Click here for the latest Arizona mammal update.

Arizona’s premier mammal species, and one of the very youngest, the humans (Homo sapiens), congregates in urban habitats that most other mammals avoid.  Residents of the scattered human homes of the Agua Fria River Basin often see the 15 to 20 common species that are active during the day and early evening.  Residents of large urban areas such as Phoenix and Tucson rarely see more than three or four species.

Developers are eager to fill the Agua Fria River Basin with homes and businesses.  As the human population of the Basin grows, the number of familiar mammals will decline.

Of course, almost all species decline as the human population grows.  When I began high school in 1960, the human population of earth totaled three billion.  Forty years later in 2000, it had doubled.  From 1960 to 2000 the U. S. population grew from 180 million to 280 million, and will add more than 100 million during the next 25 years.

In Arizona the extinction of other species by humans is occurring most rapidly for species that spend much of their lives in or near water (look at the blog posts on fish and amphibians).  This is because toxic wastes flow down slope to the streams and lakes, and because the streams and lakes are being modified.  Over the next 100 years many species will disappear.  Mass extinctions have occurred before in Earth’s history, but it is likely that none were as large or sudden as the one that is being caused now by humans.  Certainly no other single species has ever achieved such a great destruction of life on earth.

Mammals are described in numerous field guides and websites (e.g., Kays and Wilson, 2002, National Wildlife Federation, AZGDF).  Field guides often illustrate animal tracks, and some (e.g., Halfpenny 2000) are devoted to this essential subject.  A complete field guide to Arizona’s 144 mammal species can be assembled and downloaded from the North American Mammals page of the Smithsonian Institution’s National Museum of Natural History web site.  The downloaded field guide will have a page for each species with a picture, distribution map, and description.

The photograph shows a Rock Squirrel sitting on a fence post. 

More than half the 144 Arizona mammal species are present in the Agua Fria River Basin, but only 15 to 20 are seen very often.  Most common are Cottontail Rabbits, Jackrabbits, Mule Deer, Pronghorn (Antelope), Collard Peccary (Javelina), Coyotes, Raccoons, Skunks, Bobcats, Foxes, Rock Squirrels, and Valley Gophers.   Smaller species, the chipmunks, rats, bats, mice and voles are often seen, but may not be close enough for identification.

Names Primer:  The Lagomorpha

This and other checklists on the blog include scientific names consisting of two or three italicized words:  the genus, species, and subspecies.  Most are derived from Latin.  Scientific names may be unfamiliar, but they are useful because, unlike common names, they are the same everywhere.  Common names for a species are often different across regions.

Animal species are grouped according to their similarity.  Similar species are assigned to the same genus.  Similar genera are assigned to the same family.  Similar families are assigned to the same order.  For example, the order Lagomorpha includes two families:  Leporidae (Rabbit family) and Castoridae (Beaver family).  The Leporidae family includes two genera:  Lepus (jackrabbits) and Sylvilagus (cottontails).  The genus name, Sylvilagus, was formed by combining the Latin word sylva (wood) with the Greek word lagos (hare).  Sylvilagus includes thirteen species.  One of them, the Desert Cottontail, was named Sylvilagus audubonii.  The species name is the ‘Latinized’ version of Audubon’s name.  It was probably assigned because Audubon was the first to determine that Desert Cottontails were a separate species.

Species diverge when their population becomes separated.  Slight divergences are recognized by adding subspecies names.  If the divergence becomes so great that the subspecies are no longer able or willing to interbreed, a new species is designated.  This can be confusing.  For example, the Arizona Game and Fish Department (AZGFD) lists 13 rattlesnake species for the state.  Counting the currently accepted subspecies produces a total of 20 different rattlesnakes living in the state.  Humans are affecting all Arizona’s rattlesnake species and subspecies.  It is in this regard that subspecies are particularly important.  The habitat of one subspecies may be more heavily impacted than the habitat of the other subspecies.  Thus, it is not helpful to list an entire species as needing protection when it is only one of its subspecies.

Mammal References and Notes

American Society of Mammalogists:  http://www.mammalsociety.org,

AZGFD, Arizona Game and Fish Department:  http://www.azgfd.gov .

Defenders of Wildlife:  http://www.defenders.org.  News:  www.defendersblog.org.

Halfpenny, J.C., and T. Telander.  2000.  Scats and tracks of the desert southwest:  A field guide to the signs of 70 wildlife species.  The Globe Pequot Press, Guilford, CN.  144 p.

Hoffa, R.L., and W. Anderson.  1996.  Coexisting with urban wildlife:  A guide to the central Arizona uplands.  Sharlot Hall Museum Press, Prescott, AZ.  123 p.

Kays, R.W., and D.E. Wilson.  2009.  Mammals of North America (second edition).  Princeton University Press, Princeton, NJ.  248 p.

National Wildlife Federation:  www.nwf.org.

Organization for Bat Conservation: http://www.batconservation.org/

Smithsonian National Museum of Natural History:  www.mnh.si.edu  and for conservation status:   http://www.mnh.si.edu/mna/search_status.cfm

U. S. Endangered Species Act.  1973. The act and related laws are discussed at:  http://www.fws.gov/laws/lawsdigest/ESACT.html.

U. S. Fish and Wildlife Service:  http://www.fws.gov.

U. S. Forest Service.  2007.  Regional Forester’s list of sensitive animals:  http://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fsbdev3_021328.pdf.

World Conservation Union:  www.iucn.org .

Symbols Used in the Checklist

            An asterisk (*) in the left check box indicates Tier 1A “Species of Greatest Conservation Need” (Arizona State Game and Fish Department).  The letter S (S) in the check box indicates sensitive species (U. S. Forest Service).  The letter T indicates species that are candidates for federal protection and species that are threatened as defined by the U. S. Endangered Species Act.  The letter E indicates species that are endangered (E) as defined by the Act.

The scientific names in the checklist are linked to the Smithsonian Museum of Natural History website