Arizona's plants and animals are on the move. They have been for quite some time.
Not so long ago, spruce trees dotted the higher elevations of the Sonoran Desert and the Phoenix scene resembled the pinyon plains around Prescott, Ariz. Someday it may resemble the desolate dunes and barren environment of Yuma. Or it may be unlike anything in Arizona today.
The Sonoran Desert seems timeless, as if the saguaros have been standing here since the beginning of time with the same creatures roaming the desert. But saguaros and palo verdes are newcomers, arriving thousands of years after mankind. And some animals, such as the javelina, have only been around for a couple hundred years. Coatimundi didn't live in Arizona until recently and other species may be on their way here, either recolonizing the north or invading it for the first time. Some could be leaving or disappearing due to climate changes or problems associated with mankind.
The familiar desert scene is transforming in our lifetime, but its evolution is nothing new. Most plant and animal species are in close sync with their environment and the climate. If those change, so must the flora and fauna if they are to survive. Adjustments in distribution seem to have been the primary way that species have responded to past climate change," says a Pima County report for the Sonoran Desert Conservation Plan. Individual species respond by shrinking or enlarging their ranges in search of more comfortable microclimates.
Several border-crossing species have recently aroused the interest of biologists who want to know why they are heading north.
Although the remnants of many other vertebrates were found in the trash middens of prehistoric Indian ruins, no javelina, coatimundi or opossum bones were found, said Randy Babb of the Arizona Game and Fish Department. Nor do early American explorers and settlers write of encountering them. Surely, they would have noticed a skinny, bristly pig and a noisy critter with a raccoon tail. Nobody seems to have seen them, yet now coatimundi are a common sight in Southern Arizona and herds of javelina roam desert washes.
Javelina originated in the Western Hemisphere 35 million years ago. Since then, many forms have appeared and disappeared. Remains have been found as far north as the Yukon Territory of Canada. Only in the last few decades have they appeared in Arizona.
"Javelina are now in areas where they didn't exist 20 years ago," said Ron Day, a ranger with the Arizona Fish and Game. "They are found all the way up to the rim of the Grand Canyon. We don't know if they can cross that. And on the other side they would find a more severe environment with Utah's cold winters," he added.
The slender javelina are poorly insulated. They are a subtropical animal, one of four collared peccary species found in Central and South America. Their bodies can maintain full hydration under moderately hot and dry conditions, reducing the need to stay near a water supply. If they can eat juicy succulents, such as prickly pear cactus, so much the better.
They are adaptable, living in habitats that range from humid rainforests to scrub oak to deserts. Their diet is mainly vegetarian, but they will eat about anything they can find on the ground - eggs, grubs, worms, lizards, snakes. In the last few decades they have added table scraps, dog food, bread and birdseed to their diet.
Day said javelina are taking advantage of riparian corridors such as Clear Creek and Leonard Canyon to expand their territory. In these northbound canyons, javelina have water and an ample food mass of manzanita and juniper berries, turbinella acorns and green vegetation. The skitterish creatures will scatter like leaves when startled, but they don't seem to have an aversion to human occupied sites, which may be helping them in their travels northwards.
Another species on the move is the Mexican opossum (Didelphis Californica), a relative of the Virginia opossum of North America. It is found in Central America, Mexico and now in Southeastern Arizona. Yet there is no archeological evidence of them in our state before 1700, when their bones start appearing in Indian trash middens, Babb said.
The lively, ring-tailed coatimundis are also new Arizona residents. The males are solitary, except at mating time, but females live in gregarious social groups of four to 30 animals. With their striped tail held aloft, and noisy behavior, they are hard to miss. Equally comfortable on the ground or climbing trees, the coati spend their days searching for insects, fruit, small mammals and eggs to satisfy their insatiable appetites.
They frequent some campgrounds and picnic sites in Southern Arizona and have even been spotted in the McDowell Mountains northeast of Phoenix. The coatimundi (Nasua nasua) is one of four species of coati native to the forests of Mexico and Central America.
"They were unknown in Arizona despite several large expeditions that collected many species and identified a number of new species in the mid to late1800s," said John Koprowski, associate professor in the Wildlife and Fisheries Science School of Natural Resources at the University of Arizona in Tucson.
"The published folklore of the native Pima peoples of the region does not include mention of coatis. They were first reported in the Huachuca Mountains about the turn of the last century and have since been reported for most of the sky islands of Southeastern Arizona with some reports of them north of Phoenix. Some of these may be due to releases from the pet trade," he added.
Jaguars and their small, mysterious cousins, the jaguarundi, may be undergoing a similar northward migration pattern, perhaps due in part to increased protection and relief from hunting pressures, Koprowski said. They and the ocelot are listed as endangered species.
Jaguarundis (Felis jaguarondi) are the Sonoran Desert's mystery cats, according to the Arizona Sonora Desert Museum. Each year, there are a number of sightings but a hide and skull have never been recovered, or a photo taken of one in the wild. Still, since these small cats can't travel long distances, they are believed to be residents of our state.
Some experts say the jaguars are just moving back into their former territory. Small populations were known to exist in Arizona as far north as the Grand Canyon. There are occasional sightings and photos of North America's largest cat in Southern Arizona, and one was taken from the Doz Cabezas Mountains in 1986. According to Babb, a jaguar was killed in the White Mountains of Northeastern Arizona in 1963.
"It's quite possible that they have been here for a while, but went unnoted because their territory is widespread and their population is low-density," Babb said.
The ocelot (Leopardus pardalis), also known as tigrillo and painted leopard, is more adaptable than the jaguar and thus may be better able to survive in dense cover, even near large towns. It is about the size of a bobcat but has a long tail. Each animal's coat pattern of spots, lines and rings is unique and does not match even from one side to the other, camouflaging them well in subtropical thorn forests such as mesquite.
Ocelots are nocturnal and sometimes travel and hunt in pairs. An Arizona Game and Fish report says they are mild mannered, and thus easily trapped and shot. Although many countries, including the United States, prohibit the hunting of ocelot, they are the most frequently hunted cat in Latin America.
According to Arizona Game and Fish Department, "The ocelot may be repeating the northward expansion of the javelina, coati-mundi, and other neo-tropical invaders into the San Pedro River Valley, Ariz."
Why are these animals heading for the border? There are several hypotheses, according to Koprowski. In addition to changes in hunting regulation, vegetation changes due to differing fire patterns may be a factor, said Koprowski. He said some scientists also believe it is due to climate change and the associated vegetation change.
The animals may be looking for cooler climes. According to a study of tree rings by Julio Betancourt of The University of Arizona Desert Laboratory, temperatures in the 20th century are the highest in over 1400 years
Temperature is not the only environmental factor to affect flora and fauna populations. They are also impacted by changes in seasons, stream flow or the amount of rainfall. Many species are affected by fire, drought, erosion and man-made changes. The masked bobwhite quail population, for example, declined due to overgrazing of its grassland habitat during a drought period.
Diana Stuart, a conservation biologist and research technician, said, "If a species doesn't like what's happening to their habitat, they may try to shift to a more comfortable spot - if it is available. Urbanization or natural barriers may block the way."
Stuart one of several ASU professors participating in the Central Arizona-Phoenix Long-Term Ecological Research (CAP LTR) program, a project funded by the National Science Foundation and focused on man's impact on the arid arid-land ecosystem.
"A species can be wiped out if it tries to shift its territory when the old environment becomes inhospitable and it can't because of a human delineated border," Stuart said.
For some species that could be the end of the road.
"There could be habitat pressures in Mexico, and the animals are trying to move north into Arizona. If we think there are plenty more down there and kill off any that come across the border, that could be the last of them," she said.
To understand what is happening with global warming and how it affects life, scientists are looking at climate patterns of the past. It's a complex story of cycles within cycles bringing about wide variations in temperature and rainfall. The Earth's climate has been in constant flux since the beginning of time.
"Some cycles are very long-term, such as the 100,000 year glacial periods, others such as El Nino come every few years," said Anthony Brazel, Ph.D., a climatologist who is also part of the CAP LTR project.
Milankovich Cycles are 23,000 years long and are determined by variations in the Earth's orbit, the wobble of the Earth on its axis and its inclination to the sun; all affect the amount of solar radiation and which part of the earth receives it. With new technologies such as satellites and computers that can compile mounds of data into working models, they look for patterns of climate change. Some are predictable, some are not.
Researchers at the University of Washington have recently discovered a decades long climate shift, known as the Pacific decadal oscillation. Water and air temperatures change gradually throughout the entire Pacific Basin, fluctuating over 10-30 year periods and affecting weather patterns throughout the West. The better known El Nino, a weather phenomenon of the tropical Pacific Ocean that affects climate in the Southwest, is only one phase of the cycle.
"How El Nino is in sync with the Pacific decadal oscillation determines whether a year will be really wet or really dry in Arizona," Brazel said.
He said climatologists are also looking at rapid climate shifts, such as dramatized in the recent movie, "The Day After Tomorrow."
"The change can be a lot more abrupt than previously thought, due to salinity changes in the oceans and other factors," Brazel said.
Extreme variations are the norm in the Southwest, according to Joe McAuliffe, Ph.D., director of research at the Desert Botanical Garden in Phoenix. "We go from boom to bust, and rarely have a rainfall that is 'average,'" he said.
Written records show a 15-year period of extreme drought beginning in 1890, followed by a very wet year and flooding in 1905. These extremes led to the decision to build Roosevelt Dam to conserve and control water in Arizona. The 1950s were another extended drought period which had a profound effect on plant life.
"We had a 20-year period of unusually wet weather, but now we are about six years into a Pacific decadal oscillation, a period like the 1950s drought," said McAuliffe.
"Big changes are not unique, but this drought could be a very important phenomenon determining what happens in the future. It is like resetting the clock," he said.
"This one is producing changes in the plant community," McAuliffe said.
"Most plant species will come back but there will be changes in the mix -the percentages of plants. Potentially, it has the same effect as a fire. The bursage and the creosote may be knocked out, allowing the brittlebush and exotic grass species to take hold," he said.
Despite repeating cycles and wide variations, records indicate an overall warming trend since North America experienced its most recent "Glacial Maximum," 18,000 years ago, said Brazel.
By looking at tree rings, pollen deposits in ancient lake beds, glacier deposits, packrat middens and other records of the earth, scientists can see that the American Southwest was much wetter and cooler in the last ice age. Deep lakes filled many now arid valleys and the desert supported plants and animals that can only live farther north or at higher elevations today.
Sometimes plants and animals fight the tide of climate change by moving up, a situation most evident in Arizona's unique "sky islands" As temperatures warmed up in the Sonoran Desert, many plants and animals found their comfort zone by shifting to a another elevation within the same general area. This appears to be what happened on the top of some mountain peaks in Southern Arizona. These sky islands are remnants of the Pleistocene environment when the entire region was a cooler, wetter place. As the climate became hotter and more arid, the desert expanded and plants and animals retreated upwards, Stuart said.
It is the only mountain complex in the world that spans the temperate and subtropical latitudes. Rocky Mountain flora and fauna mix with those of Mexico's Sierra Madre resulting in an extremely rich and diverse biological community of nearly 100 species. Still, the peaks can become death traps for a species if something happens to their environment since they can't change their location. Most species are unable to cross the vast expanses of desert between this archipelago of peaks to get to a new mountain habitat.
While botanists once thought of plant communities as complete packages that moved together, it has become apparent that the composition evolves with some species dropping out and others filling in over time.
Some species may need to follow another to survive. For instance, most yucca species have a symbiotic relationship with particular moth species. The lifecycles of both plant and animal have become intertwined and synchronized for mutual benefit. The moth lays its eggs on the yucca's ovary and the larvae eat some of the pollinated seeds at they hatch. The moth then emerges just in time to pollinate the yucca's bloom.
"An 'obligate species' is one that depends upon a certain other species for his livelihood. If that other species disappears, he's out of luck. The ferruginous pygmy owl, for example, needs saguaro cactus. His range has been severely cut back and he is at the northern end of it, so if something happens to his environment, he could become extinct," Stuart said.
Birds are more mobile than plants and quadrupeds and so should be able to adjust their habitat more easily. Migrating species may extend their stay in the summering grounds or go further south in the winter. Stuart cautions that sighting new birds doesn't mean they have permanently changed their habitat.
"From one year to the next, you can see an invasion of a new species, but the birds may not return the next year. What we are looking for is a permanent occurrence of a new species. That usually means a period of decades and it only happens occasionally," Stuart said. Real changes usually take a long time to occur.
Because of their mobility and sensitivity to small changes in their environment, birds can be an excellent indicator of climate change.
"There's a reason the miners used a canary to warn them of danger." Stuart said, with a smile.
Whether the northward migration of Arizona's plants and subtropical species is an indication of global warming has yet to be determined. But like the miner's canary, the javelina, coatimundi and opossum may be harbingers of change.
Sources
Birds, General Animal Info
Randy Babb, Arizona Game and Fish Department, Mesa Office
Diana Stuart, Conservation Biologist, Research Technician, CAP LTR project 480-965-4642, DianaStuart.@asu.edu In-person interview, e-mails
John L. Koprowski, Associate Professor, Wildlife and Fisheries Science, School of Natural Resources, University of Arizona, Tucson, AZ 85721 USA, - e-mails
Javelina
Randy Babb, Arizona Game and Fish Department, Mesa Office, phone interview
Coatis
John L. Koprowski, Wildlife and Fisheries Science, UofA, e-mails
Jaguarundis, Jaguars, and Ocelots
Ron Day, Arizona Game and Fish Department, phone interview
2004-01-24 (AMS) Leopardus pardalis - Unpublished abstract compiled and edited by the Heritage Data Management System, Arizona Game and Fish Department, Phoenix, AZ
Final rule, U.S. population of jaguar, WAIS Document Retrieval, U.S. Fish & Wildlife Service
Plants
Dr. Joe McAuliffe, Director of Research at the Desert Botanical Gardens in Phoenix, AZ 480-941-1225 In-person interview
Climate/Landscape
Dr. Anthony Brazel, ASU Climatologist, 480-965-6436 - In-person interview
Climate: Julio Betancourt, The University of Arizona Desert Laboratory, 520-629-9455 phone, e-mail interview
USGS - Landscape Changes in the Southwestern United States
Past Climate and Vegetation Changes in the Southwestern United States, Robert S. Thompson, U.S. Geological Survey and Katherine H. Anderson INSTAAR, University of Colorado
An Overview of the Implications of Global Change for Natural and Managed Terrestrial Ecosystems
