and Eastern population in Alaska. There have been drastic declines in numbers, especially in the west, but it now appears that their numbers have stabilised, and showing small increases.
The average weight for harbour seals in Alaska is about 180 lbs (82kg), with males weighing up to 285 lbs(129kg). They can reach 5-6 ft (1.7-1.9m) in length. Like the sea lions they are opportunistic feeders and take advantage of seasonally available prey. They are able to dive up to depths of 1640 ft (500m) and can remain submerged for over 20 mins. Like the sea lions they are as graceful in the water as they are ungainly on land. Their numbers have also fluctuated in different parts of Alaska. As with the sea lions the reasons are unknown but multiple factors are likely involved.
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  • Reproductively mature male sea lions aggregate on traditional rookeries in May, usually on beaches on isolated islands. A week or so later, adult females arrive, accompanied occasionally by sexually immature offspring, and form fluid aggregations throughout the rookery. Steller sea lions are polygamous but they do not coerce individual females into harems but control spatial territories among which females freely move about. Pregnant females give birth soon after arriving on a rookery, and copulation generally occurs one to two weeks after giving birth, but the fertilized egg does not become implanted in the uterus until the autumn. After about a week of nursing, females start taking increasingly longer foraging trips, leaving the pups behind until in late summer when they both leave the rookery. Males fast until August, often without returning to the water, after which time the rookeries break up and most animals leave for the open seas and disperse throughout their range.<br />
Steller sea lions are predated upon by orcas and I actually witnessed the death of one bull that had become quite attached to me. It had been showing so much interest in me and it even raised its head out of the water right in front of me to have a good look with its bulging eyes. A short while later I heard a commotion in the distance and saw that a pod of transient orcas had arrived on the scene and were systematically charging the sea lion and thrashing it with their flukes. It was a difficult event to witness, especially whenever the big bull re-appeared on the surface gasping for breath. It took the orcas about 15 minutes to finally kill it and not long after that they were attacking some humpback whales that had strayed onto the scene. It was an exhilarating experience to be paddling my kayak so close to a pod of orcas engaged in a hunt, but they showed no interest in me. It was one of those occasions when I wished that I’d had someone else with me to witness such an amazing spectacle.
    Alaska-Steller-sealion1.jpg
  • Reproductively mature male sea lions aggregate on traditional rookeries in May, usually on beaches on isolated islands. A week or so later, adult females arrive, accompanied occasionally by sexually immature offspring, and form fluid aggregations throughout the rookery. Steller sea lions are polygamous but they do not coerce individual females into harems but control spatial territories among which females freely move about. Pregnant females give birth soon after arriving on a rookery, and copulation generally occurs one to two weeks after giving birth, but the fertilized egg does not become implanted in the uterus until the autumn. After about a week of nursing, females start taking increasingly longer foraging trips, leaving the pups behind until in late summer when they both leave the rookery. Males fast until August, often without returning to the water, after which time the rookeries break up and most animals leave for the open seas and disperse throughout their range.<br />
Steller sea lions are predated upon by orcas and I actually witnessed the death of one bull that had become quite attached to me. It had been showing so much interest in me and it even raised its head out of the water right in front of me to have a good look with its bulging eyes. A short while later I heard a commotion in the distance and saw that a pod of transient orcas had arrived on the scene and were systematically charging the sea lion and thrashing it with their flukes. It was a difficult event to witness, especially whenever the big bull re-appeared on the surface gasping for breath. It took the orcas about 15 minutes to finally kill it and not long after that they were attacking some humpback whales that had strayed onto the scene. It was an exhilarating experience to be paddling my kayak so close to a pod of orcas engaged in a hunt, but they showed no interest in me. It was one of those occasions when I wished that I’d had someone else with me to witness such an amazing spectacle.
    Alaska-Steller-sealion2.jpg
  • Observing sea lions at close quarters at their haul-outs was like going to a circus, because there always so much going on to entertain and amuse. They are such noisy and smelly places, and sometimes I had to crawl through the foul, stagnant rockpools to get amongst them, but it was always worth it. There was often sparring going on between the big bulls, which involved a lot of heaving and wheezing, and roaring. If they weren't sparring then they would be posturing in  a high and mighty fashion with their heads thrown back and their chests puffed out. Younger bulls appeared to congregate in gangs like delinquents hell-bent on mischief, usually directed at the less mobile larger bulls. One of the funniest incidents I have ever seen in the animal kingdom was when there was a big bull teetering on a narrow ledge on a rock-face about 2 metres above the sea. Beneath him there were some mischievous juveniles that were leaping up at him out of the water to nip him on his exposed posterior that he was unable to protect because of his precarious situation. He was getting understandably very irritated, and eventually fell off the narrow ledge into the sea making a big splash: it was hilarious! I also enjoyed watching the juveniles playing in the tidal surges that swept them back and forth along channels between the rocks. Sometimes when I was paddling in big swells with waves crashing onto the rocks I marvelled at how the sea lions revelled in the opportunity to play close to the rocks in sea conditions that were threatening to me.
    Alaska-Steller-sealion3.jpg
  • Steller sea lions forage near shore and pelagic waters.They are also capable of traveling long distances in a season and can dive to approximately 1300 feet (400 m) in depth. They use land habitat as haul-out sites for periods of rest, molting, and as rookeries for mating and pupping during the breeding season. At sea, they are seen alone or in small groups, but may gather in large "rafts" at the surface near rookeries and haul outs. They are capable of powerful vocalizations that are accompanied by a vertical head bobbing motion by males.<br />
Steller sea lions are opportunistic predators, foraging and feeding primarily at night on a wide variety of fishes (e.g., capelin, cod, herring, mackerel, pollock, rockfish, salmon, sand lance, etc.), bivalves, cephalopods (e.g., squid and octopus) and gastropods. Their diet may vary seasonally depending on the abundance and distribution of prey. They may disperse and range far distances to find prey, but are not known to migrate.<br />
Steller sea lions are colonial breeders. Adult males, also known as bulls, establish and defend territories on rookeries to mate with females. Bulls become sexually mature between 3 and 8 years of age, but typically are not large enough to hold territory successfully until 9 or 10 years old. Mature males may go without eating for 1-2 months while they are aggressively defending their territory. Males may live up to 20 years and females to 30 years. Females start breeding at 3-7 years and spend the next two decades either pregnant or lactating. Females are bred in June, but the fertilized egg does not implant until October. Single pups are born the following June, with birthdates at southern rookeries earlier than births at northern rookeries. Twins are rare. Pups suckle from 1 to 3 years, with most apparently weaning after their first winter.
    Alaska-Steller-sealion4.jpg
  • Yasha Island was my regular place for observing, photographing and simply being entertained by sea lions. I had to land my kayak on the opposite side of the islet, creep stealthily through the rocks and trees, and then low down on my belly to get right in amongst them. There is usually so much noise and commotion at a haul-out that it's surprisingly easy to get in amongst them. Their vision is evidently quite poor out of water, so as long as I moved very slowly and didn't stand up and become boldly silhouetted, I could "bluff" my way into their close company. Sometimes one of them would stare at me inquisitively but as long as I kept completely motionless, it then continued participating in the general pandemonium that frequently pervades the haul-outs. But sometimes a degree of calm is restored as this photo illustrates, but it takes just one incident to flair up, perhaps when one of them is rudely awakened by the clumsiness of another one trying to get past it, and then the pandemonium sweeps across the haul-out like a wild fire with their extended heads swaying in the air belching out disgruntled roars and groans.
    Alaska-Steller-sealion5.jpg
  • The sea lions have such a thick coating of blubber to cushion their bodies that they can sleep just about anywhere and look very comfortable. It is a different matter when they are trying to haul their bulky bodies around with only their flippers to assist them. It involves a lot of huffing and puffing, heaving and swaying with much grunting and steam belching from their open mouths. They look like big sacks of blubber and bones being dragged across the rocks: in stark contrast to their fluid graceful motion underwater like huge flying fish.
    Alaska-Steller-sealion6.jpg
  • The Steller sea lions of Alaska have entertained me many times and provided company during bad weather when there were no other animals around. They were always inquisitive, if not a bit wary of me, and would often swim beneath my kayak and look up at me with their big bulging eyes. Sometimes they would even engage me in a race to show off their speed on the surface where they can leap like dolphins.<br />
Among pinnipeds, it is only inferior in size to the walrus and elephant seals. The males are bigger than the females and grow to a length of about 2.82-3.25 metres long, with an average of 3m. The males have much wider chests, necks and general body structure and weigh 450-1.120 kg with an average of 544 kg. Males are further distinguished from females by broader, higher foreheads, flatter snouts, and darker, slightly tuftier hair around their large necks, giving them a maned appearance. Indeed, their Latin name translates roughly as “maned one with the broad forehead”.<br />
The range of the Steller sea lion extends from the Kuril Islands and the Sea of Okhotsk in Russia to the Gulf of Alaska in the north, and south to Ano Nuevo Island off central California. The global Steller sea lion population has traditionally been divided into an eastern and western stock roughly through the Gulf of Alaska. They have attracted considerable attention in recent decades due to significant, unexplained declines in their numbers over a large portion of their range in Alaska. While the population of the eastern and Asian stocks appear stable, the population of the western stock, particularly along the Aleutian Islands, was estimated to have fallen by 70-80% since the 1970s. One suspected cause of their precipitous decline is overfishing of Alaska Pollock, herring and other fish stocks in the Gulf of Alaska. In 1997 the western stock was listed as threatened but in 2013 they were removed from the U.S Endangered Species List after a major population recovery.
    Alaska-Steller-sealion7.jpg
  • If I paddled past a sea lion haul-out I always attracted a tightly-packed group of noisy sea lions like a magnet: they would extend their heads as high as they could to get a better look at me. They always stayed bunched together rather like a shoal of fish that employs the "one in the middle" defensive group strategy that relies on strength of numbers to increase an individuals chance of survival. They were very vociferous but always kept a safe distance, unless they dived underwater to get a closer look at me: I could see them circling beneath me and looking up at me with their big bulging eyes.
    Alaska-Steller-sealion8.jpg
  • They are opportunistic feeders and eat a wide range of fish including herring, Pollock, salmon, cod and rockfish as well as squid and shrimp. I have even observed them catching seagulls on the surface.
    Alaska-Steller-sealion9.jpg
  • I often used to creep up close to the sea lions hauled out on Yasha Island, just off Point Gardiner at the southern end of Admiralty Island. I could see this young sea lion laying down on its belly, and that it had something around its neck, but nothing could have prepared me for the gut-wrenching sight when it reared up and I could see the full extent of the damage and suffering that this poor creature must have endured. The net had become deeply embedded in its throat as it had continued to grow after first getting entangled with it when it was probably playing with it. One strand of the net passed through its mouth like a horse's bit, and had pulled its mouth back into a horrific frozen grimace. I felt so sickened by the daily torture that this poor animal must have been subjected to, but it also seemed like it had somehow adapted to it demonstrating the incredible resilience of wild animals. Apart from its horrific embedded necklace it looked just as well fed and healthy as the other sea lions. I felt compelled to try to capture it without really knowing how I could hang onto the sea lion to remove the net, but I wasn't able to get close enough without disturbing all of the sea lions. When I returned to Petersburg I reported it to the Dept of Fish and Game, and was glad to hear that they were going there to do a survey, but unfortunately I later heard that they were unable to find the poor animal. I don't know how much longer that it would have been able to survive like this if it was still growing.<br />
This kind of entanglement in fishing nets is a major problem for all marine life, but it must be particularly so for sea lions because they are so inquisitive and playful. A few years later I was working on a whale research boat in Sri Lanka, and we came across two turtles entangled in a big clump of fishing net, but fortunately we were able to free them.
    Alaska-Steller-sealion10.jpg
  • The harbor seal (Phoca vitulina), a widespread species in both the north Atlantic and Pacific oceans, is found in Alaska along the coast extending from Dixon Entrance north to Kuskokwim Bay and west throughout the Aleutian Islands. Harbor seals, and other phocid (true) seals, also are called “hair” seals, which helps distinguish true seals from fur seals. Harbor seals haul out of the water periodically to rest, give birth, and nurse their pups. In winter seals spend up to 80% of their time in the water. In spring and summer they spend more time hauled out during pupping and moult season. Reefs, sand and gravel beaches, sand and mud bars, and glacial, pan ice, and sea ice are commonly used for haul-out sites. The moulting lines on these seals are clearly visible.
    Alaska-harbour-seal1.jpg
  • Harbor seals show variable movement patterns depending on their sex and age class, with some exhibiting considerable localized travel but noseasonalpatterns,whileothersshowmoreextendedmovements,particularlyduringthewinter. Seasonaluseofglacialfjords,wheremanyfemalesaggregateto give birth on icebergs in the summer, is common. Satellite tagging studies have shown that pups may range up to 232 miles (374 km) from their birth site, although most movements are less than 62 miles (100km) away. Juvenile seals can make more extensive movements of up to 186-310 miles (300-500 km) away from their tagging location; however, most remain within 100km. Adult seals typically make shorter movements and on average are within 37 miles (60km) of their tagging site. More recent tagging of seals that occupy glacial fiords has revealed movements of seals from one glacial fiord to another as well as one extensive movement of a juvenile female seal from Glacier Bay in southeastern Alaska to Prince William Sound, an estimated straight-line distance of ~ 520 miles (830 km). As more seals are being satellite-tagged, much more information is becoming available about winter and summer movements.
    Alaska-harbour-seal2.jpg
  • In Alaska, single pups are born between May and mid-July. Young pups are able to swim almost immediately after birth. They normally remain with their mothers about one month, after which they are weaned and separate from their mother. At that time over half their body weight may consist of fat, providing them a head start on self-sufficiency.While harbor seals will often voluntarily swim close to humans on beaches or in small boats, seals resting on land or ice are wary of people and will rush into the water if approached too closely. If disturbed too often, seals have been known to abandon favorite haul-out sites or their pups. I was able to approach this sleeping seal pup close enough to touch it. They are usually much more alert than sea lions because there is less distracting noise and commotion. I have always been extremely careful not to disturb any of the animals that I have stalked.
    Alaska-harbour-seal3.jpg
  • The most common predator of harbor seals is the killer whale. Other predators include sharks, sea lions, and land predators such as wolves, bears and coyotes. Since implementation of the Marine Mammal Protection Act in 1972, hunting has been restricted to Alaska Natives. Harbor seals play a crucial role in the culture and diet of Alaska Natives; the annual subsistence harvest of harbor seals in Alaska is about1,800 to 2,900 animals, with fewer seals harvested in recent years. The harbor seal's ability to damage or remove salmon from gillnets has caused conflicts between seals and commercial fishers in Alaska. This behavior creates economic losses for fishers and often fosters an antagonistic attitude toward seals. The Copper River Delta, the mouths of the Stikine and Taku rivers, and portions of Bristol Bay are areas with notable harbor seal-fishery conflicts. Sometimes seals are caught and killed or injured in fishing gear, primarily in gillnets and occasionally in crab pots.
    Alaska-harbour-seal4.jpg
  • Dramatic declines in harbor seal numbers have been documented in Alaska, including a decline from approximately 11,000 seals to 1,000 seals during 1976-1988 on Tugidak Island near Kodiak – a site previously considered to host one of the largest concentrations of harbor seals in the world. That decline resulted in the listing of Alaskan harbor seals as a species of special concern by the Marine Mammal Commission. A 63% decline in harbor seal numbers also occurred in Prince William Sound during 1984-1997. Although seal numbers in the Kodiak area have been steadily increasing since the early 1990s and seal numbers in PWS began to stabilize and show signs of increase in 2002, both populations remain severely depressed compared to pre-decline population levels. Similarly, a greater than 65% decline in seal numbers has been documented in Glacier Bay since the early 1990s. Seals in Glacier Bay continue to decline at a precipitous rate despite conservation measures in place to control vessel traffic, commercial fishing, and subsistence harvest. The declines and lack of substantial recovery of some harbor seal populations in Alaska contrasts sharply with other parts of the world, where the species has proven to be resilient and capable of fairly rapid recovery from perturbations. There is no evidence that movements of seals between areas can explain these declines; the cause is unknown, but multiple factors are likely involved. Harbor seals appear to have responded severely to changes in carrying capacity and therefore may be particularly sensitive indicators of future change, such as ocean warming.
    Alaska-harbour-seal5.jpg
  • The total Alaska harbor seal population is estimated at approximately 141,000 in non-glacial sites and approximately 15,000 in glacial fjords. Harbor seals are difficult to census because they can only be accurately counted when they are hauled out. They haul out at different times of the day at thousands of locations in Alaska; both at terrestrial sites and on glacial ice calved from tidewater glaciers. During any survey, some seals are in the water and not available to be counted while others are hauled out, but the proportion of the total population hauled out at any given time is unknown and must be estimated. One way to arrive at this estimate is to radio tag seals in the area, prior to conducting a survey. When the survey is conducted, the proportion of radio-tagged seals that are not hauled out provides a correction factor to estimate the total seal population (e.g., if 3 of 10 tagged seals were not hauled out, an additional 30% would be added to the count of seals hauled out to estimate the total population).
    Alaska-harbour-seal6.jpg
  • Harbor seals (Phoca vitulina), are “true seals” of the Phocidae family, also sometimes called “common” or “hair” seals. They are covered with short, stiff, bristle-like hair. Coloration varies, but two basic patterns occur: light gray sides and belly with dark blotches or spots, or a dark background with light rings. They can be distinguished from other pinnipeds, such as fur seals and sea lions, by the absence of external ear flaps; only a small hole (the external pinnae, or opening to the ear canal) is visible on either side of their head. When on land, harbor seals move awkwardly by undulating in a caterpillar-like motion because their pelvic bones are fused, preventing them from moving their hind flippers under their pelvis to walk. In the water they are graceful and efficient swimmers, using their fore flippers as rudders and their hind flippers for propulsion by clasping both hind flippers together, splaying webbed toes and moving the large hind flippers side to side.<br />
Harbor seals weigh about 24 pounds (11 kg) at birth and gain weight rapidly during a month-long suckling period; perhaps doubling their weight. They can reach five to six feet (1.5-1.8 meters) in length. Average weight for adults is about 180 pounds (82 kg); males are somewhat larger than females and can weigh up to 285 pounds (129 kg).
    Alaska-harbour-seal7.jpg