Panthers in Peril: with help from their cat relatives, the endangered Florida panthers are back from the brink.

DID YOU KNOW?

* The chemical symbol for mercury, Hg, comes from the Latin word "hydrargyrum" meaning "liquid silver."

* In the 1950s, industrial dumping of mercury into Japan's Minimata Bay resulted in one of the first cases of widespread mercury poisoning. Hundreds of people from this fishing region died because they regularly are mercury-contaminated fish. Today, mercury poisoning is often called Minimata Disease.

CRITICAL THINKING:

* Suppose you could transport a container of mercury safely to the planet Mercury. The planet has surface temperatures of 467[degrees]C (872[degrees]F) during the day and -183[degrees]C (-300[degrees]F) at night. Would the mercury metal remain a liquid? (Answer: No. Mercury freezes at -38.9[degrees]C [-38[degrees]F]).

CRDSS-CURPJCULAR CDNNECTIDNS:

Literature/Art Mercury was the Roman god of speed and commerce. In ancient Rome, coins typically featured a picture of a Roman god or goddess on one side. Research these deities. Then, select one to illustrate your own "Roman coin."

RESOURCES

* Grolier search term: Mercury and element

* Find games, quizzes, and printable periodic tables here: http://education.jlab.org/itselemental/index.html

Three times a week, Mark Lotz, a biologist with the Florida Fish and Wildlife Conservation Commission (FFWCC), hops aboard a small airplane and takes to the skies above Florida's forests. This isn't a leisurely flight. Rather, Lotz is monitoring the population of one of the most endangered species (group of organisms in danger of dying out) in the United States--the Florida panther, or Puma concolor coryi (POO-muh kuhn-KUH-lur COR-ee-eye).

In the early 1900s, hundreds of Florida panthers roamed the Southeastern U.S. (see map, below). But habitat loss and hunting nearly wiped them out. By 1990, the cats had vanished from every place except Florida, says Larry Richardson, a biologist at the Florida Panther National Wildlife Refuge. "We were basically watching this subspecies [subdivision of a species usually based on geographic range] of the mountain lion go extinct [no members of the species remain]," says Richardson.

Time for action: A decade ago, biologists took an unusual step to help the vanishing panthers. They released a group of Texas cougars--the panthers' nearest relatives--into South Florida. They hoped the panthers and cougars would mate, boosting the panther population. Read on to discover how their plan is faring.

TOP PROWLER 

Catching a glimpse of a panther in the wild is a challenge. The cat's earthy coloring acts as camouflage, helping it blend in with palm trees and leafy areas. Also, this top predator (animal that hunts and kills other animals for food) is nocturnal. That means it waits until dusk to hunt for a tasty meal.

What's on the menu? Using powerful jaws and teeth, this carnivore (meat-eater) can chow down on 50 deer-size animals in a year.

It takes a lot of land to feed the cat's favorite prey--veggie-loving white-tailed deer, and wild hogs. And since panthers aren't big on sharing their meals--or their homes--with one another, each cat needs its own supersize territory. The home range of a single male boasts an area of about 640 square kilometers (250 square miles). Now that's a roomy pad.

CROWDED CATS

Unfortunately, Florida doesn't have many vacancy signs for panthers. From 1935 to 1990, nearly 5 million people settled in the Sunshine State. With so many newcomers clearing land to build homes and roads, panthers' habitat diminished. "Habitat loss is one of the main threats to the Florida panther," says Lotz.

To make matters worse, the Florida panther didn't become protected as an endangered species until 1967. Before then, the cats were fair game. Hunters killed the panther for its tough skin and tawny-colored coat. And farmers, fearing the predator would harm their livestock, also hunted these cats.

GENE SCENE

By 1990, fewer than 50 panthers existed in the wild. That spelled trouble for the cats. "What started developing was an inbred [too closely related] population, with very little genetic diversity," says Richardson. That means as the number of panthers dwindled, so did their gene pool (total collection of genes, or units of hereditary material, in a species).

Like you, panthers inherit traits, or characteristics, from their parents in the form of genes. Some genes, called recessive genes, are weak and show up only if the offspring gets two copies of that gene--one from each of its parents.

In the past, when the cats' population was strong, there were lots of panther parents. That meant the kittens ended up with an assortment of genes. But as the number of Florida panthers shrank--and the grab bag of genes got smaller--the chances of offspring inheriting two of the same recessive genes increased. Some of these weak genes can be deadly.

The panthers' vanishing gene pool led to heart defects and infertility--both a result of recessive genes. "We were watching the prevalence of genetic inbreeding begin to wipe out this cat," says Richardson.

PURRFECT MATCH

To strengthen the cats' gene pool, biologists turned to the Texas cougar. "In 1995, [the FFWCC] brought in eight female Texas cougars, and released them in different places throughout South Florida," says Richardson. That way the cougars would mate with Florida panthers, and produce offspring with both cougar and panther genes.

The plan worked. By 2002, five cougars were proud mothers of at least one litter of kittens. The kittens' health: "Immediately, all of the inbreeding problems disappeared," says Lotz.

Following that success, biologists removed the cougars from the panthers' habitat in 2002. "We didn't want them to produce more than [two litters], because it would [overwhelm] the original Florida cats' gene pool," says Lotz. As it is, the panther population has 20 percent of the cougars' genes. That's enough diversity to keep the panthers safe for a while, but not a big enough change that biologists would call the cats Texas cougars.

PANTHER PATH

Today, nearly 100 panthers are on the prowl in South Florida. But they aren't completely out of harm's way. Since the cats are secluded in a small area in Florida, they could face inbreeding problems again in the future. "Even with Texas [cougar] genes, it's still a geographically isolated population," says Richardson.

For now, biologists will continue to protect and monitor the imperiled cat. And they're not just protecting panthers. "If you save the Florida panther, you're also saving what is really essential: habitat," says Richardson. "That's incredibly important to us."

Nuts & Bolts

A population is a group of organisms of the same species that live in the same area. Its size can vary over time depending on the number of births and deaths. When there are more births than deaths, the population grows. But it won't balloon forever. Environmental factors, such as food supply and suitable habitat, keep a population in check.

DIRECTIONS: On a separate piece of paper, answer the following questions in complete sentences.

1. By 1990, the Florida panther population had been reduced to fewer than 50 animals. Identify two factors responsible for this decline.

2. How did the introduction of Texas cougars helped revive the Florida panther population?

3. Why do male panthers travel over such large areas of land to hunt for prey?

4. Summarize the actions taken by humans to prevent the extinction of Florida panthers.

Panthers In Peril

1. Hunting and loss of habitat are the two factors primarily responsible for the population decline.

2. Introduction of the Texas cougars helped revive the panther population by increasing the size of the gene pool, decreasing the amount of inbreeding, and decreasing the number of harmful recessive genes found within the population.

3. Male panthers must travel over such large areas of land because their prey, mostly deer and wild hog, require vast areas of wilderness to find enough vegetation to survive.

4. Actions taken by humans to prevent the extinction of

Florida panthers include the following: population monitoring, introduction of Texas cougars into the population, and protection of the panther as an endangered species.

HANDS-ON SCIENCE NO AB REQUIRED

Read "Panthers in Peril" (p. 14). Then try this hands-on experiment to get a cat's-eye view of survival in the swampy forest.

PREDICT

List three resources that Florida panthers need to survive. What will happen to their population if these resources are unavailable?

YOU NEED

labeled, colored index cards (four colors: yellow = panther, green = habitat, blue = water, and white = prey) * marker * chalk * chalkboard * graph paper * pencil

PROCEDURE

1. Give each student four index cards, one of each color.

2. Have your teacher count off students in groups of four. The is ("panthers") stand across the room from the 2s, 3s, and 4s ("resources").

3. Have your teacher record on the chalkboard the number of panthers and the total number of resources.

4. Each "resource" student then holds up one resource card of their choice (habitat, water, or prey). Panthers choose a resource they'd like to find, and hold up that card, plus their panther card.

5. When your teacher starts the round (a "season"), the resources and panthers will hold up their chosen cards so other students can read them. Panthers walk around to try to find their resource. (Only one panther per resource!)

6. If the panther finds its resource, that resource becomes a panther in the next round. This signals that the panther has met its needs and produced offspring. If the panther doesn't find its resource, it "dies," and becomes a resource in the next round. That's because with fewer panthers, there are more resources to go around.

7. Your teacher ends round 1 after the panthers have found--or failed to find--their chosen resource.

8. Your teacher then records on the board the number of panthers and the total number of resources.

9. Repeat Steps 4 to 8 for three additional rounds. (Note: If you'd like, you may use the same resource card that you used in prior rounds.)

10. Have your teacher collect all of the resource cards and mark the back of three of each resource type using a marker. The mark represents a "human pressure" such as the use of natural resources.

11. Have your teacher pass out the resource cards. Then, repeat Steps 4 to 9. If a panther finds a marked resource, it dies and leaves the game. That's because human pressures both cause populations to decrease and leave resources scarce.

12. Using your data, make two double-line graphs showing the panther and resource numbers over time, with and without human pressures.

CONCLUSIONS

1. Using your graphs, explain what happened to the panther population over time, without human pressures.

2. How did results change when human pressures were added? List possible pressures.

3. Why would you use a line graph rather than a bar graph?

HANDS-ON, p. 17

1. The graphs should show increasing resources followed by increasing panther population. When panther numbers increase, the cats start to use up their resources, leading to a decrease in resources. But if resources become too scarce, the panthers could go extinct. That's because the Florida panther needs habitat, water, and food to survive. These factors are called limiting factors, because as they decline, the panther population also declines.

2. Results will vary. As human pressures increase, wildlife resources generally decline. Compared with the rounds without human presence, the panthers exposed to human pressures will decline more rapidly. Some examples of pressures: residential buildings replacing natural habitat; less water for panthers as humans consume it.

3. In general, a line graph is best suited for showing changes over time. The dependent variable was the panther population, which changed in response to the resource numbers.