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

Wonders of the World as seen on The Frontiers Decade


q Why are some ocean creatures luminous in the dark? How does glowing in the dark help deep sea creatures?

A Bioluminescence is an amazing phenomenon to see in nature. Most of what we know about "living light" comes from studies of lightning bugs (or fireflies). The process usually occurs inside cells of the animal's light-producing organ. A chemical called luciferin combines with oxygen and they are converted to water and oxyluciferin. Energy is produced by the process and released in the form of light. The chemical reaction needs a third chemical (an enzyme called luciferase) present to stimulate the process, but the enzyme itself doesn't change in the reaction. It's a reversible reaction so the oxyluciferin can combine with water and be converted back to the original chemical--luciferin--ready to produce light another time. There are probably several different reasons why ocean animals have evolved the ability to produce their own light or bioluminescence in the dark deep sea. Animals use light as a way to communicate to other creatures OR as a form of camouflage that helps disguise the outline of their bodies in the darkness. Some animals (like the anglerfish and dragonfish) may use bioluminescent organs near their mouths to lure prey closer in for the kill. Other creatures may use light to advertise for mates of their own species--like the lanternfishes that have species-specific patterns of photophores on the underside of their bodies.
Judith L. Connor
Creatures of the Deep, February 1996



q Since the wood frog can freeze and thaw, does it have an internal "clock" to tells it the season?

A Yes, freeze tolerance is a seasonal phenomenon, not just for wood frogs but for almost all freeze tolerant animals. The exceptions to this are high Arctic and Antarctic insects that really could experience freezing temperatures in any month of the year. All animals, even ourselves, respond to internal clocks that are cued to the progression of the seasons and that prepare the animal for the activities or the environmental stresses that are specific to each season. Summer wood frogs are just as susceptible to freezing damage or death as are frogs like the leopard frog that spend the winter unfrozen at the bottom of ponds. In fact, wood frogs lose their tolerance of freezing quite rapidly over just a few weeks after they emerge from hibernation in the spring. One of the reasons for this is that they can no longer make the huge amounts of glucose cryoprotectant that they need to protect their cells during freezing.
Kenneth Storey
Going to Extremes, February 1997



q How do bees communicate?

A There are several mechanisms by which bees can communicate, ranging from simple to extremely complex. Some bees indicate by their sounds and behavior inside the hive that food is available somewhere outside the hive. They do not specify the location. Other bees follow each other to the food source. Others deposit a scent trail. After finding a good food source, a forager will fly back to the hive, but along the way she will periodically land and rub her mandibles against a piece of grass or a leaf. By landing every few yards, she deposits a trail of droplets on the ground. However, we do not understand exactly how other flying bees may follow this trail. Another scent mechanism is to deposit pheromones (special scent chemicals produced by the body) at the food source. Other bees can then home in on this scent (but only when they are near the food source). The most complex is the honey bee dance language. Honey bee foragers measure the distance from the hive to the food and also the angle of the food relative to the angle of the sun. Because the honey comb is oriented vertically, they perform a special waggle dance that indicates the sun-food angle on the vertical hive surface. This communication mechanism uses sounds, vibrations, and motions inside the hive. Incredibly, the bees also have an internal clock that guides them in using a their sun compass to calculate angles. When they cannot see the sun on a cloudy day, they can use small patches of blue sky to tell where the sun is, because their eyes are sensitive to ultraviolet light, something that we cannot see. The sun produces special patterns of ultraviolet light in the sky that the bees can detect. When the sky is completely overcast and they cannot see any blue sky, they rely upon landmarks. The himalayan honey bee, Apis dorsata, often collects food at night, and uses landmarks and the light from the moon and stars to help orient itself. However, it still measures the angle from the sun to the food source! How can it do this? Because it has a clock and a sun compass, it knows where the sun is on the other side of the world! If you observe the dances, you will see that it dances as if the sun were on the other side of the world.
James Neih
Expedition Panama, October 1997



q Why do bats sleep upside down?

A Why bats hang upside down is a really interesting question. Let me try to answer it. I think that it is largely to the construction of a bat's body, particularly the way how the wings are formed and attached to a bat's body. The thin membrane of a bat's wing stretches from its elongated fingers to the legs and attaches to the sides of its body. Further, in most bats, a large membrane connects both legs and is used by the bats to capture insects in the air like a pouch. Thus, the legs of a bat are not free but are "engulfed" by wing and tail membrane. Consequently, bats did not have the "freedom" like birds to develop many different kinds of legs like the long legs in storks or short legs in ducks. It appears that for a bat the easiest way to stow away the membrane is to hang upside down. Whether this is the main reason for it or not, I do not know. But looking at bats hanging from branches and ceilings it seems to be a rather logical explanation to me.
Elisabeth Kalko
Expedition Panama, October 1997



q I found it very interesting to see how smart a spider really is and to see the different prey-hunting techniques that Portia used. I wondered if there are any other spiders that use Portia's techniques?

A There are a number of other spider species which use Portia's techniques. Almost all the techniques Portia uses are used by at least one other species of spider. These include other jumping spiders besides Portia, as well as spiders in groups that are quite unrelated to Portia. The thing about Portia is that it does all the techniques any of the other species do, and it's fair to say it does the techniques as well as or better than the others.In the United States, the common long-legged spiders found in most people's basements, Pholcus phalangiodes, is an aggressive mimic like Portia. It will leave its web and go hunting other spiders in their webs, and lure them closely with web-borne signals like Portia does. Also in our country there are other jumping spiders that will use the detour behavior Portia does - see a prey spider, then take a roundabout route to get to it. This takes planning ahead. I suspect most jumping spider species will do this.
Stim Wilcox
Spiders!, April 1999



q Can other invertebrates learn a task by watching, like the octopus learned to open the jar?

A As far as I know, no other reports have been published on the same process. However, it should be noticed that among arthropods several species are reported to be able to benefit of the "others'" experience. As an example, foraging bees receive information about the food location by other animals using a well known communication dance: this is a different process - theoretically speaking - but in a very simplistic way could be considered similar.
Graziano Fiorito
Creatures of the Deep, February 1996



q What's the most remarkable thing you've ever seen a raven do?

A The most remarkable thing I've ever seen a raven do is rather than pecking little chips out of a big hunk of suet, as most birds do, this bird "sliced" off a big hunk that he could fly off with; he carved out a groove with dozens of pecks all aligned till he got the big chunk. That's planning, and postponing immediate gratification to achieve greater gratification later.
Bernd Heinrich
Animal Einsteins, January 1999



q Does Alex the parrot use language to express preferences, make choices or comment on the world around him?

A Yes, Alex is quite insistent about using his speech to get what he wants. If, for example, he requests a grape and I give him something else, most of the time he says "Nuh (his word for 'no') and requests the grape again. We can't really document if he is commenting on the world around him....if he says "yellow" when a student is wearing a yellow shirt, he might simply be practicing the term.
Irene Pepperberg
Animal Einsteins, January 1999



q Do you believe that cooperation and peacemaking may be instinctive behaviors among non-human primates and among humans, too?

A We don't use the term "instinct" anymore because everything people and animals do is determined by both biology and the environment. But if you mean that the tendency and capacity to restore relationships after fights is part of primate nature, I'd say yes. It is part of it, and the environment (for example, the culture in which you live, or the educational system) can either strengthen or weaken this tendency. This is also true for nonhuman primates. We once did a study in which we let young rhesus monkeys live together with stumptail monkeys. The first species is rather intolerant and aggressive, the second much more peace-loving. By the end of the experiment, the rhesus monkeys had changed their behavior, and had become as conciliatory as the stumptails. This shows that peacemaking is something that can be learned (in the same way that aggressiveness can be learned). The study was published by: de Waal, F. B. M. and D. L. Johanowicz (1993). Modification of reconciliation behavior through social experience: An experiment with two macaque species. Child Development 64: 897-908.
Frans de Waal
Prime Time Primates, February 1995



q How did you like working with chimps? Are they usually cooperative with the experiments, as we see on the show, or are they sometimes bored or uncooperative?

A Can't you tell that I LOVE working with chimps? I HAVE to be around them; it is a bit of a disease, I am afraid. The chimps have the full range of behaviors just as you see in your children or perhaps yourself! Some days they are absolutely wonderful, cooperative and so much fun; others days, they are spoiled brats (some of them, like Digger, who is an adolescent male about 9-1/2 years old, who loves to spit at the female chimps through the cage bars, and really make them mad! They scream and scream when he does this, and the more they scream, the worse he acts! Who does that sound like, eh? Any of you have any little sisters or little brothers who do those kinds of things?? No? Gee, I guess I was wrong; I thought that you would all really understand what kind of teasing and "sibling rivalry" I was talking about... The chimps often try to test the limits of our patience, for sure. But, everyone, chimps and humans alike, forgive and forget on a regular basis, and we continue to try to make our experiments more like fun games for both the chimps and their teachers. All in all, it is a wonderful, wonderful experience to share their lives, and none of us would give it up for anything!
Sally Boysen
Animal Einsteins, January 1999





 

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