Sea lions-pride of the southern seas
Like an Amazonian hunter , blowpipe at the ready, the zoologist stalks his quarry. Halfcrouching, his every movement slow, deliberate, noiseless, he lifts the metre-long pipe to his mouth, takes aim, and, with cheeks bulging, delivers a blast of air down the pipe.
P000phhh! A syringe with a fluffy tail bites into golden fur and discharges its contents into the muscular flank of a recumbent female sea lion. The animal, full-grown and weighing 130 kg, scarcely flinches, but she seems to know that something strange is happening. Raising herself up on powerful foreflippers, she sniffs the brown pup at her side as if to reassure it, then begins wandering towards the nearby rata forest with a steady rolling gait.
The syringe dart drops to the ground and is collected. The sea lion walks on into the gnarled “goblin” forest, with the scientist following. His job is only just starting.
Nick Gales is a sea lion specialist based at the Department of Conservation Science and Research headquarters in Wellington. Right now, though, he is a long way from office towers and tarseal. For this mini-drama is occurring in the uninhabited Auckland Islands, 465 km south of Bluff. East and west of here is nothing but world-encircling sea, storm-tossed much of the time. South is Antarctica.
Gales and his assistant Simon Childer house have come to this spot Ender by Island, at the northern end of the Auckland group to locate and capture five rather special female sea lions. Each is carrying a set of three instruments: a radio transmitter sending signals to a French tracking satellite (from which the sea lion’s position can be determined), a time-depth recorder collecting data on each of the sea lion’s dives and a VHF radio transmitter (enabling scientists to locate the animal on land). The devices were glued to their backs two months earlier, in July.
Ten minutes have elapsed since the dart injected the sea lion with the sedative Hypnoval. She has moved about 20 metres towards the shade of the rata from the more open shrubby patch where she had been dreamily suckling her pup. Already she is looking groggy, but Gales decides to wait another ten minutes before moving in.
His veterinary training has taught him to be cautious when it comes to sedating and anaesthetising sea lions. He needs the animals to be unconscious before he can recover the precious instruments, but will not risk administering a knockout dose by injection with the dart syringe. In the first place, there is the problem of estimating the animal’s weight, and thus the dosage. It would be easy to give a lethal overdose. Next, the sea lion might make a run for the water before the anaesthetic took effect and Sea lions apparently sitting fairly close after a month of separation, when she said, ‘Ooh, that was nice,’ at a gentle caress on her neck. ‘What was nice?’ asked Martin, and they turned to be confronted by the bewhiskered jowls of a huge sea lion that had crept right up behind them.”
Underwater, sea lion curiosity and playfulness becomes even more uninhibited. Photographer and natural history writer Kim Westerskov says they are the most playful of marine mammals, even more so than dolphins. “They do barrel rolls, swim upside down, play games of tag, and face certain death by drowning. Finally, there could be nasty side effects for the animal, not least a monstrous hangover.
So the approach is to give the sedative first, net the animal, then administer a gas anaesthetic a safer procedure altogether. My job, as a volunteer, is to carry the anaesthetic equipment and oxygen bottle-30 kg all up to the side of the animal once netted. At the very minimum, three people are needed for the task. Sea lions are large, carnivorous animals, with impressive teeth and a mean temper if riled. They are not to be trifled with.
Yet having said that, they are remarkably tolerant of humans. Navy doctor Simon Mitchell, who worked with New Zealand zoologist Martin Cawthorn on sea lions in the 1980s, says that the pups, in particular, are insatiably curious, and will climb all over you if you let them. “Once you get the scent of the pups on your clothes,” he says “you can crawl right through the colony among the adults, and, although you have to be wary of some of the bulls, they will basically accept you.”
That acceptance can turn into unwanted attention. Says Mitchell: “One time, Martin arranged for his wife to visit him after we had been down there for a while. They were generally just goof around. At Enderby there can be dozens at a time in the water with you.
“On land, it’s all roaring, charging and baring of teeth. I think the young males have testosterone poisoning from an early age. But when you’re in the water, away from their turf, they see you as a playmate.”
Marine biologist Roger Grace agrees. In the late 1980s, he accompanied National Geographic photographer David Doubilet on an expedition that visited Ernest Island, near the south-eastern corner of Stewart Island.
One of the objectives was to secure good photographs of sea lions under water, but getting pictures proved to be more difficult than they had expected. Although more than a dozen young males were using a sandy beach there as a haul-out area, they were active in the water only at dawn and dusk. “We spent days trying to coax them into the water at times when the light was bright enough for underwater photography, and got chased all around the beach and up trees by the larger males for our efforts,” Grace says. “On the last day, in desperation, I crawled out of the water barking like a dog towards one of the group. He showed some interest in me, and I backed down to the water with him chasing me in a half-hearted way. Once I reached the water, I did have some misgivings. I could no longer run away, and he was a lot faster than me. But my fears proved groundless. In the water, the sea lion turned into a puppy and just wanted to play. The others saw that he was having fun, and all came to join in. They nibbled at our legs and arms, fins and cameras. And David got his pictures.”
Sea lions do not reserve their playful instincts for humans alone. According to Ramari Stewart, who has spent much time in the subantarctic observing southern right whales, one particular whale used to make the same approach to a cove on Campbell Island every day, dragging a large strand of kelp with it. “All the young sea lions would dive in and set off in pursuit as soon as the whale appeared. Some got on its back, but the whale didn’t approve, and would lift its tail flukes and force them to slide off. Another whale did not seem to mind the hitchhikers, and would let them ride.”
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Ten Minutes is up for our sea lion .We locate her in the forest by picking up her radio signal and following the beeps as they grow stronger. Although drowsy with the sedative, she is still capable of movement. The next step is to net her. We have two nets, custom-made for the job. They are the size of whitebait scoop nets, but made of much tougher materials. A hole at the head end allows the snout of the animal to protrude.
Gales and Childerhouse circle around the sea lion. I stand back, anaesthetic gear and oxygen bottle at the ready. The animal senses danger, and roars a warning while standing her ground. The pup scarpers, but will not go far. Its mother bolts in another direction, only to find the sky darkening above her as the net is brought down.Ten Minutes is up for our sea lion. We locate her in the forest by picking up her radio signal and following the beeps as they grow stronger. Although drowsy with the sedative, she is still capable of movement. The next step is to net her. We have two nets, custom-made for the job. They are the size of whitebait scoop nets, but made of much tougher materials. A hole at the head end allows the snout of the animal to protrude.
She struggles, but her struggling only takes her deeper into the net. When her head reaches the end, she is still for a moment. At a word from Gales, Childerhouse dives on her enmeshed head and upper body while Gales gets his arms around her foreflippers and the mid-body.
So far, so good. Now for the anaesthetic. I whip open the case, turn on the gas (isoflurane, which Gales says is a “Rolls Royce anaesthetic” used in hospitals nothing but the best for his animals!) and dial up maximum oxygen flow. They lift the sea lion’s head, and I thrust a rubber mask over her protruding snout. Curiously, the smell of her is more redolent of the earth than of the sea. It is a pleasant animal smell.
We wait for the sea lion to suck in a breath. Underwater, sea lions can hold their breath for ten minutes or more, but after a chase on land we can expect her to take a breath within 30 seconds, and she does, followed by another. Within two minutes she is away with the mermaids. And snoring like a buzz saw.
The New Zealand sea lion, Phocarctos hookeri, is endemic to New Zealand waters. It was named after Sir Joseph Hooker, a scientist on the 1840 British Antarctic Expedition, which called at the Auckland Islands. (Port Ross, the islands’ main anchorage and site of an abortive attempt at human settlement, was named after the expedition leader, Sir James Clark Ross.)
With a total population estimated at between 10,000 and 15,000, it is the least common of the world’s five sea lion species. Its distribution is restricted, too. Most New Zealand sea lions live in and around the Auckland Islands, and 95 per cent of the breeding occurs on Enderby Island and two smaller islands. Because the species has fewer than five main breeding grounds, it is classed as “threatened” a designation which takes no account of population size.
Apart from a handful of sea lion births recorded from Stewart Island, the breeding record on mainland New Zealand in recent times was a blank until Christmas 1993, when a lone female gave birth to a pup at Taieri Mouth, south of Dunedin the first recorded mainland birth in post-European times.
Now, increasing numbers of sub-adult males are turning up on Otago beaches the vanguard, perhaps, of a mainland comeback by a mammal that was once widely, if thinly, distributed around the whole New Zealand coast. Four centuries ago, sea lions virtually disappeared from the mainland hunted out by Maori. Bones at archaeological sites as far north as Houhora tell the story.
Since the 1970s, sea lions have been seen at Otago Peninsula and Catlins beaches in small numbers, about 60 individuals in both locations. Victory Beach and Papanui Beach are the favoured haul-out sites on Otago Peninsula; Surat Bay and Cannibal Bay, south of Nugget Point, are the Catlins strongholds. Almost all of the animals are sub-adult males. Only a handful are females, so it could be some years before breeding colonies are re-established on the mainland. As a species, New Zealand sea lions are making a much slower comeback on the mainland than New Zealand fur seals, which in some areas are increasing in range and numbers at a rate of 10-15 per cent per year.
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Captured Sea Lion , breathing comfortably with eyes shut, is oblivious to the next crucial stage of the experiment. The net is off her, revealing the electronic devices arranged in a line on her back (see foldout). They were glued on to a backing of wetsuit material that, in turn, was cemented to the animal’s furry coat. Gales slices each device from its backing material, which will remain harmlessly on the sea lion till she moults in April.
The instruments worth $8000 a set have to be able to withstand the rough and tumble of sea lion life. During their two months of attachment they are rolled on, knocked against tree branches and rocks and otherwise maltreated. We examine them for wear and tear. Some of the protective rubber on one of the radio antennae has worn away, exposing the wire underneath, but the epoxy resin casing on the transmitters carries only a few superficial scratches. This sea lion has done her job for science. She will not be bothered again.
We pack up the gear and withdraw to look for her pup, a male. He has looped back more or less to where we first found the pair. He is part of the experiment, too, for he carried a VHF transmitter on his back, so that the researchers had an extra clue as to where his mother might be. Weighing about 40 k he is easily netted, and does not need to be sedated while the transmitter is removed. Although only nine months old, he is nevertheless a muscular ball of energy, and it takes a firm grip to keep his foreflippers still.
Adult male sea lions are of no use in this sort of experiment. They disperse too widely, and the electronic gear would almost certainly never be seen again. Females tend to stay in the same general area, and, in any case, they are the more important part of the population, since only a minority of males participate in breeding.
Sea lion research remote, difficult, expensive research is being driven by apprehension over the species’ future in the face of the accidental drowning of scores of sea lions each year in trawl nets.
Sea lions are highly inquisitive creatures. Any sea lion within sight or earshot of a net full of squid (one of their major food items) being winched up by a trawler is bound to investigate. Many become entangled, flopping maimed or dead on the deck of the fishing vessel. Others become trapped in the nets while they are diving for food.
Unfortunately for the sea lions, the Auckland Islands lie at the centre of a fishery known as SQU6T, which occupies 80,000 square kilometres of New Zealand’s subantarctic zone.
The first sea lion deaths were reported in 1978, when a foreign research vessel accidentally killed 10 sea lions in 58 trawls.
Conservationists began ringing alarm bells when the sea lion bycatch continued through successive seasons. In 1982, the Minister of Fisheries declared an exclusion zone of 12 nautical miles’ radius for squid trawlers around the Auckland Islands. In 1993, this zone was upgraded to a marine mammal sanctuary.
But the deaths did not stop. In the 1990 season, the bycatch was calculated at 148. (Data is extrapolated from the reports of fisheries observers on a percentage of boats. Although all boats are supposed to report seal deaths, somehow those with observers aboard always report more.) Given the size of the population and the reproductive rate, conservation scientists concluded that the species could not handle annual losses on this scale.
More than half the fatalities were female, and, more often than not, they were feeding pups. If a lactating pregnant female dies, you can immediately subtract three from the population.
In 1993, a bycatch limit was agreed to by the Ministers of Fisheries and Conservation, in consultation with industry and non-governmental groups. Under the terms of the agreement, when the limit is reached, the minister can close the fishery.
The limit for the 1997 season, which began in January-February and goes through to May or June, was set at 73. By late March, however, more than 100 sea lions had died, and the fishery was closed.
The squid fishery involves over 40 large boats and 2000 crew. The 30,000 tonnes of squid quota allowed to be taken in the area annually has a value of $50 million. This year, only half the quota tonnage was caught before the axe fell.
The fishing industry is naturally unhappy with the decision, and says the bycatch limit is too conservative. John Pfahlert, executive director of the Fishing Industry Board, believes that many more sea lions (300-plus) could be caught without greatly slowing the 10 per cent annual population growth which the board claims is occurring around the Auckland Islands. The Department of Conservation disputes this claim, saying that three decades of pup counts on Enderby Island suggest that the population is static.
The data which Nick Gales and other researchers are producing should not only establish the true status of the sea lion population, but also indicate where sea lions are likely to be feeding in any particular month. With this knowledge, it may prove possible for trawlers and sea lions to keep out of each other’s way.
Even if they can’t, adjustments to gear (escape hatches in the nets) and fishing methods (minimising net time at the surface) may help to reduce the by catch.
It is certainly in the interest of the fishing companies to co-operate in sea lion conservation. This season they stand to lose millions as a result of the closure of the fishery. Given the pressure from environmental groups for a much wider fishing exclusion zone around the Auckland Islands, they could suffer even greater losses in the future.
It is two o’clock , and we have safely retrieved one of five sets of instruments. We noted that the anaesthetised animal awoke after 30 minutes, and was soon reunited with her pup. Now the transmitter from a second female is beeping. We locate the animal not 200 metres from where the first one was caught. We catch her, but miss the pup. No matter; it will keep for another day.
Meanwhile, Gales has locked on to a signal from a third female. She, too, is ashore, though some distance away, judging from the faintness of the beeps. We can hardly believe our luck. We plod upwards through the rata forest pursuing her. It’s hard work wrestling sea lions, but when the subantarctic sun shines on you, you make the most of it. An hour later, a third set of instruments is in the bag.
Within the electronic circuitry of this female’s time-depth recorder, as with the others, is a record of up to 7000 dives—data never before obtained at this time of year. Summer diving data i had already revealed that most sea lion dives are to depths of less than 200 metres and take four or five minutes. A maximum time of 12.1 minutes was recorded. Dive patterns are typically U-shaped and flat-bottomed. That is, the animals swim directly to a target depth—almost always the ocean floor—where they spend the bulk of the time. They average 7.5 dives an hour, with just a few minutes’ breather between dives. No wonder they “blob out” while ashore.
Although sea lion lungs are not much larger than our own, theirs are much more efficient. Whereas we exchange only 10 per cent of our lung capacity with each breath, sea lions exchange 40 per cent.
Like humans, seals and sea lions store oxygen by binding it to haemoglobin in the blood and myoglobin in muscle. But their blood volumes are relatively greater than ours (15 per cent of body mass compared with half that for humans), and they have more myoglobin as well, so they can store a lot more oxygen than we can.
Their resting heart rate is high (60-90 beats per minute), but when diving this slows to perhaps 10 beats per minute. During long dives, blood circulation to non-essential parts of the body is shut down, and eventually it may flow to just the heart, lungs, and brain.
Comparing the time-depth data across different species of eared seals, Gales and a colleague, Rob Mattlin, have concluded that New Zealand sea lions dive deeper than any other species, and stay submerged longer, although true seals can stay down much longer than any sea lion.
Ashore, sea lions often wander deep into the forest on Enderby Island and the main Auckland Island. On Enderby they commonly traverse the belt of rata forest, which is up to a kilometre wide, and end up on the hummocky tundra-like vegetation on the island’s flat summit. However, the animals mate and give birth on the beach.
Breeding occurs over summer. Bulls hold territories from late November, and females give birth to a single eight-kilogram pup in December-January. Up to 480 pups are produced at the Sandy Bay colony alone.
It is a hurly-burly experience for the pups, with bulls belligerent and females trying to get out of their way. After a couple of months, the pups, still suckling, move away from the beaches with their mothers, taking up residence on the grassy flats above the sand, or moving deeper into the forest.
On the more southerly Campbell Island, 290 kilometres away, things happen a little differently. Ramari Stewart reports that on Campbell there is an excess of adolescent males, which constantly harass females trying to give birth if they stay near the beach. To avoid them, the females escape into the scrub, or through that up to the high tussock.
“Some give birth right up on the highest point of the island, at 550 metres,” she says.
A week to ten days after giving birth, the female comes on heat, and will usually leave her pup and consort with one of the beachmaster bulls before going out to sea and feeding for a few days. She then adopts a pattern of spending a day or two with the pup, followed by a few days’ feeding at sea.
The pups gradually work their way down towards the beach, where they form creche groups. They are suckled for up to ten months.
When she returns from the sea, the mother calls to her pup with a cow-like mooing; the pup’s response is a lambish bleat. Stewart recalls that the mother of a pup which died near the weather station called for it for the next two-and a-half weeks.
Once the pups reach the beach, adolescent males may try to shepherd them, practising their harem control skills. Young males fight on the beach at all times of the year, challenging one another in order to progress up the hierarchy that culminates in the old be achmasters, which dominate the sections of beach frequented by the breeding females. Even when they are little more than pups, some of the males are much more obstinate than others, and Stewart comments that you can soon pick which ones will become dominant.
She says that, as a frequent occupant of the beach, she herself was adopted by one young male as part of his putative harem, and he became very possessive of her. It is often these aggressive sub-adult males (“SAMs,” in the lingo of the researchers) that get into trouble with fishermen.
“They will challenge a fisher man on the back of a trawler from the water, and sometimes climb up the slip and chase crewmen about the deck. Fishermen don’t take kindly to this sort of behaviour, but if they get out of sight, the sea lion will usually return to the sea quite quickly,” Stewart says.
Researchers agree that you can’t take sea lion bonhomie for granted. Simon Mitchell still bears the scar from when he was bowled over and bitten by a young male while tagging a pup that belonged in its “harem.
“Kim Westerskov had an unpleasant encounter with a young male during a dive at Enderby Island. In an otherwise playful session, the animal grabbed Westerskov’s head in its mouth and held on. “We hung there motionless, and all the while I was thinking, I hope its idea of play doesn’t overlap with my idea of pain. After a few minutes, another diver appeared, and the sea lion released me and went to investigate the newcomer. My wetsuit hood has the holes to prove it!”
Safety on a place as remote as the Auckland Islands is of paramount importance. You need to be well provisioned, careful with cooking and heating equipment (the main Enderby but was accidentally burned down in 1993), maintain a radio link and, above all, watch your step. Our medical kit contains five different kinds of antibiotics in case anyone is bitten by a sea lion.
Last century, people here were more concerned with clubbing sea lions than side-stepping them.
The first attempt at settlement on the islands involved a group of about 40 Maori who set out from the Chatham Islands in 1842 with some 20 Moriori slaves, and settled at Port Ross. It was tough going. Crops did poorly, although there was sufficient protein at hand in the form of pigs (released by the islands’ discoverer, Abraham Bristow, a whaling captain, in 1809), as well as sea lions, ducks and sea birds.
There are still pigs on the main Auckland Island. Their rootings on the forest floor are conspicuous, and in the winter months they resort to eating seaweed.
Between Bristow’s visit and the arrival of the Maori, numerous sealing gangs decimated the seals and sea lions of the subantarctic islands. The superior coats of New Zealand fur seals made them the preferred species, but by 1815 they were scarce, and the hunters switched to sea lions until they, too, were severely depleted, probably during the 1820s.
In 1849, the English whaling company Samuel Enderby and Sons established a shore station at Port Ross. It proved to be the least successful and shortest-lived British colony of all time, and was disbanded after just two years and nine months. Only one whale came into Port Ross during that time. Now the whales are making a dramatic comeback. A DoC expedition last winter counted 96 southern right whales in the sheltered waters of Port Ross at the height of the breeding season.
The Maori settlers lasted longer than the Europeans did, but an inhospitable climate, poor soils and isolation forced them out in 1856. For both Maori and whalers, Enderby Island was regarded as the warmest and least cloudy place to be in the Auckland Islands—a picnic spot.
The castaway era followed. Three ships were wrecked in the 1860s, including the famous General Grant, and at least five more came to grief over the next 50 years. The stories of castaway privation and valour are legendary (see “Wild Splendout;” New Zealand Geographic, Issue 8).
In Les Naufrages (translated into English as Wrecked on a Reef), the French-born F. E. Raynal describes 20 months spent on the islands in 1864. Sea lions were common at that time—indeed, they formed the bulk of the sailors’ diet—and the small party became so familiar with them that the author included many observations about the animals in his book (see sidebar, page 100).
In the 1890s, a few hardy farmers had a crack at making a living from cattle, sheep and goats, but pulled out after 15 years. Cattle and rabbits survived on Enderby until the early 1990s, when DoC removed them for the sake of the island’s plants, the sea lions (pups were getting trapped in rabbit holes and dying), and ecological integrity.
No one lives here now. These islands enjoy the highest level of protection as a national reserve. Visitors may land at only a few designated sites, and at a rate of no more than 600 a year.
The third female has kept us walking for 20 minutes through the rata. It is mostly open under the forest canopy, a woodland criss-crossed with sea lion and yellow-eyed penguin tracks. While we wait for the sedative to work on this animal, we hear another mother and pup approaching. They call alternately, a mixture of bleat and bark, and pass close to us using a well-worn route.
On land, sea lions look a bit like bears; indeed the females used to be known as “sea bears.” But their dumpy gait and long periods of lethargy give little clue to the balletic skills they exercise beneath the waves. Divers alone witness their grace and speed, and appreciate their true aquatic nature.
Eventually, we capture the third female, and, because this location is so far from our camp and a long way to come next day, we track down the pup and recover his equipment, too. It is dim in the forest by the time we head back to Sandy Bay. Dusk is coming, although at these latitudes the day only slowly submits to night.
Out on the coastal turf, we pass a mob of more than 20 sea lions lying quietly on a bouldery shore. To our amazement, we spot a set of instruments on the back of one of them. With hundreds of animals hauled out around these shores, and many of them hidden in shrubbery or the forest, the chances of stumbling on a “tagged” animal are microscopic.
It is getting late, but Gales decides we ought to try to capture her. He readies the blowpipe syringe and moves gingerly amongst the group. Some of the animals challenge him with full-throated roars, but he knows their limits the boundary between bluff and belligerence.
Childerhouse and I shepherd the darted female away from the water, where she would be in danger while sedated. She co-operates. There is no sign of her pup. Presumably, she recently returned from a foraging trip with a belly full of squid, octopus and fish, and would soon be seeking her hungry pup.
Dusk is well advanced before we have her instruments in the bag. Before heading home along the cliff edge, we stash the heavy anaesthetic gear and the nets in the bushes, ready for use the next day on the fifth and last animal co-opted for this mid-year experiment.
We are tired, but elated. Five days has been allowed for the recovery of the instruments, but we have done four-fifths of the job in just seven hours.
We walk along in silent contemplation, treading carefully in case there are sea lions asleep in the tussocks.
It is dark when we reach the but at Sandy Bay. Nothing much has changed for the sea lions at this bachelor pad since early this afternoon. They lie above the high tide mark, snoozing into the night, although there are a few newcomers amongst them. You can tell because their coats, still wet, are glossy in the faint night light.
Above the swish of wave on sand, we hear a yellow-eyed penguin greeting its mate. It is late in the day for penguins to be calling. But then, it is also late for sea lion scientists to be getting home.
We will sleep 10 hours tonight. Tomorrow, we will go out again among the lions, the pride of the southern seas.