Seals – On the Rebound
Despite being hunted to the edge of extinction in the 19th century, New Zealand fur seals seem to be making a modest recovery. Although the animals are still sparse around most of the North Island, several South Island rookeries are increasing in size, making some fishers nervous at the prospect of increasing competition from these efficient predators. Many, however, are entranced by the lithe, playful animals-and regard seals as a great asset to our coastal wildlife.
As I step from the helicopter and the thud and draught of its blades soften, an awful stench sweeps over me. It’s like being in a piggery, with the accompanying squeals and grunts. But here, on the wild Open Bay Islands 5 km off the coast of South Westland, there are no pigs, nor ever have been. But there are seals—plenty of them—and although none are in view, there is no escaping their presence.
As I cart my gear to the hut, a 150 kg mountain of fur lunges out of the undergrowth at me, mouth agape and barking. Startled, I take several rapid steps backwards, keeping a nervous eye on the animal’s sharp canines.
Hugh Best, a Department of Conservation scientist who has been studying the seals of the Open Bay Islands since 1990, comes to my rescue. “Lucky he’s only little,” he says, using his seal pole to slap the animal on his fore flipper and send him barrelling off into the bush. Seals consider the high part of the island, where the but is, to be “poor real estate,” Best explains. “Only the weakest, lowest-ranking males live here.” I make a mental note: If this one is a wimp, better be very careful around a testosterone-pumped one.
New Zealand fur seals are our commonest native marine mammal, and are distributed around the whole coast of New Zealand and the subantarctic islands. A geographically and genetically distinct population also exists on small islands and coastal stretches of southern Australia.
Total fur seal numbers are thought to be between 50,000 and 80,000—probably 5 to 10 per cent of the number two centuries ago. With the exception of several open seasons, sealing has been outlawed since 1894.
There are two Open Bay Islands: Taumaka and Popotai. I have landed on Taumaka, the larger and more easterly of the pair. During the Pleistocene period, when sea levels were lower, the Open Bay Islands were dumping grounds for debris from an enormous glacier which carved through the limestone bedrock of the West Coast. Today, atop those rocky remnants a friable peat soil supports a tangle of predominantly kiekie scrub fringed by a dark green border of hebe shrubbery.
In the absence of people and rodents, wildlife thrives here, and the islands make an ideal nesting site for the Fiordland crested penguin.
The seal rookery is positioned on the lee side, away from sou’west storms, and has an extensive offshore reef that takes the brunt of any bad weather from the north. There are numerous deep channels, ideal as pup play-pens, and the feeding grounds of the continental shelf are close by.
Down at the rookery, a north-westerly is driving in from the Tasman Sea, freshening the fetid air. At first, the seals seem jittery about me being there, but then settle. I take care not to startle them, because a panicked animal can ignite an explosive chain reaction across the rookery, with the potential to cause injury to larger animals and death to pups crushed in the resulting stampede.
After a few days among them, I begin to think their greatest cause for irritation is my singing—a device I adopt to warn them that I am coming. I find that a steady and well signalled approach is often rewarded with an encounter so close that at times I can smell their fishy breath and hear stomach rumbles. On these occasions I use my bamboo seal pole to scratch them beneath the chin. The seal lifts its snout, thrusts out its jaw to make better contact with the pole and lets out a long muffled sigh of enjoyment.
Even though there is always a busy hum around the colony, everything seems to be played out in slow motion. “Territories are maintained by a series of intimidating glances from the dominant male,” explains Best. “Most challenges are repelled by bouts of staring and posturing, where the objective is to psyche out, bluff and dominate by threat.”
Ultimately, however, a bull will have to fight to win a territory. These gladiatorial bouts occur from mid to late November, when males build their empires. From the safety of a high rock platform, I watch such a fight unfold.
An intruder defiantly enters another male’s territory and is rushed by the owner of the territory. A brief period of manoeuvring for positional and tactical advantage precedes combat. Both seals pull their heads back and inflate their chests into battering rams, then pound into each other. A shuddering impact vibrates through their bodies as they clash.
Again and again, they lunge and recoil. The incumbent destabilises his opponent, but his advantage is short-lived as a mistimed rush causes him to lose his balance. A rapid twist and lift by the challenger gives the latter the upper hand. He lands a crashing blow on the side of the resident’s head. Dazed, the defender lifts himself to meet another attack, but buckles under the force of the blow.
On his neck a marbled red-and-white gash glistens. The wound is as long as my hand, and a couple of centimetres deep. His chest deflates. He looks defeated. Another blow. And another. Pinned to the ground, he starts squealing. The bashing continues, but during a brief reprieve he manages to get away. As he retreats to the sanctuary of the sea, every neighbouring territory-holder gets in a lick as he passes.
A bull may reign over his territory for up to 70 days, depending on his fighting ability, experience and stamina. He will go without food and water the entire time.
“The more experienced animals stay out at sea for as long as possible,” says Best. “They have a good idea when the peak mating period is, and time their coming to shore accordingly. On their first visit to the rookery they may run through the mating area, yowling submissively as they go. Often the same animal will come back a couple of hours later and get into a fight with one of the resident males. The purpose of the initial sortie was probably to have a quick scout to see who they might be able to topple.”
Fighting is tiring and disruptive. If a male spends all his time fighting he will have little energy left for mating. In some ways, the big territorial males are like community constables. Their presence keeps things orderly, and if there are disputes between neighbours the big males will step in to settle them. When there is a lot of fighting in a neighbourhood it normally means the pecking order has not been resolved, and dominance is being regularly challenged.
The formula males use to calculate the appeal of a territory is simple: more females equals more desirable. Females are slightly choosier, selecting from an assortment of features. Preferred sites usually have shady spots beside boulders and rocks, easy access to the sea and the option of shelter or exposure to prevailing winds. “The insulating efficiency of the seals’ underfur and blubber makes it difficult for them to dissipate metabolic heat,” explains Best. “Fur seals don’t pant. To cool off on hot, calm days they must get into the water or find shade.”
Squelching along seal and penguin trails, Best and I crawl under the kiekie in search of an old sealers’ hut. The but was only recently rediscovered—by a researcher trying to escape the unwanted attention of a particularly hostile seal. I am surprised by its small size. It is barely wide enough for me stretch out and lie across, but six to eight men would have shared this shelter. It is in poor repair. Stone slabs lie scattered on the ground and all signs of the roof have disappeared.
Sealing in New Zealand had its origins in the convict trade. British shipping companies employed to carry miscreants to Australia were searching for a return cargo to supply their markets in Canton and Macao. These Asian markets were paying a premium for seal pelts and could supply tea, spices and silk to be onsold in Europe. The first confirmed sealing gang on our shores was dropped off at Luncheon Cove in Dusky Sound in 1792 by the convict carrier and whaler Britannia. The first haul of skins taken from the Open Bay Islands was probably between 1803 and 1806.
In the early days, the density of seals was so great that a gang could base themselves at a single rookery for anything from six weeks to six months, and effectively wipe out all the seals in that location. As seal numbers plummeted, sealers were forced to become more mobile. Using a whaling skiff, a gang of six to eight men would row up and down the coastline picking off seals as they went. This technique continued to be used through the 1820s and 1830s, but for much lower returns. By 1876, commercial sealing had virtually ceased, and the few seals that had survived the 80-year carnage were given legal protection.
Sitting in the hut, I think about the hard life of the sealers. Best has told me about gangs which were marooned and about the dangers of landing a longboat on this exposed coast. “One gang of 10 men was stuck here for four years, surviving on a diet of fish and the occasional fur seal. At one point they managed to sail their leaking boat to the mainland, but conditions there were little better. They found an old whaleboat, but after making it and their existing vessel seaworthy, they were thwarted on the eve of their departure by a storm that destroyed both boats. Demoralised, five men sailed back to Taumaka in a sealskin canoe, still hoping for rescue, but 10 months later they returned to the mainland to build another boat. Using only an adze and a drawing knife, they cut 80 half-inch planks. Just as they were about to start construction they were rescued.”
I was propped up against the seal-watching hide, dozing in the sun, when Best called out: “There. Look. Just beside that ledge. The one that’s sniffing her tail. I think she’s about to give birth.”
Through blurry eyes I saw the animal Best was referring to. She was lying flat and straining forwards, with her hind flippers into the air. “Final delivery usually lasts a few minutes,” said Best. “Can you see the pup’s head?” At that moment the pup slithered on to the sun-heated rocks. Wet with amnion, it quivered, lifted its head and tried to shake off the sticky fluid from its fur.
Bleating pathetically, it pulled itself up the rocks, found its mother’s fore flipper, then followed the line of her body to her front nipple where it began suckling.
“The mother will not leave her pup until it can recognise her voice, which usually takes a few days,” Best said. “In about eight days she will become sexually receptive for a period of around 24 hours.”
I was still getting over the birth, and Best was talking about mating! “The territory holder will go up to her each day to see if she is ready to mate. For the first few days she will act very aggressively towards him and won’t let him approach. But in a little over a week she will begin moving strangely, in a jerky manner, and will act almost submissively. Mating usually lasts 15 to 20 minutes. She lets him know when she has had enough by sinking her teeth into his chest.”
Fur seal cows have a 12-month breeding cycle, but their gestation period is only nine months. After conception, there is a delayed implantation of the blastocyst (a small cluster of fertilised cells), which lies dormant for three months. If the female’s condition is good, the blastocyst is implanted and true pregnancy begins around March. A female seal’s timing is so regular, and her habits so predictable, that she will give birth within one or two days of the date, and within 20 m of the location, that she pupped the previous year.
Pups remain close to the site they were last with their mother. This has obvious survival benefits because, other than an occasional call, a female which has been at sea feeding makes no attempt to locate her pup when she returns. Sedentary pups survive better than ones that roam. As pups grows older they become more adventurous, but they still stay close to the mother’s departure point.
Early next morning I watched a pair of juvenile males chase each other up and down the sparkling channels. Eventually they bring their dispute ashore. A few metres away a female, with pup at her side, yawns, lifts her head to the sun and closes her eyes. Light sparkles on her whiskers.
A fur seal’s whiskers grow to half a metre in length and hold the key to its hunting success. Experiments have shown that seals have little problem catching fish when their eyes are covered, but seals whose whiskers are covered go hungry. Whiskers function like miniature seismographs, detecting vibrations associated with water disturbed by swimming prey. The whiskers are thought to be so sensitive that a seal can home in on a fish 180 m away.
Until the 1960s, little was known about the diet of fur seals. Scientists at that time were asked to evaluate claims from fishers that seals were depleting commercial fish stocks. They concluded that fur seals were feeding principally on non-commercial species such as squid and barracouta, and that they posed no threat to the fishing industry. The situation is slightly different today, given the addition of deep-water species such as hold to the catch list, and fishers regard seals with, at best, grudging suspicion; at worst, outright hostility.
Most of the time, seals catch and swallow their prey without returning to the surface. However, if a seal catches a large fish it will bring it to the surface. I once saw this happen in Deep Cove, at the head of Doubtful Sound, in Fiordland. I was watching some seals, and saw one thrashing around vigorously. As I drew closer, I saw it had a large fish in its mouth. Fur seals do not have the necessary dentition to slice or crush their food. What they do have are large canines that are good for grabbing and holding prey. They break their food up by generating huge rotational force then flicking their heads back, which snaps the fish in two. The seal I was watching broke its prey into several swallowable portions.
Best has been observing and recording numbers of New Zealand fur seals at three West Coast locations since 1990. His research was motivated by concerns over high mortality in fur seals in 1989-90. The seal by-catch on hold fishing boats was the highest recorded at that time, with many animals found washed up between Hokitika and Karamea. Some of the dead animals had net marks or crush injuries consistent with being caught in a net. Most were small, probably yearlings, and Ministry of Agriculture and Fisheries scientists observed that many looked thin, as if starved.
Best believes that high by-catch in the West Coast hold fishery is related to climatic patterns: “There was a La Nina event in 1988-89 which brought about an increase in sea temperatures off the West Coast in 1989-90. The rise in sea temperatures probably had a major affect on the distribution and availability of the cold-water fish prey taken by fur seals. It is likely that these fish moved into deeper water or further south to stay within their preferred operating temperature.
“Smaller seals can’t dive as deep as larger seals, so if the fish are staying deeper, then these animals are going to go hungry.”
In the early and mid 1990s, El Nino climatic conditions prevailed, bringing cooler sea temperatures, abundance of food and strong pup production. However, when La Nina conditions reappeared from mid 1998 to mid 2001, predictably there was a marked fall in the numbers of pups in 1999-2001.
Since 1989, fur seal by-catch in the hold fishery off the West Coast has been highest when sea-surface temperatures have been warmer than normal, as a result of La Nina conditions. During 1989, ’90, ’96, ’99 and 2000 (La Nina conditions) the mean annual by-catch was 799, compared with 229 in 1991-95, when cooler El Nirio conditions prevailed.
About half the West Coast by-catch each year have been males. Best considers that the loss of these animals is unlikely to have an adverse affect on the size of West Coast seal populations. The loss of females has a more serious impact, especially as this mortality comes on top of the loss of pup production during La Nina events. “Loss of pup production leads to a shortfall of recruits for the breeding population several years later. The ongoing loss of cows as by-catch is likely to inhibit the recovery of breeding populations from La Nina- induced setbacks.”
Despite 11 years of observations, Best feels he lacks sufficient data to identify an overall trend for the West Coast fur-seal population. The effect of periodic La Nina events on pup production and survival masks the underlying long-term population trend, he says. Pup numbers fell dramatically in the 1999-2000 breeding seasons to about half the levels of 19921998, and were also lower than normal in 2001. In 1999-2000, pup weights were also much lighter than average, and survival to the end of the first year of life was probably half the usual rate. Low pup condition and low pup survival indicate the mothers had difficulty obtaining enough food to raise their young successfully.
While the West Coast fur-seal population has not grown over the past decade, populations in some other parts of New Zealand have increased. There have been substantial increases on the Otago Peninsula, and numbers along the rest of the South Island east coast seem to be increasing as well. There also appears to have been an increase at the Bounty Islands, the country’s largest known rookery.
Even so, the total population today is tiny compared to its former size. Historian Rhys Richards, who has worked through the 19th-century shipping and marketing records, estimates the former total as somewhere between 1.5 and 2 million fur seals.
“The slaughter by the early sealers was very rapid,” he says, “especially in the five or six seasons from 1804 to 1810, and mainly through preying upon sub-adult males resting at the Antipodes Islands. During a subsequent short revival in the 1820s, sealers hunted the remainder to near extinction.”
Ian Smith, an anthropologist from Otago University, considers that focusing on the numbers is less instructive than comparing the former range of the fur seal with what it is today. After excavating Maori middens in 50 sites around the country, Smith has identified probable seal rookeries throughout mainland New Zealand as far north as Spirits Bay.
“Before humans arrived, virtually all potential breeding sites in the country were occupied,” explains Smith. “Then, with the arrival of Maori, suddenly fur seals were being hunted, and within 100 to 200 years they disappeared from the North Island.”
At present, Cape Palliser, in the Wairarapa, is the most northerly breeding colony, but as seal numbers increase in the south Smith expects the animals to migrate northwards, reestablishing colonies in the sites they formerly occupied.
Seals provoke a range of reactions, which tend to depend on which side of the fisheries fence you sit. At a family gathering in Christchurch, when I explained that I was working on a seal story one of my relatives, a teacher and artist, enthused, “Ah, they are so cute!” Minutes later, another relative, a West Coast accountant, said, “Shoot the lot of them!
They’re nothing but smelly, thieving pests.”
Michael Hart, head of science and research at the Seafood Industry Council, concedes that emotions run high on both sides of the argument. “The council’s position is that seals are a protected animal, and we have obligations to avoid interfering with them,” he says. “But I’m sure that in the back of many fishermen’s minds is the thought: ‘If the seal population is expanding, why do they need protecting.”‘
Peter Stevens, former editor of Seafood New Zealand, supported this sentiment in an editorial about the costs of protecting fur seals when he said, “Like them or hate them, the decisions about managing their numbers are unavoidable and not too far distant . . . [If they continue enjoying protection] it is easy to see them reaching plague proportions.”
Paul Steere, CEO of NZ King Salmon, the country’s largest salmon-farming operation, based in the Marlborough Sounds, has more reason than most to be frustrated with seals. He estimates that they are costing his company around $2 million per year. “At one of our farms last year we lost around 8 per cent of our stocks that we can attribute directly to seals,” he says. “Seals are damaging in two ways: they catch and kill the fish and they also scare the hell out of them, which reduces growth rates and has a direct impact on fish welfare. When we started farming here there were no seals, but by 1995 we counted at least 80 seals during the winter months, and now there are four times that number.”
Seals are now present year-round, with numbers lowest during summer, when most animals return to the breeding rookeries. On the salmon farms they demonstrate their natural territoriality, and are losing their fear of people. In some cases, seals have been aggressive towards workers, snapping at and sometimes charging them.
“This is a worrying trend,” says Steere. “We don’t want our staff to get hurt, so we are trying to be proactive in solving the problem. We have tried using `scrammers’—underwater pinging devices that are supposed to repel seals. Initially there is an effect, but the seals get used to the devices and learn to ignore them.”
In an attempt to protect staff and stock, last year King Salmon took the drastic step of relocating seals to the West Coast and to Kaikoura. Within two weeks, half of the animals had returned to the farms, and a few made the 300 km journey in less than two days. Even so, Steere considered the relocations a success: “If they stay away for 10 days it is worth it for us, and it gives the salmon some respite.”
Earlier this year DoC stopped King Salmon relocating seals because of concerns over the impact relocation might have on the animals.
Ian West, Science Manager (Marine and Freshwater) for the Department of Conservation, says that relocating seals can never be more than partially effective. “All the work that has been done in Tasmania on transporting seals tells us that they come back in about three weeks. They can cover 200 km a day quite happily. Seals are like dogs—they learn. You fill the dinner bowl and they are going to turn up. The only way salmon farms are going to solve their problem is to use nets to stop seals getting into the farms.”
Steere agrees, but says that protecting the farms is not as simple as it sounds. “We are on our fourth generation of predator net, and have invested upwards of $3 million on the problem. Initially, we looked at protecting the whole farm with perimeter netting hanging to the sea floor, but now we are looking at having each cage surrounded by nets. But seals are very intelligent, so it is only a matter of time before they find their way in.”
While the fishing industry gnashes its teeth over fish losses to seals, the tourism industry is cashing in on the increasing seal numbers. Fiona Black, of Monarch Wildlife Cruises and Tours, on the Otago Harbour, says seals are proving popular with visitors. “The albatrosses at Taiaroa Head are our main attraction, but we find that people actually enjoy the seals more I think it is because they are mammals, and people relate better to mammals than to birds. In 1983, when we first started running tours to the albatross colony, there were no seals. The first pups were born in 1986-87. This year we counted 120 pups.”
Amid the range of opinions and reactions regarding seals, there are a few things most people agree on. The seals’ breeding range is growing. There is an increase in numbers along the east coast of the South Island. And the present population is only a fraction of what it was in prehuman times.
There appears to be a measure of good faith between both the fishing industry and conservation groups, and a desire to coexist. Paul Steere sums up the situation well when he says, “We appreciate that we are farming in the seals’ environment. We accept that we have to spend the money to put in protective measures. We do not want to harm the seals. We just want to protect our farms. On the other hand, there should be reasonable seal-management practices to make coexistence possible.”
Seal numbers are recovering from the 19th-century slaughter, but they have a long way to go. For now, the pendulum has swung in favour of seal protection. For the foreseeable future, the signs tell us we’re going to see more of their sleek black forms in our coastal waters.