A Superlative Penguin
The Antipodes Islands are in the middle of nowhere. More precisely, they are three and a half days of vomiting southeast of my home in Dunedin, New Zealand. I am the sort of person who gets motion sickness on escalators, and as I lay strapped into my bunk on the Breaksea Girl, I asked myself over and over, “Why am I doing this?”
The answer was penguins. Of the world’s sixteen species, all have been studied in detail except one. I was after the last, the erect-crested penguin. This penguin owes its anonymity more to its location than to any lack of cuteness or scientific interest. Erect-crested penguins breed on the Antipodes and on a similarly isolated group of islands nearly 200 miles to the north, the Bounty Islands. Both are home to little more than seabirds, seals, and shipwrecks.
Erect-crested penguins are, quite simply, the most striking of penguins. Upright parallel combs of blonde feathers sit incongruously above their eyes, like Marilyn Monroe’s eyebrows on steroids, lending the penguins a feminine beauty. But what drew me most to these birds was that they were rumored to exhibit an extremely bizarre behavior. There had been only two prior attempts to study these penguins scientifically—one conducted about thirty years ago, late in the breeding season, and a more recent one lasting a mere five days, during the period of egg laying. The authors of this last study asserted, remarkably, that these penguins, which lay two eggs, deliberately eject the first egg from the nest soon after it is laid.
It was another twist to one of the stranger stories in the animal kingdom. The erect-crested penguin is one of five species known as crested penguins. All five lay two eggs but rear only one chick. Furthermore, in contrast to all other birds, they lay a second egg that is larger than the first, and it is the chick from the second egg that is most likely to survive. Biologists have long sought the answers to two questions: Why produce two eggs if only one chick can survive? Why is the second egg larger? I was, I told myself with each roll of the boat, in search of answers to such questions as much as I was after the “last” penguin.
Late during the fourth night I heard the anchor being let out, and mercifully, the wild pitching eased. I went up on deck to get my first glimpse of the place my two companions and I would be calling home for the next two months. In the morning gloom, I peered straight out at the 600-foot-high cliff aptly named Perpendicular Head. At its base, huge waves crashed relentlessly. I had never seen a place less likely to offer sanctuary, less likely to be called home.
Fortunately, not all the cliffs that surrounded the island were as high as this, but unfortunately, in the small cove that offered the only reasonable landing site, the waves were as fierce as those that pummeled Perpendicular Head. Despite the apparent proximity of the penguins, which I could make out as groups of dots at the base of the cliffs, at that instant they seemed very far away.
We had no alternative but to choose a much less desirable landing site, at Stella Bay. To call our approach a landing is really to glorify it; it was much more like a controlled crash. Wearing wet suits, Martin Renner (a former student of mine), Dave Houston (a biologist from New Zealand’s Department of Conservation), and I jumped from a dinghy into the freezing water. A wave immediately slammed us into the rocks, cutting open my knee. We grasped kelp to anchor us, so as not to be taken out in the backwash, and clambered over its slimy fronds to the jumble of boulders that constituted the beach. We then had to wade back in and retrieve repeated dinghy-loads of gear that were tossed to us between one wave and the next: packs of clothes, boxes of food, drums of fuel, generators, scientific equipment, and wood for mending a hut constructed on the island about a century earlier to shelter castaways. By the time we had finished, we were all cut and bruised. After tossing us a box of sandwiches, the captain of the Breaksea Girl waved good-bye and steamed off to the northwest, leaving the three of us—the entire human population of the Antipodes Islands—in an enveloping drizzle.
Next we had to get our gear up a 70-foot-high cliff; carry it through waist-high tussock grass, which is just about impossible to walk through without falling over every few steps; and, finally, wade through a bog. It took us two full days of backbreaking work to lug all our supplies up to the hut.
While completing this task, we were able to make our first casual observations of the penguins. Stella Bay is home to a colony of about 300 breeding pairs. At this stage, however, virtually all those present were single males, which typically arrive at the colony a week or more before the females. Why they should do so is not at all clear; it’s not as if they have a swag of boxes and generators to hoist up to their nest sites before getting down to the business of courtship. The classic explanation is that they come early to secure a site before the females get there, but other penguins manage this without the need for the males to arrive so far ahead of the females. It is said that the males use this period to fight like gladiators for nest space, with the victors presumably getting the choicest sites. But we saw little evidence of this; there was hardly any fighting at all.
It would be wrong to assume from this that male erect-crested penguins are not territorial. They will defend their chosen site if they have to, even at their own peril. The biggest fight we observed was between a male fur seal and a male penguin. The fur seal lunged at the penguin on its nest, shook it vigorously, and tossed it about fifteen feet away. With a deep wound to its chest, the penguin made the mistake of returning to attack the big hairy intruder. This time the seal reached down, grabbed the penguin, and shook it so violently that its head came away from its body. To our surprise, the seal—supposedly a fish eater—set about devouring its foe. A quick check of the colony revealed five similar carcasses. This had been no crime of passion but the premeditated act of a serial killer. We envisaged this rogue seal slowly eating his way through the entire Stella Bay colony as the breeding season progressed. Fortunately for the penguins, two days later a group of elephant seals arrived, banishing the much smaller fur seals to the nether regions of the beach, and the carnage stopped.
We chose to study the penguins breeding in Anchorage Bay, in the lee of Perpendicular Head. Our main study colony was situated atop a rock stack, and from a knoll above it we were afforded an unimpeded view of all the nests—the perfect place to make observations. But first we had to measure and mark the penguins so that they could be recognized individually. Penguins really do all look alike.
The birds proved to be remarkably unperturbed by our presence. We set up shop near the colony and began a processing operation. First I would catch a penguin, using a fishnet like those used to land trout. It was a relatively easy task to approach a penguin quietly and let the net fall gently over it, pulling the bird toward me as I did so. I had to be fairly deft with the next bit: grabbing the penguin around the ankles with my left hand and then quickly grasping the back of its neck with my right. These penguins have sturdier bills than most others. The top mandible ends in a vicious hook that is used to grasp fish but that is quite capable of ripping open your arm or any other part of your anatomy within striking distance. I would carry the penguin to Martin and Dave, who would weigh it; place a numbered stainless-steel band on the right flipper; and measure foot, flippers, bill, and crest. I then took a small blood sample from a flipper, and Martin photographed the crest. Finally, I painted both a letter and a number on its back in white enamel so the individual could be recognized from a distance. This was the key to our behavioral study, because it meant that we would never need to handle the penguin again. Each bird could be completely processed in this way in less than five minutes. In all, we marked 271 individuals before beginning to observe the colony continuously throughout the daylight hours.
The first thing we noticed was that not a lot happened. Even after all the females had arrived and most males were paired up, these guys were positively lethargic compared with other penguins I had studied. The most riveting thing to happen during the entire courtship period occurred on the shoreline in front of us.
A big bull elephant seal had been lying there sleeping when another cruised up like a submarine, inflating its huge proboscis and blowing bad breath in a deep growl. Our erstwhile beach companion raised its head and inflated its own nose. The seal in the water caterpillared up the stones, and the two giants faced each other, their bodies bent at right angles, their noses quivering like jelly-filled socks, their mouths wide open. For a while it seemed that they were going to do battle with their breath—the smell must have been lethal at such a point-blank range.
The intruder flung its head at our resident and bit the side of his body with its huge canine teeth. Our man was no slouch in this department either, and he struck back with a vicious blow to the intruder’s back, tearing two parallel, foot-long cuts in its blubber. They continued to trade blows, thumping their chests together and biting each other’s body. It seemed an evenly matched contest—until the resident received three unanswered strikes to his right side. Perceptibly, he changed. The intruder leaned more into him; he arched back further. Inch by inch, the intruder shuffled the resident out to sea. In the surf, our guy put up one last stand: bloody open mouths were held close together, and then a final lunge, a final bite, and it was all over.
Now that was competition. The mating game we were witnessing in the penguin colony was gentle and benign by comparison. I was used to observing the mating behavior of Adélie penguins in Antarctica, where the courtship period is a frenzy of fighting and fornicating. The erect-crested penguins, in contrast, just did not seem to have their hearts in it. They rarely fought, and whereas Adélie pairs copulate every three hours or so, erect-crested partners consummated their relationship only once every thirty hours. The blood samples we had taken revealed that the males had relatively low levels of testosterone, which might have explained their lack of both aggression and libido. But the females, too, were out of sorts. While female Adélie penguins will copulate within minutes of arriving at the colony and pairing up, female erect-crested penguins were likely to reject a male’s initial advances. These penguins seemed to arrive at the colony only half ready to reproduce.
We settled into a routine of observation stints to watch this protracted, if tame, courtship ritual for clues to the penguins’ behavior. After the females had been at the colony for about two weeks, the first eggs were laid. While this signaled an exciting change for us, the penguins were much more blasé: to our surprise, neither mothers nor fathers were inclined to do much about it. Some attempted to incubate halfheartedly, but many simply stood beside the egg and ignored it. Another surprise was that the vast majority of the erect-crested penguins made absolutely no attempt to construct a nest. Other penguins collect stones or grasses to line their nests (except king and emperor penguins, which incubate their single egg on their feet), but these birds were content simply to drop their eggs on bare ground or even on the tops of large rocks, often on steep slopes. Without a decent nest, any knock or bump was likely to send an egg rolling away.
In an experiment we conducted in a nearby colony, we created supernests, surrounding some rudimentary nests with large stones so that the first eggs could not roll away. But these survived no longer than those in control nests or in the main study colony. Although the first eggs remained within the vicinity of the nests, they were neglected: some rolled against the rocks, and many broke, probably after being trod on or pecked at.
We found that about four of every ten first eggs are lost before the second is even laid, but the arrival of the second egg seals the fate of the first. I suspect this is largely for mechanical reasons. The first is not much bigger than a chicken’s egg from a supermarket; the second is nearly twice that size. And while first eggs are pale green, second eggs are white. During the five or six days between the laying of the two eggs, the first one—if it survives that long—gets quite dirty as well. A female that has just laid her second egg responds more strongly to the stimulus of the large, bright white egg and will push it into her brood patch, a feather-free area of vascularized skin on her tummy. She will then attempt to draw in the small first egg, but it is like trying to sit on a football and a tennis ball at the same time—an awkward proposition exacerbated by the eggs’ aspherical shape, which makes them prone to rolling unpredictably. Females seem to find it difficult to get comfortable. They stand up repeatedly, turning around in the nest and trying to adjust the eggs.
Almost inevitably, the smaller of the eggs, being less snug against the female’s body, will be dislodged and will roll away. At least another four of every ten first eggs are lost this way on the very day the second egg is laid. And the longest we observed any first egg to survive was six days after the second appeared. But this was not deliberate rejection, as claimed by earlier researchers. Females tested at a colony about half a mile away readily tried to retrieve and incubate a first egg that had rolled away if we replaced it within a few inches of the nest. The combination of parental neglect, differences in egg size, and poor nests seems to conspire against the prospects of the first eggs.
But simply knowing how first eggs are lost does not explain why the penguins persist in laying two eggs and why the second one gets all the attention. Some have suggested that crested penguins lay two eggs because the first is an insurance policy in case the second, larger one is lost. But for erect-crested penguins, at least, this scenario seems ludicrous: more than 80 percent of these so-called insurance policies are lost before or on the day the second egg is laid, and none of the remainder last for more than a week.
Often when one tries to decipher why animals do what they do, a good place to start is with food. Penguins can be divided into two broad groups: those that feed inshore and those that feed offshore. Crested penguins are of the latter kind, swimming just about as far as their flippers can take them to find food and rush it back to the chick. The costs of finding and transporting food over such distances make it unlikely that these penguins could ever bring back enough food to feed two offspring. So why bother laying two eggs? DNA evidence suggests that the ancestors of crested penguins laid two eggs. However, given the circumstances crested penguins face, surely it would be to the females’ advantage to reduce their clutch size by simply stopping their laying after the first egg.
For whatever reason, erect-crested penguins have a long courtship period of two weeks or more. That means that males and females are ashore, and unable to feed, for an extended period of time. While penguins are quite capable of dieting for phenomenally long periods, when it comes to producing the energy and nutrients needed for egg laying, fasting females must convert their reserves of fat and protein, since they can’t use nutrients derived directly from food. The little work done on this suggests that erect-crested and other crested penguins depend more upon converting their reserves for manufacturing eggs than other penguins do.
Conversion of fats and proteins for egg formation, like most of reproduction, is a hormone- mediated process. Hormones are like chemical postcards that the brain sends around the body to tell it what to do, and it seems crested penguins arrive at the colony with comparatively few of these missives getting delivered to their reproductive system. The synthesis of hormones can be influenced by external events, such as calls made by other penguins or the physical presence of eggs. Indeed, the social stimulation derived from the calling and courting of neighbors in the colony has been shown to hasten the development of eggs in crested penguins.
Our results seemed to confirm the benefits of breeding in a crowd. The size of both first and second eggs tended to increase as the colony filled up and became more boisterous. Very early breeding pairs tended to lose their first egg immediately, suggesting that the adults were not ready to care for it properly. The brood patches of both female and male crested penguins take several days to become fully vascularized and suitable for incubation; work by my students on yellow-eyed penguins, the crested penguins’ closest living relatives, has shown that the presence of an egg stimulates the development of the brood patch.
As I sat atop the knoll, looking down at pairs of penguins hunkered down on and protecting second eggs, while all about lay the abandoned and broken shells of first eggs, it occurred to me that we were asking the wrong questions about their strange breeding behavior. The real question is not why they have two eggs but why they favor the second egg. Had the first egg been at least as likely to produce offspring as the second, it should have been a relatively simple matter to stop there and reduce the clutch to a single egg. But, of course, to take advantage of the better prospects of the second egg meant having a first one, too, no matter how superfluous that might be.
Could it be that the first is really just a primer for the birds’ reproductive system? Had natural selection tilted the balance in favor of the second egg because females were then better able to mobilize their reserves to produce it, and both males and females were better prepared to care for it? If so, then crested penguins have little choice but to lay a first egg even if it has little prospect of producing a surviving offspring. All they can do is reduce its size and the energy they invest in it. To explain why crested penguins favor the second egg, then, is also to explain why they must persist with laying two eggs and why the first is smaller.
Crested penguins’ breeding strategy has served them well enough for millions of years. But recently, in the face of environmental changes being wrought by humans all over the Southern Hemisphere, there are signals that all is not well in the crested penguin world: Major population crashes have been recorded for rockhopper penguins. Fiordland penguins are already among the world’s rarest. Snares penguins seem to be holding their own but are limited to a single breeding area, making them extremely vulnerable to a local catastrophe. Only macaroni penguins (including a subspecies, royal penguins) appear to be in reasonable health. No truly accurate census of erect-crested penguins exists. However, just over a decade ago there were estimates of 110,000 pairs breeding on the Antipodes, while a few years later the population was estimated to be only half that.
My colleagues and I did not have the time or resources to census all the penguin colonies on the Antipodes, but we did survey and count breeding pairs in representative colonies on the main island. Antipodes Island is less than five miles in length and somewhat more than a mile across at its widest point. It is, however, a desperately hard island to traverse. Its cliffs forbid coastal access, leaving the interior—a tussock-covered plateau—as the only feasible route. The going was particularly tough and the results discouraging: our sampling indicated that the size of the various breeding colonies had fallen between 8 and 41 percent since the counts made three years earlier.
Albatrosses are distant cousins of penguins. On the cliffs above the colonies, we encountered nests of the light-mantled sooty albatross; on the plateau, huge wandering albatross chicks sat like white, fluffy lighthouses. Simple economics dictates that albatrosses, too, can never rear more than one of their gargantuan babies and so lay a single egg. However, the albatrosses’ strategy has one major advantage over the penguins’ when environmental changes affect the distribution and abundance of prey: Albatrosses can fly. Penguins, even offshore-feeding penguins, are much more constrained by how far they can go from the colony and are therefore much more susceptible to local perturbations in the ecosystem.
We do not know just where erect-crested penguins go to find fish, but because a chick must be fed frequently after it hatches, parents must be limited to foraging within a radius of less than seventy-five miles from the colony. The crested penguins’ approach to chick provisioning also differs from other penguins’. Whereas in other species the parents take turns getting food for their newly hatched chicks, crested penguins strike a blow for female liberation, with the female being the sole breadwinner for the first two or three weeks, while the male stays at home to look after the chick.
During the period when the eggs are being incubated, erect-crested penguins are likely to travel hundreds of miles on feeding trips that can last upwards of two weeks. The energy demands of fasting through courtship and producing eggs are high, and in other species of penguins, either the male or the female departs immediately for the feeding grounds after egg laying. Not crested penguins. Parents remain together at the nest for up to ten days or so after laying. This baffled us as we continued to monitor the study colony, because only one parent at a time can incubate the egg—and the male, especially, having already gone without food for about a month, must have been starving. Why should he continue to hang around?
When hunger did eventually force the males to leave (after they had lost some 40 percent of their original body weight), we witnessed yet another twist to this tale: neighboring males and unemployed birds—penguins that either had not bred or had failed to breed successfully—went around attacking the females left alone on their nests. The poor females lay prone over their second eggs, flippers spread-eagled, forehead tucked down onto the ground, eyes closed, while the marauders meted out a flurry of blows with their flippers and beaks. In several cases, a female was forced to abandon her nest, and the egg was broken. Could it be that their male partners had remained with them so long after egg laying to guard them?
As our time on the Antipodes drew to a close, I was beginning to see the erect-crested penguins not so much as the last penguins but as the oddball penguins. Instead of answers, we had found mostly more questions. To unravel their story further, it seemed unavoidable that we would need to return. And as I boarded the Breaksea Girl for the journey back to New Zealand, that thought alone was enough to make me ill immediately.
– From: Natural History, 01/11: 46-55