Smithsonian.com

The winged albatross. Image courtesy of Flickr user AntarcticBoy

Weather changes not just from season to season, but also from year to year. Where I live in Minnesota, we had only a few days of frost before the year’s end, and January, normally the coldest month of the year, was relatively balmy. But in another year we might have days on end of sub-zero weather during the winter. It is hard for a person to detect climate change at this scale, even though global temperature measurements clearly show that the planet has warmed.

But every now and then something comes along that demonstrates a longer term trend that we can see and measure more directly. For instance, the USDA recently released a new version of its “Plant Hardiness Zone Map.” If you are a gardener in the United States, you probably already know about this map; its zones are used to determine what kinds of plants can be grown outdoors in your area, the estimated dates of the last killing frost in the spring and the first killing frost in the fall. This is at least the second time in my memory that this map has been redrawn with all the zones moved to the north, reflecting a warming planet in a way that every gardener can observe and understand.

Not all global climate changes are simple warming, however. Global warming causes changes in ocean and atmospheric circulation as well. Westerly winds in the southern Pacific Ocean have shifted south towards the pole and have become more intense. A recent study in Science shows that the foraging patterns of breeding Wandering Albatross (Diomedea exulans) on the Crozet Islands has been changed by global warming in a way that seems to benefit them now, but that will likely harm them in the future.

Albatross are members of the bird order Procellariiformes, also known as the “tubenoses” because of the tube-like “nostrils” on their beaks. There are about 170 species of this kind of bird, including the petrels, shearwaters, storm petrels, diving petrels, and albatrosses. It is commonly said that the ocean is the last great frontier on earth, and this is probably true. It should not come as a surprise, then, that the Procellariiformes are among the “last great frontiers” of birding and bird research. Since the tubenoses spend almost all of their time at sea, they are hard to study. They come to land only to breed, and even then, usually on remote islands. They are so committed to being in the air over the ocean or floating on the surface of the sea that most members of this order are unable to walk at all. One group of tubenoses has the capacity to shoot a stream of noxious liquid (from its gut) at potential predators, which is an interesting adaptation to being unable to stand up and peck at intruders attempting to eat one’s egg or chick. (See this post for more information on tubenoses and a review of an excellent recent book on the tubenoses of North America.)

Life-long mated pairs of albatross settle in a nesting area during breeding season to lay and incubate eggs, hatch them and care for the young. The nesting sites are communal, so it is impossible for a pair of nesting birds to leave their egg or chick alone while they go out to find food—fellow albatross in the same colony view unguarded eggs or chicks as free snacks. The demand for food increases as the chick grows and requires more and more seafood every day, but the time available for foraging remains at 50 percent of normal because the two parents have to split the duty of guarding the nest and looking for food. In addition, dozens or perhaps hundreds of albatross from a given colony are foraging in the same general area, because they are all tending to nests at the same time. This probably diminishes the total amount of food that is available.

For all these reasons, foraging during nesting is a stress point in the life history of albatross. The birds forage by soaring around over the ocean, using wind as their main form of propulsion, literally sniffing out food sources (they have excellent smelling abilities). Therefore, the pattern of oceanic winds should matter a lot to their survival, especially during breeding season.

Which brings us back to changes in wind patterns due to global warming. The study by Henri Weimerskirch, Maite Louzao, Sophie de Grissac and Karine Delord is destined to become a classic because it touches on a sequence of logically connected observations to tell a compelling story. For my part, I’m going to use this in a classroom to demonstrate interesting science at my next opportunity. Let’s go over it step by step.

Albatross breeding is clearly difficult, and failure is likely common. One indicator of this is the fact that wandering albatross lay only one egg per season. Most coastal and terrestrial birds lay more than one, and in many species the number they lay varies from year to year depending on conditions. If wandering albatross lay only one egg, ever, there is a sort of underlying biological expectation of a low success rate.

For most birds, size matters. Within the normal range for a species, individual birds grow larger when conditions are good, and those birds do better in periods of difficulty because a large body stores more reserves and provides for more effective competition with other birds. A bird can grow large and bring lots of food back to the nest only if foraging is good, and the amount of food a bird obtains in a day is a combination of time (how long one forages) and the amount of food available in the environment.

The amount of food an albatross can obtain depends in part on the total area of the ocean that is searched each day, which in turn depends on how fast the bird flies. Since the albatross soars on the wind most of the time, this means that everything depends on factors such as the speed and direction of the wind. The study we are looking at today combines all of these things in an elegant exposé of the link between climate and the difficult job of producing baby albatrosses.

The wandering albatross travel enormous distances from their breeding grounds, often going more than 1,000 miles before returning to the nest to relieve their mate from guard duty. Males forage more widely and more to the south than females, who prefer northern waters. During this time, the birds use the wind as their primary form of locomotion. The researchers have shown that the winds in this region have increased in strength by a measurable amount, owing to shifts related to global warming. The average wind speed has gone up by about 10 percent from the 1990s to the present day. This allows the birds to move from foraging area to foraging area more swiftly than otherwise possible.

The total amount of time it takes both male and female albatross to complete a full journey of a given distance has decreased by between 20 percent and 40 percent from the 1990s to the present, and the speed at which the birds are observed to fly has gone up about the same for females, though the observed speed increase for males is not statistically significant. This is direct evidence that the amount of time spent foraging is less under present conditions than it was in the recent past, and it can be inferred that this is caused by the correlated increases in wind speed.

During the same period of time, the birds have gotten bigger. In 1990 the average female was about 7,500 grams and by 2010 females were about 8,500 grams. Males increased by about the same percentage, going from the mid-9,000 range to about 10,500 grams. These differences in mass are not reflected in the overall dimensions of the bird, just their weight. This indicates that during periods when the birds are on average smaller, many are underfed.

Breeding success for albatross varies considerably. The chance of successfully launching a baby albatross from the nest for the 350 pairs studied ranges from about 50 percent to just over 80 percent depending on the year (I’m leaving out one really bad year when the success rate was only 25 percent). During the past 40 years, over which it is thought the wind patterns have changed as described above, the “moving average” of breeding success (taking a few years together into account to dampen natural variation) has changed from about 65 percent to about 75 percent. These birds indeed seem to be benefiting from changes in wind pattern caused by global warming.

Most changes in weather, patterns of wind and rain and other effects of global warming are negative, as any review of the literature on this topic over the past decade will show. The benefits being experienced by these birds is unusual. But it may also be temporary. The researchers who produced this result say that the shift of winds towards the poles that brought higher energy patterns to these islands is likely to continue. As wind speeds increase, the benefit the birds will receive will at first level off then start to decrease, as overly windy conditions are bad for the albatross. The shift of westerly winds to the south of the islands will probably decrease the viability of foraging over the next few decades because it will make it easier for the birds to get to places with lower quality forage and thus decrease the rate of obtaining food. So, if the current changes in wind patterns are a gravy train for the Crozet Island wandering albatross, the train may eventually leave the station without them.

Weimerskirch, H., Louzao, M., de Grissac, S., & Delord, K. (2012). Changes in Wind Pattern Alter Albatross Distribution and Life-History Traits Science, 335 (6065), 211-214 DOI: 10.1126/science.1210270

Orcinus orca. Image by Flickr user *christopher*

When I was a kid, I saw a photograph in an old Life magazine of a man standing on the ice somewhere in the Arctic, and a killer whale breaking trough the ice, much of the whale’s body out of the water, a very short distance from the man. The whale was so close to the man that it was hard to say if the wincing expression on his face was due to being splashed with cold seawater or the thought that he was about to be ruthlessly mauled and eaten by the most vicious and dangerous creature on Earth.

Those were the days, of course, when we called these big sea mammals “killer whales” instead of “orcas,” a term many people use now to help the animals’ reputation and enhance conservation efforts. In the old days we knew that if you were anywhere near the ocean a killer whale would thrust through the ice and grab you and eat you. Later we learned that killer whales eat only fish and are never a threat to humans. Somewhere in there was the film Free Willy, which I never saw but assume showed these large members of the dolphin family to be good guys instead of bad guys.

It is now the 21st century, however, and we have a more sophisticated view of wildlife and animal behavior. It is no longer necessary to protect the reputations of predators in order to convince people to appreciate them for what they are, and it is fairly rare these days (though not yet rare enough) to see conservation policy based on fear rather than science.

Meanwhile, knowledge of Orcinus orca dietary behavior is increasing, and the behavior turns out to be quite complex. For instance, killer whales in the Northwest coastal regions are in fact mainly fish eaters, but migratory whales that move in and out of that region tend to eat mammals. The following three unusual principles seem to be emerging:

1. Any given group of these whales specializes in a type of food, and a group doesn’t change its dietary pattern very much over time.
2. There is a wide range of potential specializations, ranging from fish to seals or sea lions to smaller whales to larger whales.
3. Different social groups can be found in the same waters at the same time, with different specializations for feeding.

The killer whales that live in the far north, mostly in the Arctic Circle, have been studied the least of all, so their dietary preferences and overall relationship to the rest of the ecosystem is not as well known as it is for other groups. Also, with global warming, it appears that killer whales are either newly colonizing some of the waters in these northern regions, or spending more time there than before. To sum up: Killer whales have complex, variable behavior that cannot be assumed without direct observations; a large region in which they live lacks intensive research; and things may be changing in that region. Thus the significance of a very interesting paper, just out, by Steven H. Ferguson, Jeff W. Higdon and Kristin H. Westdal.

The researchers employed a method called “Traditional Ecological Knowledge” to characterize the diet and behavior of killer whales in Nunavut, Canada. People who live in a region often know a lot about its environment. This is, of course, not always true. For instance, here in Minnesota, the bears are all Ursus americanus, also known as “black bears.” But their fur color varies a lot, so there are whitish ones, brownish ones and even blond ones. A lot of Minnesotans think we have two kind of bears here, black and brown, incorrectly assuming that a black bear that is brown is Ursus arctos, the brown bear. The point is, I would not trust a randomly chosen Minnesotan to be able to accurately list which members of the order Carnivora live in their own state, let alone to describe the animals’ diet or behavior.

When I lived with the Efe Pygmies in the Ituri Forest of Congo, the opposite was true. The Efe really knew the animals and their behaviors. It took some patience and expertise (as a trained anthropologist) on my part to get through some of the cultural confusion. For instance, every person has a “totemic” animal, an animal into which deceased ancestors can manifest now and then, and some of these animals were imaginary. But I quickly learned to identify the imaginary animals because in every case there is only one of them, and it lived in a particular spot out in the forest somewhere. Otherwise, however, the Efe had what I would regard as perfect taxonomic knowledge and extensive behavioral knowledge of all of the mammals and birds in in the rain forests in which they lived.

In one instance, the Efe talked about a chameleon that made a “woo woo woo” noise during the full moon, but that was otherwise impossible to find. We scientists, however, knew that chameleons were always silent. There are no vocalizing species of chameleons, so this was impossible. Of course, we would hear this animal every full moon, but assumed it was some kind of as yet unidentified frog or something. Maybe even a bird.

Then, one day, Western scientists discovered this African chameleon that said “woo woo woo” during the full moon. Turns out the Efe were right all along, and we had egg on our scientific faces.

The study at hand points out that killer whale preferences for prey are largely unknown in the eastern Canadian Arctic. To remedy this, the researchers surveyed native Inuit people to develop an understanding of Inuit Traditional Ecological Knowledge (TEK) regarding killer whale feeding ecology. They conducted more than 100 interviews in 11 Nunavut communities in the Kivalliq and Qikiqtaaluk regions during the period from 2007 to 2010.

The Inuit knew about what the whales ate, how they hunted and captured prey, how the prey responded to the whales and when and where predation events occurred. The information provided by the Inuit agreed with the available published literature and expanded on it. For instance, both the TEK and the published information agreed that killer whales sometimes eat only certain parts of their prey, especially in the case of large whales. Also, small groups of killer whales, acting cooperatively, would attack large whales. The Inuit data suggested that the whales took any and all sea mammals, and in this area, either did not eat fish or hardly did so (it had not been observed).

From the published paper:

By combining TEK and scientific approaches we provide a more holistic view of killer whale predation in the eastern Canadian Arctic relevant to management and policy. Continuing the long-term relationship between scientists and hunters will provide for successful knowledge integration and has resulted in considerable improvement in understanding of killer whale ecology relevant to management of prey species. Combining scientists and Inuit knowledge will assist in northerners adapting to the restructuring of the Arctic marine ecosystem associated with warming and loss of sea ice.

In the distant past, scientists often ignored and even made fun of the knowledge of indigenous people. But we now recognize that people who live off the land for generations know more than researchers will discover with years of investigation. If you ask, “should we ignore the vast knowledge of the native people of the Canadian Arctic” the only good answer is, “No, we’ll have Nunavut.”

Ferguson, S., Higdon, J., & Westdal, K. (2012). Prey items and predation behavior of killer whales (Orcinus orca) in Nunavut, Canada based on Inuit hunter interviews Aquatic Biosystems, 8 (1) DOI: 10.1186/2046-9063-8-3

Editor’s Note: Thanks to our readers for catching an error in our original headline. Inuit is indeed the plural form — not Inuits. The error has been fixed. Thanks — BW

A good eye will spot the black-marble jawfish next to the mimic octopus's arm (Credit: Godehard Kopp)

The mimic octopus (Thaumoctopus mimicus) has the uncanny ability to make itself look like more dangerous creatures, such as lionfish, sea snakes and soles. The octopus does this with its distinctive color pattern and ability to adjust its shape and behavior (see this earlier blog post on the octopus for a video in which it mimics a flatfish). But now the mimic has a mimicker of its own, scientists report in the journal Coral Reefs.

Godehard Kopp  of the University of Gottingen in Germany was filming a mimic octopus during a diving trip to Indonesia last July when he spotted a companion–a small fish that followed the octopus for several minutes, always sticking close to the octopus’s arms. Kopp has some good observational skills, because the fish’s color and banding looks incredibly similar to that of the octopus.

Kopp sent his video (see below) to two marine scientists at the California Academy of Sciences who identified the fish as a black-marble jawfish (Stalix cf. histrio). The three write:

Jawfish are poor swimmers and usually spend their entire adult lives very close to burrows in the sand, to where they quickly retreat, tail first, upon sight of any potential predator….[In Kopp's video and photos], the Black-Marble Jawfish seems to have found a safe way to move around in the open. The Mimic Octopus looks so much like its poisonous models that it is relatively safe from predation, even when swimming in the open, and by mimicking the octopus’ arms, the Jawfish seems to also gain protection.

This might at first glance appear to be a case in which the fish evolved its coloring to gain protection by associating with the octopus, but the scientists don’t think that’s likely. The jawfish can be found from Japan to Australia, but the octopus lives only in the region around Indonesia and Malaysia. They contend that this is a case of “opportunistic mimicry,” in which the fish is taking advantage of a happy coincidence.

A great white shark off the coast of South Africa (courtesy of flickr user hermanusbackpackers)

Every year in False Bay, South Africa, great white sharks congregate as Cape fur seal pups are weaned. Seals feed offshore, swimming out together in groups of five to 20. They spend a few days foraging, depending on each other to protect against shark attacks. The sharks, though, have many advantages, such as big bodies and sharp teeth. And they can use the power of physics–specifically, water optics–to aid in their attacks, say scientists in a new study in Marine Biology Research.

Seal vision is best adapted to seeing through the shallow coastal waters where the animals spend most of their time. When Cape fur seals watch out for sharks, they do so by lying at the surface, looking down into the depths. This is good enough to find bright objects below them, but great white sharks, despite the name, have dark grey backs that camouflage well against the dark reef floor near the island where the seals live. In low light conditions, a seal won’t be able to see a shark until it’s about 2.6 meters away.

Shark vision is different from seal vision. No one has determined directly how well a great white sees, but studies of its eyes have shown that the shark has a high rod-to-cone ratio in its retina, which should give it good vision in low light conditions, like those in early morning when they most often hunt. And when they look up to the surface where the seals swim, they see an easy-to-spot dark flippered body silhouetted by the sun.

The researchers observed sharks in False Bay as they leaped out of the water in their attacks on seals and calculated the maximum speed reached, about 35 kilometers per hour (22 mph). To reach those speeds, the scientists further calculated, the shark would have to start its attack from at least 7 meters away, and the seal would have only a tenth of a second to react. “Stealth and ambush are key elements in the white shark’s predatory strategy,” said study co-author Neil Hammerschlag of the University of Miami.

Real-world observations seem to match up with these calculations. Most shark attacks occur over a water depth range of 7 to 31 meters. And great whites are more successful in their attacks during low-light conditions; 55 percent of their attacks are successful during those times versus less than 40 percent in bright light.

But if a great white doesn’t make a kill in that first strike, its chance of success decreases with longer it tries to catch his dinner. Young Cape fur seals can reverse direction in a much smaller distance than their shark attacker needs, which lets them take evasive action, leaping away from the shark’s jaws before it can take a second bite.

Bottlenose dolphins are good swimmers (courtesy of flickr user Willy Volk)

Human females often find late pregnancy to be a bit of a drag, as they waddle about trying to accommodate a big baby belly, but they can take comfort in knowing that dolphins probably have it worse. Pregnancy for them really is a drag, physics-wise, and they may find it harder to catch food or avoid becoming a predator’s meal, according to a new study in the Journal of Experimental Biology.

Researchers from the University of California at Santa Cruz and the Southwest Fisheries Science Center studied two female bottlenose dolphins at Dolphin Quest Hawaii, measuring and weighing them and diving with them, recording them as they swam, starting from a week or so before each gave birth and continuing their observations for two years. Pregnancy, they found, had serious consequences for movement through water.

Pregnant females may appear as streamlined as their non-pregnant counterparts, perhaps a bit fatter, but their bellies increase their frontal surface area by 51 percent, which greatly increases drag. They also can’t sweep their tails as far as when they’re not pregnant, so they have to change their gait, sweeping faster to compensate. During pregnancy, dolphins also increase their stores of fat to prepare for lactation after they give birth, but the fat makes them more buoyant and they require more energy to dive. As a result of all of these changes, pregnant females swim slower. “Two to three meters per second is a comfortable speed for most bottlenose dolphins,” says the study’s lead author, Shawn Noren of U.C. Santa Cruz, “but these pregnant animals did not feel comfortable going beyond that.”

The dolphins in the study were captive animals, so their lack of speed was no more than an inconvenience. But for dolphins in the wild, the inability to swim fast could be deadly, the scientists say. Dolphins’ main predators–sharks and orcas–can easily swim at speeds greater than the maximum reached by the pregnant animals. And a dolphin’s pod may be little help if all their friends have swum away. “Ultimately,” the scientists write,” the results of this study support the notion that reproduction is a costly endeavour that may increase energetic expenditure, increase risk of predation and decrease longevity.”