Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
SAF Archives  search ask the scientists in the classroom cool science
scientists from previous shows
cool careers in science
ask the scientists
PREVIOUS SCIENTISTS

Environment Decade as seen on The Frontiers Decade


q Why is it that when the fungus attacks the sea fans in the Caribbean, it turns them purple? What ideas do scientists have to cure this fungus disease?

A Sea fans have structures known as sclerites. These are calcium carbonate deposits that help make up the skeleton. These sclerites can be clear or pigmented (purple). When the fungus invades the coral tissue, the coral produces a higher percentage of purple sclerites, thus purpling the tissue. We think this is a protective response that sea fans have to limit the spread of the fungus. A cure is not on the horizon. Once we are satisfied that we know the origin, spread and pathogenesis of the infection, we can think about how to interfere with the overall process. We just need to know more about it for now.
Garriet Smith
Science in Paradise, October 1998



q How long have you been doing rescue work with whales off Newfoundland and how many have been successful?

A I first came to Newfoundland many years ago. Back then, whales were still hunted for their meat. Although I spent lots of time on the water in my boat, it was many years before I saw my first whale. What a sight! It was very exciting to see a huge humpback from my little boat. However, it was many years before I became interested in whales as a scientist. My first interest developed because fishermen in Newfoundland would call the university where I work when a whale was in trouble and ask that someone come and help. Because I was an animal behaviorist that worked with wildlife, people in the university would often pass these requests on to me.

In 1978 a fisherman called the university and reported that a humpback whale had been caught in his nets for 3 months. He could not get the animal out; the animal was too weak to get away. No one the fisherman had contacted was willing to help. This request for help was passed on to me. I took some of my students to the scene of the entrapment and figured out how to let the whale free. We successfully released the whale and retrieved the fishing gear. I was very concerned that this was a terrible way to treat a whale, and it was terrible that the fishermen could not find any help. So my students and I conducted a survey to find out how often large whales were accidentally caught in fishing gear. It turned out that this was a frequent occurrence. We tried several agencies that might have helped. The general reaction was "If you are concerned, why don't you help?" That was the basis for the formation of the Whale Entrapment Assistance Program in Newfoundland and Labrador.

Before the program, about 50 percent of large whales died during entrapments. After the program began, only about 10 percent die. Whales that today die in fishing gear are dead when the fishermen find them and they just can't be helped. But most are safely released alive. Since 1978 there have been many hundreds of whales which we have released from fishing gear. Humpbacks are the most common. But in the 18 years of the Entrapment Assistance Program some 11 different species of whales have been released from fishing gear.
Jon Lien
Creatures of the Deep, February 1996



q Will the hawksbill turtles be extinct soon, or will programs like yours save them? Are there laws to protect them and to stop people from killing them for their shell or meat?

A I don't think hawksbill turtles will be going extinct soon, but what is soon? Sea turtles, like hawksbill turtles, have been here swimming in our world's oceans for over 100 million years and through hunting, pollution, and loss of nesting and foraging areas most of the world's sea turtle populations are in serious trouble. This means where once there were 100,000s sea turtles there are now only 1000s alive. Possibly too few to enable the species to survive. I hope that programs like ours will help save the hawksbill turtle and other species. We are working very hard to help the hawksbill turtles at Buck Island Reef NM survive - we protect the nesting females and their nests and hatchlings and hope we are providing a safe coral reef area where young hawksbill turtles can grow to maturity. Here in the United States there are many laws to help protect sea turtles; the most important is the Endangered Species Act under which all sea turtles are protected. Another law which helps to protect sea turtles around the world is CITES, the Convention on International Trade in Endangered Species, which prevents other nations from catching and selling endangered species like hawksbill turtles and exporting or selling these animals or parts of them to the US or other countries. Unfortunately not all nations have signed on and agree to the rules of CITES, it is their choice, we can only provide them with the facts and hope they agree to protect critical species. We all continue to work toward a global protection for all sea turtles species and programs like Scientific American Frontiers "Science in Paradise" are helping.
Zandy Hillis-Starr
Science in Paradise, October 1998



q It seems the Chinese will have a difficult time capturing and breeding the Chinese River Dolphin before the big dam is completed. What do you think are their chances of saving this species?

A Massive habitat alterations are virtually impossible to reverse in any reasonable amount of time. Recent attempts to survey the baiji population resulted in almost no sightings. If researchers can't find them they can't catch them for breeding programs. Qi Qi (pronounced Ji Ji or Chi Chi) is the only baiji in captivity today. Human activities, such as habitat destruction and fishing, are the major reasons why the baiji is endangered. While some people are trying to slow these destructive activities, they have been going on for so long that it is very difficult to change them. Attempts to find and catch some of the few remaining baiji to place them in safe areas have failed so far. It may be too late to save the baiji.

Here is a reference if you'd like to learn more: Baiji: The Yangtze River Dolphin and Other Endangered Animals of China by Zhou Kaiya and Zhang Xingduan. Stone Wall Press, Inc., 1241 30th Street, NW, Washington, DC 20007.
Dan Odell
Dragon Science, November 1995



q When biologists set fire to the plains in Africa, is there any danger of desired animals being harmed?

A Yes. Animals of all sizes are in danger of being harmed by both management induced fire as well as a wild fire. The degree of harm that any fire causes depends primarily on two things: 1. The group of animals and 2. The circumstances under which the fire burns. Generally, the smaller slower moving animals are more susceptible than the larger, faster moving and agile animals. For instance I have seen insects, lizards, snakes, tortoises and rodents either injured or killed by fire, but I have never seen an antelope (e.g. impala, nyala, wildebeest), megaherbivore (e.g. elephant, rhino, hippo) or mammalian predator (e.g. lion, leopard, cheetah) injured. With regard to the circumstances under which the fire burns, those that burn under mild conditions (cool moist days with low wind speeds) resulting in a low intensity fire, provide far greater opportunities for escape that high intensity fires (those burnt on hot dry days and at high wind speeds). Generally, when setting management fires, we err towards the milder conditions and adopt a point source burning strategy (as shown in the video), which emulates the way in which a wild fire is started and minimises the possibility of animals becoming entrapped by the fire.
Pete Goodman
Science Safari, November 1996



q As an ecologist, what is your study of scorpions teaching you about the desert environment generally?

A Scorpions are superb example of a creature adapted for the desert. They allow us to understand how animals can live in such harsh climates. They have a higher heat tolerance than any other creature in North America; they use and lose less water than any other creature; they only need to feed a few times a year to survive. Yet, they maintain populations there are often quite dense

Also, my studies on diet have shown the ecological world about the general importance of omnivory, cannibalism and an interaction called intraguild predation (competing species that also eat one another). Scorpions are cannibalistic, eat almost anything and this really allows them to do well in an environment where food is relatively scarce. Omnivory and cannibalism help many other desert creatures to do well in the desert.
Gary Polis
The Wild West, October 1995



q I realize that there must be laws dealing with your contact with the wildlife and plant life on the Galapagos Islands. What are some of these guidelines, and how do they help or hinder research on the islands?

A The Galapagos National Park Service has a set of regulations that visiting scientists must adhere to. Some have to do with what scientific work is permitted, and you can only do what has been approved for your project by the Park Service. Some have to do with how you live when you are camping; basically you have to leave the site the way you found it. Much of it is common sense for a wilderness area. The most important regulation that scientists must pay attention to involves to danger of transporting organisms between islands. A number of damaging creatures have been introduced to the Galapagos since humans arrived, and we are extremely careful when we move from one island to another to clean all of our equipment, the bottoms of our shoes, the nooks and crannies in our tents, and everything else. If we moved an introduced plant or fire ant or mouse from, say, an island with a town to a pristine wilderness island then that organism and its descendents might have a bad effect on the native biota on the pristine island and that would be terrible.
David Anderson
Voyage to the Galapagos, October 1999



q The show gave us a brief, but balanced overview of the negative and possible positive impacts of ecotourism on the Galapagos Islands. As someone involved in the industry as a guide, and as someone who clearly loves the islands, how do you feel about ecotourism?

A I feel quite strongly that well-controlled ecotourism in the Galapagos benefits the Islands much more than it negatively impacts them. If people are able to visit the Islands and experience their uniqueness first hand, and see for themselves that the animals here are unafraid - indifferent - to man, and yet so vulnerable to us, and have intense and very personal encounters with the beauty and the wildness that is so prevalent and so distinct in this Archipelago, then I know that those people immediately understand the need to save these islands and other wild areas like them for future generations. There are many things that must be improved to properly handle the number of travelers who are now coming to Galapagos - for instance, a better quarantine system for all planes and ships that enter the Archipelago - but I sincerely believe that only if people are able to visit and experience these truly Enchanted Islands will we be able to obtain sufficient world support to save and protect them.
Lynn Fowler
Voyage to the Galapagos, October 1999



q If there is another El Nino event that threatens the marine iguana population on the Galapagos Islands, will you or other scientists try measures to save them (like bringing in seaweed for them to eat)? Or do you think it's better to just let "nature take its course

A We will let nature take its course, because we can not decide what is best for the marine iguanas. Our knowledge about history is so poor, but nature has influenced these creatures for millennia. This is why they are what they are. If we mess with the selective forces of nature, we could entirely mess up this fascinating species. Nature knows better than we do, and if we help the weak animals survive during an El Nino, there will be no chance for the strong ones to propagate their genes. Just imagine marine iguanas would learn to eat on land if we feed them there. They would not be marine iguanas any longer, maybe. Besides all that, the National Park prohibits the feeding of animals, for exactly the reasons given.
Martin Wikelski
Voyage to the Galapagos, October 1999



q If Charles Darwin were visiting the Galapagos Islands with you today, would he see essentially the same islands and biological systems that he saw 165 years ago?

A No, unfortunately, were he visiting the Galapagos today, Charles Darwin would not see the same islands as those found 165 years ago. Although the Ecuadorian government has done an admirable job in protecting the islands from the onslaught of humans, our impact is significant and quite visible; and in my opinion, the Galapagos Islands are still quite endangered. The introduction of alien species, such as rats, goats, dogs and cats, has had disastrous effects on the flora and fauna of the Galapagos. There are many other human-related problems, such as solid waste generation, pollution, and destruction of habitat, which threaten the pristine and fragile ecosystems of the Galapagos. The forces of natural selection are still at work, but the added dimension of human-impact is an ever-present danger.
Sherri Steward
Voyage to the Galapagos, October 1999



q If a rattlesnake is deaf, how does it know to rattle its tail to scare an enemy? How did this behavior develop?

A Let me start with a little general background, and then relate it back to the problem of the rattle. In nature, animals that are poisonous to eat, or that are venomous (like many snakes) are often brightly colored. For example, think of the monarch butterfly which is poisonous to eat, and colored brightly orange and black. Many poisonous insects are brightly colored, like the milkweed beetle, and the blister beetle. Likewise, animals that sting or have venomous bites are often brightly colored, like the velvet ant, the wasp, and the coral snake. Brightly colored visual signals are popular in the animal kingdom as a warning that says "Stay away from me, I'm dangerous." Bright coloration evolves as a warning signal when potential predators learn to associate bright coloration with danger. Imagine a coyote that is bitten by a coral snake and gets very sick. The coyote learns to associate the color of the snake with injury. The next time the coyote encounters a coral snake, it will avoid interacting with the snake, saving itself pain, and saving the snake from harm as well. Clearly, both the coyote and the snake benefit from the snake's coloration. The bright coloration of the coral snake is called "aposematic coloration."

While this is all well and good, being brightly colored has its disadvantages. Imagine being brightly colored like the coral snake, and trying to catch and eat an animal that sees color very well. Some animals rely on cryptic coloration to conceal themselves from their prey. They lie in wait, practically invisible because of the way their coloration blends into their surroundings. When the appropriate prey species blunders by, these ambush foragers burst out of hiding to capture their next meal. The rattlesnake is just such a creature. Rattlesnakes have very cryptic coloring, which hides the snake not only from potential food items, but also from potential predators like hawks, roadrunners, coyotes, and people. The rattlesnake's most typical behavior is to lie motionless, using its coloration to conceal itself, until potential threats pass, or potential food items come within striking distance. Once discovered by a predator, the rattlesnake would clearly benefit by being brightly colored like the coral snake, but such coloration would make it hard for the snake to catch its food.

So, how does the rattlesnake warn away potential predators without giving itself away to potential food items? Natural selection has provided an answer in the rattle. The rattle is a remarkable structure that serves as warning badge that uses auditory signals rather than visual signals. The sound that the rattle makes is every bit as recognizable to predators as the coloration of the coral snake. Predators learn to associate the rattlesnake's buzz with danger. The fact that the rattlesnake can turn the sound on and off at will means that it can stay concealed when necessary, or if required, raise a warning ruckus.

Now, more directly to your question, the rattlesnake doesn't need to hear to know when to rattle. For this system to work, only the predator needs to be able to hear -- it is the perception of the predator that is most important, because only the predator needs to associate the sound with danger. As an interesting side issue, Kingsnakes, which are also deaf, often eat rattlesnakes (hence the name "kingsnake"). Typically, a rattlesnake confronted by a kingsnake does not use its rattle to warn off the kingsnake. Instead, the rattlesnake has a whole separate set of behaviors that are only exhibited when confronted by a kingsnake. This point is related to the second part of your question. How did the early rattlesnakes know to vibrate their tails? Well it turns out that most snakes vibrate their tails when they are agitated. Perhaps you have had the experience of disturbing a snake and having it rapidly vibrate its tail causing a buzzing sound in grass or leaves. Why snakes do this isn't exactly known, perhaps it is just a nervous response, or maybe the snakes get some benefit from making noise when they are agitated (given the above arguments, this shouldn't seem far-fetched). At any rate, tail vibrating seems to be a natural response for snakes. Now, imagine a venomous snake that by some accident of genetics begins to retain dried scales on the tail after shedding. These dried scales may make extra noise when the snake vibrates its tail. Predators learn to avoid these noisy and venomous snakes, and the snakes with noisier tails survive longer to reproduce more than their silent brothers and sisters. In the language of evolution, suppose a mutation arises that increases the amount of noise that the tail makes when vibrated, now natural selection acts on that mutation for millions of years, and the end result is the familiar rattle we see today. The exact steps in the evolution of the rattle are forever lost in history (unless we get really lucky and find fossils of early rattle structure), nevertheless, the evolution of the rattle must have occurred in approximately this way.
Steven Beaupre
The Wild West, October 1995






 

Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.