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 telomere is like an aglet. Aglets are those plastic or metal tubular thingies at the end of your shoe laces that keep the end of the shoelace from becoming frayed and facilitate inserting the lace into the eyelet. A telomere is a sequence of base pairs at the end of a chromosome. A chromosome zips apart during cell division so that it can be replicated, and a small number of base pairs typically get lost during replication. This is because the molecular machinery that duplicates the chromosome can’t read through to the end of the strand, so it just skips the last bit. Any meaningful genetic information at the end of the chromosome would be lost or garbled. A nice long telomere at the end of the chromosome allows for multiple duplications without the loss of meaningful information, but over time even the telomere may be lost through attrition, and further replication of that chromosome would be a problem.

There is a system, using the enzyme “telomerase,” that adds base pairs to the telomeres, but there tends to be an imbalance between adding new base pairs by telomerase and losing the base pairs during replication, so in a given individual, new copies of chromosomes may eventually start to have less information than they are supposed to, which leads to cell death or worse—it is thought that this can be a cause of cancer in some cases. Shorter telomeres may mean a shorter lifespan, and longer telomeres a longer lifespan, for a cell line, or more interestingly, for an individual.

That is all pretty well established science, but the numerical details have been somewhat lacking. There has not been a study of a reasonably large sample of organisms in which telomere length was measured early in life, then lifespan measured in each organism, to verify if there is an association between telomere length and how long an individual lives. Until now.

A Zebra Finch. Photograph by Flickr user pixelblume.

A team of researchers from the University of Glasgow and the University of Exeter at Cornwall have just published an article in PNAS called “Telomere length in early life predicts lifespan.” The paper looks at 99 zebra finches in which telomere length was measured on the 25th day of life, and lifespan was measured by keeping the birds in a controlled captive environment until they died. Lifespan for these birds ranged from less than one year to almost 9 years. One can imagine the researchers waiting around for that last bird to die so they could submit the paper.

Telomere length early in life correlated strongly with lifespan of the birds, though there was enough variation in the outcome to suggest that multiple other factors are involved. The researchers conclude that “[a]lthough reduced telomere length has been associated with a number of degenerative diseases in humans, there has been increasing interest in their role in the aging process in otherwise normal individuals. The results of this study clearly show that telomere length early in life is predictive of longevity.”

At this point you are probably wondering if it is possible to add to our existing telomeres and possibly increase lifespan. It is possible that this could actually work, through gene therapy. This has been done in lab mice and other test animals. It is also possible, however, that long telomeres or telomeres lengthened artificially can cause an increased risk of cancer (for as yet unknown reasons). Also, it is not universally true that telomere length decreases during lifespan; in some organisms is seems to increase. One thing can be said about telomere biology at this point: There are many unknowns. Don’t be surprised to hear more interesting research about them over coming months and years.

Heidinger, B., Blount, J., Boner, W., Griffiths, K., Metcalfe, N., & Monaghan, P. (2012). Telomere length in early life predicts lifespan Proceedings of the National Academy of Sciences, 109 (5), 1743-1748 DOI: 10.1073/pnas.1113306109

A cane toad is highly toxic and should not be eaten or even licked. Photo from Wikicommons.

American cane toads (Rhinella marina), native to Central and South America, are an invasive species in Australia. These toads contain a substance called “bufotoxin” that makes a lot of predators ill, sometimes fatally. (Warning: This is very poisonous stuff. Do not even lick a cane toad!)

Australian animals that eat this toad are typically poisoned by it, but one animal, the bluetongue skink (Tiliqua scincoides), appears to be able to eat the toad with few or no ill effects. Or, more exactly, some bluetongue skinks can eat the cane toads, depending on where they live.

Many animals and plants produce complex molecules (like bufotoxin) that have been shaped by natural selection to be toxic to predators. Some of our favorite spices, such as basil, chili peppers and other aromatic plants, owe their culinary properties to these molecular adaptations to herbivory. Only a few mammals produce molecular toxins, but many frogs and toads do.

The bluetongue skink. Note the blue tongue. Photo from Wikicommons.

If a weapon evolves in nature, there is a certain chance that a counter-weapon will also evolve. Many insects that feed on toxic plants have evolved the ability to sequester the poisonous molecules produced by those plants, rendering them harmless to the insect, and in some cases concentrating the undesirable substance in the insect’s own body to be used as a defense against insect-eating animals (usually other insects). Many mammals have enzymes in their digestive tract that detoxify plants that would otherwise be harmful. The evolution of toxicity and the evolution of anti-toxin strategies is considered an arms race between the eaten and the eaters.

So, it would be reasonable to suspect that the bluetongue skink has evolved a physiological mechanism to combat the bufotoxin produced by the cane toads. But it turns out that the explanation for the ability of some skinks to snack on the toxic toads is a little more complicated.

Another invasive species found in Ausralia is the ornamental “mother-of-millions” plant, a Bryophyllum from Madagascar. This plant produces a toxin that is chemically similar to bufotoxin. Why is it chemically similar to bufotoxin? This is probably a coincidence. If you have a large number of animals and plants producing toxins, sometimes there are going to be accidental similarities.

Mother-of-millions plant. Image from Wikicommons.

The mother-of-millions plant is invasive and found in the wild in certain areas of Australia, but it is not common everywhere. Bluetongue skinks that live where mother-of-millions is common appear to have adapted to eating them, and as such posses the ability to neutralize bufotoxin-like molecules. When these skinks encounter cane toads, they eat them without consequence. In fact, the skinks living in these area regularly eat both the mother-of-millions plants and the cane toads.

This research was was carried out by scientists at the Richard Shine Lab at the University of Sidney.

Price-Rees, Samantha J. Gregory P. Brown, Richard Shine, 2012. Interacting Impacts of Invasive Plants and Invasive Toads on Native Lizards. Natural History Editor: Craig W. Benkman. Published online Jan 25, 2012

One of the most interesting large-scale patterns in evolution is parallelism. For example, flight has evolved many times, in parallel, from numerous non-flying organisms; many species of vertebrates that are not fish have evolved swimming, in parallel. One study discovered parallel evolution in body armor among freshwater stickleback fish from numerous saltwater ancestors.

Another interesting thing about evolution, which has only been appreciated in recent decades, is the fact that there is not a simple correspondence between genes and traits. Rarely does one gene determine one trait, and rarely does one trait vary because of one gene. There are dozens of examples of simple gene-trait relationships, many of which were discovered years ago. Because these relationships were relatively easy to find and describe, our textbooks are full of them and our thinking about genetics was for a long time based on them. But this is a little like basing our conception of how all vehicles work by deeply understanding the workings of a toy wagon. The mechanics and engineering of a little red wagon will not help us understand escalators, submarines, or Apollo lunar launch systems. We now think that most genes affect multiple traits and most traits are affected by multiple genes, and that it is all very complex.

A recent study looking at stickleback behavior seems to be an example one gene affecting multiple traits.

Sticklebacks are members of the Gasterosteidae family of fish, with species that live in salt and fresh water. The freshwater sticklebacks evolved from saltwater ancestors who were landlocked less than about 17,000 years ago at many locations across the Northern Hemisphere. For this reason, differences among freshwater and saltwater sticklebacks represent recent and rapid evolution among a well-known group of species and are thus especially interesting to scientists.

Saltwater sticklebacks have up to 36 bony plates associated with a smaller number of sharp spines. These plates and spines protect the fish from predators, but they are costly to produce and maintain. The bony plates require extra calcium, which is rare in some environments, and they restrict the body movements of the fish.

Freshwater sticklebacks tend to have fewer spines and bony plates. Some have a gap in the row of plates (this is called a “partial morph”) while others have only a few plates at the back end of the fish (“low morph”). Fresh water has less calcium than salt water, so this may be an adaptation to a limiting resource. Also, freshwater environments tend to have fewer predators than saltwater environments, so the protective features of the bony plates may be less important in fresh water; perhaps there was relaxed natural selection on this armor, and over time it was lost in many different populations in parallel.

Top: The ninespine stickleback, Pungitus pungitus, is typical of the saltwater form. Bottom: A freshwater form of stickleback with fewer bony plates and fewer spines. Image based on drawings from the Queensland Government Fisheries

In a 2005 study, scientists looked at a gene (Eda) that determines the growth of the bony plate and found that freshwater sticklebacks had a variant of the gene that caused fewer plates to form in those populations. The gene Eda probably serves a regulatory function, so it could determine one of a range of phenotypes from the fully armored saltwater version to the two lesser armored versions found in fresh water. A combination of genetic and population analysis led the researchers to discover that most freshwater sticklebacks in the Northern Hemisphere which exhibit a loss of bony plates do so because they all inherited a variant of Eda that is rare in the original saltwater populations. So the trait evolved in parallel in many lineages, all of which came from different saltwater populations, but it also evolved from a single pre-existing form of the gene. However, it was also found that one or more of the Northern Hemisphere sticklebacks with reduced bony plates got this trait from an entirely different genetic change.

This trait is thus an example of a feature determined by more than one gene, and an example of parallel evolution occurring by more than one means.

A second study just reported at a scientific meeting looks at what seems to be an entirely different question about stickleback evolution. Most sticklebacks form schools, which is a common adaptation among fish, following the principle that there is safety in numbers. But there is one population of freshwater sticklebacks that does not form schools. The sticklebacks of Paxton Lake, in British Columbia, Canada swim around alone most of the time. Rather than forming schools, they hide out in thick vegetation on the bottom of Lake Paxton.

The research team led by Anna Greenwood of the Fred Hutchinson Cancer Research Center in Seattle devised a machine to test for and measure schooling behavior in sticklebacks. This consists of a mobile-like cluster of fake fish which move together as a robotic school in a circle around a large aquarium. When fish from a schooling population of sticklebacks were placed in the water with this machine, they joined the fake fish and swam around with them. When fish from the non-schooling population were placed in the water with this machine, they did not school. These two populations are so closely related that they can interbreed. The researchers tested offspring of the schooling and non-schooling fish to see which behavior each fish would exhibit. As expected, some schooled, and some did not. Once the hybrid fish were sorted out, their genes were examined to see if there was a particular signature that went with schooling versus solitary swimming.

It turns out that the gene that seems to control schooling behavior in these fish is none other than Eda, the same gene that controls the number of bony plates.

So the sticklebacks not only give us a great example of how parallel evolution can arise, but also a great example of a gene affecting more than one trait. But how does that work? The fish that do not develop bony plates also do not develop a fully functioning lateral line. A lateral line is a sense organ many fish have that allows fish to detect movement elsewhere the water. Some predatory fish use the lateral line to find their prey, other fish use the lateral line to detect predators and thus avoid becoming prey, and schooling fish use the lateral line to keep track of the other fish in the school. Apparently, the sticklebacks with the poorly developed lateral lines can’t school because they can’t properly sense the other fish with whom they would need to coordinate their movements.

Sources:

Colosimo, Pamela F., Kim E. Hosemann, Sarita Balabhadra, Guadalupe Villarreal, Jr., Mark Dickson, Jane Grimwood, Jeremy Schmutz, Richard M. Myers, Dolph Schluter, and David M. Kingsley. 2005. Widespread Parallel Evolution in Sticklebacks by Repeated Fixation of Ectodysplasin Alleles Science 25 March 2005: 307 (5717), 1928-1933. [DOI:10.1126/science.1107239]

Pennisi, Elizabeth. 2012. Robotic Fish Point to Schooling Gene. News and Analysis. Science 335(6066):276-277. DOI: 10.1126/science.335.6066.276-b