Hedging our bets
In fall, about 21 mammal and bird species worldwide, mostly in northern regions, change their coat or plumage colors from brown to white. White provides camouflage against predators as snow covers the landscape in winter. In spring, these same...
In fall, about 21 mammal and bird species worldwide, mostly in northern regions, change their coat or plumage colors from brown to white. White provides camouflage against predators as snow covers the landscape in winter. In spring, these same animals shed their white colors and return to brown, which provides similar camouflage when next to the brown leaf litter on the ground. Some animals can turn white and some remain brown year round.
Only one or at most a few genes control the ability to change color seasonally. Natural selection is a powerful force determining the abundance of these genes in different environments. In a paper in the March 2 issue of Science, Scott Mills and colleagues show that the probability of turning white in winter increases with longer durations of winter snow cover for Japanese hare, white-tailed jackrabbits, and least and long-tailed weasels. With fewer than 40 days of snow cover, only 20% of the individuals of each species have the genes for turning white. But with more than 160 days of snow cover, over 80% of the populations of each of these species have the genes for turning white. In the broad range of snow cover between 40 and 160 days, the populations contain a roughly even split of winter-white and winter-brown individuals. During periods of snowy winters, white individuals have greater survival and there are more children born the following spring possessing these genes. During stretches of snow-free winters, brown individuals have greater survival and more children. Under these conditions, natural selection preserves both color forms. In order to maintain these species in a warming climate with gradually decreasing snow cover, Mills and colleagues suggest that we must conserve these particular populations with both sets of genes, thereby hedging our bets.
But there could be further complications. When the environment goes through large changes, there is a period of instability when it rapidly switches back and forth between two states (snowy and snow-free winter landscapes following one another, for example). One year there is strong selection against one trait (brown) with selection against the other (white) the following year. This instability in the environment creates corresponding instability in the organism's gene pool. It is important that the population density not drop too low during periods of environmental instability because low survival of the animals with the wrong color, one year after another, could drop the population below the minimum size needed to be viable. Hares and weasels are famous for going through boom and bust cycles every four years or so (see Chapter 14 in my book What Should a Clever Moose Eat?). During their population lows, the fate of these species may depend upon whether snow conditions align by chance with the abundance of the coat color that provides the best camouflage.
As with any good research, answering one question opens up newer and even more interesting ones. Incorporating animal population cycles into the interesting findings of Mills and colleagues seems to be a next step in designing strategies to conserve these species in northern environments.
Who Speaks for the Trees?
“I am the Lorax! I speak for the trees.
I speak for the trees, for the trees have no tongues.”
“I am the Lorax! I speak for the trees.
I speak for the trees, for the trees have no tongues.”
Does Nature have rights that courts of law must consider? If it does, who speaks for Nature in the courts? Recently, both India and New Zealand have responded to these questions by granting personhood status to three rivers, the Ganges and Yamuna in India and the Whanganui in New Zealand. Indigenous peoples in both countries argued that the wellbeing of both the rivers and the people are inseparably linked. Whatever happens to the rivers happens to the people, so if the people have standing in courts of law, so should the rivers.
These actions by the Indian and the New Zealand governments bring to fruition a proposal raised nearly 50 years ago, in 1972, by Christopher Stone in his influential book, Should Trees Have Standing? (republished in 2010 by Oxford University Press). I was an undergraduate geology major at the time of its publication. While I didn’t become an environmental lawyer, this slim volume made me realize that deep social and legal reasoning are equally required to solve environmental problems as are the scientific approaches I was learning in my classes.
Under English and American common law, Stone explains, it is unthinkable for natural objects such as rivers or forests to have legal rights. First, natural objects do not have standing in courts of law: that is, they cannot bring a suit on their own behest. A downstream riparian landowner can bring suit against a polluter upstream, but that suit is brought on the landowner’s behest, not the damage to the river itself. Second, in making a decision on a suit, the court weighs the economic hardships of forcing the polluter to cease against the economic losses of the downstream riparian landowner. The damage to the river’s food web does not weigh in the balance. Finally, the beneficiary of a favorable decision is the downstream landowner, not the riverine food web. This landowner may choose to spend the monetary award from the polluter on restoring the river in the stretch flowing past his or her property, but is not obliged to. In summary, under common law, damage to natural objects has no meaning or standing in and of itself, but only in relation to the economic well-being of a group of citizens who have standing to bring the suit.
The Ganges River near the Lakshman Jhula bridge in Rishikesh, India
Natural objects cannot speak for themselves. Instead, Stone suggests that a group of citizens be granted guardianship status over natural objects. In the case of the rivers in India and New Zealand, the Hindu and Maori peoples have been granted guardianship status over the rivers because their traditions state that the rivers are central to the peoples’ existence: damage to the river also constitutes damage to the people. The guardians in turn have a responsibility to ensure that monetary awards for lawsuits brought on behalf of the rivers are spent on the rivers themselves. Finally, the guardians have the responsibility of monitoring the health and well-being of the rivers. These decisions of the Indian and the New Zealand courts go far beyond the status of natural objects in common law.
Giving legal rights to natural objects is unthinkable for many people. It will remain unthinkable until they value natural ecosystems exclusive of their roles as suppliers of resources and services for economic well-being. It is hard to value a natural ecosystem or a landscape for itself until we think it is worthy of rights. The decisions of the courts in India and in New Zealand are attempts to break this vicious circle. Because of these decisions, we may be on our way to a heightened empathy with natural landscapes and a deeper understanding of our relation to them.
I thank my grandson for help with the Lorax quote.
What should a drunken moose eat?
John Pastor, author of What Should a Clever Moose Eat? reflects on the question: What should a drunken moose eat?
Red, ripe berries and fruits, such as those of mountain ash, cranberries, hawthorns, and apples, are a sure sign of a bountiful harvest at the end of summer, but after a few freezes in autumn these fruits can become deadly to wildlife. The cells of the fruits are broken open as ice crystals form, then melt, then form and melt again during cycles of freezing and thawing. The glucose and other sugars they contain are then released to natural populations of yeasts on the fruit surfaces, which ferment the sugars to ethanol, much like what happens to grapes when they are first crushed to make wine.
Quite often in late September or October, after the first hard frost, I’ve seen flocks of cedar waxwings and robins become inebriated after eating mountain ash berries. Recently, there have been several reports of moose that apparently became drunk after eating too many fermented crabapples in Alaska and piles of fermenting apples in Sweden. Birds weigh only a few ounces, so it shouldn’t take much ethanol to make them drunk. Moose, on the other hand, weigh between 500 and 1200 pounds, so it would take a lot of hard cider to get them inebriated. Petter Kjellander, Professor at the Swedish University of Agricultural Sciences, thinks that it is not possible for a moose to eat enough fermented fruit in one sitting to make it drunk. The moose’s rumen can hold only so much fermented apple mash before it must stop eating and chew its cud. This load of fermented apples probably does not contain enough alcohol to induce inebriation in a large moose, and the three hours it takes to empty a moose’s rumen should be sufficient to cleanse its system of the ingested alcohol. On the other hand, perhaps some moose, like some people, are genetically disposed to an intolerance of alcohol, and so only a small amount might get them intoxicated. The answer to this problem will likely tell us something new about the physiology of moose.
We have peculiar tastes in foods when we sit at a bar too long – witness the varieties of pickled things in typical bar food. Might a drunken moose also have the same tastes? After the yeasts create the ethanol, bacteria turn some of it into acetic acid, otherwise known as vinegar, so apples, crabapples, and berries become pickled while they ferment. Perhaps the combination of fermented and pickled apples stimulates the moose to keep eating far beyond what is good for it.
Salted nuts, chips, and popcorn are ubiquitous wherever alcohol is served, whether in bars or at a Super Bowl party. Do moose have a craving for salt when eating fermented fruit and if so, where can a moose get it? Gary Belovsky and Peter Jordan found that aquatic plants are a major source of salt for many moose in summer and perhaps in early fall when fruits in the uplands are starting to ferment. But once the ponds freeze in late fall, aquatic plants are no longer available. Then, moose are often seen licking the gravel on the sides of roads, presumably for the salt put down by transportation departments to melt the ice. A drunken moose on the side of the road is potentially a great danger to motorists, so beware if you are driving in moose country during late autumn!
And what should a moose do about the hangover the morning after a fermented fruit binge? We can go to the drugstore and pick up some aspirin, but a moose can go to the original source of this universal painkiller. Aspirin is salicylic acid and was originally isolated from the bark of willow in the genus Salix, from which salicylic acid takes its name. Willow twigs are highly preferred foods of moose from fall to spring. By the end of winter, many willows along streams and in bogs look like someone went at them with a machete, but the many moose tracks in the snow tell us the real culprit. I’ve often thought that moose eat the willow bark to stave off the pain of cold weather or crusty snow slashing their shins raw. Perhaps some of these tracks were also made by moose who became drunk by eating berries of mountain ash along the streambank or fermented cranberries in the bog. If so, then the tracks of a drunken moose should wander erratically, like a drunk stumbling home after the bars close. If I snowshoe through a willow bog this winter, I’ll keep an eye out for tracks that may have been made by a stumbling moose. If there are browsed mountain ash berries nearby, then I may be on the track of a drunken moose coping with a hangover.
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