Rodents!
The most successful order of mammals on the planet.
According to your text, the order Rodentia includes roughly 2,277 species (more species are being discovered)
There are 33 families. We will not go through all 33 families!
Have radiated into numerous niches, sometimes surprisingly so:
Fulfill the role of other mammals in other parts of the world (e.g., rabbits or even hippos).
One of three orders of Eutherian mammals to have reached Australia on their own (the others are bats and Carnivores (not dingos - pinnipeds)).
Major characteristic is a pair of continuously growing upper incisors.
These are continuously worn down; outer surface is covered with enamel and is hard.
Inside surface is soft and wears away
Leads to typical chisel shape of rodent incisors.
Rodents are subdivided into different sub orders based mostly on the attachment site for jaw muscles (see fig. 13-3 in text if interested).
First fossils date back about 57 mya, to late Paleocene.
We will cover all U.S. families as well as a selection of others.
Family Aplodontidae:
Only one species - the mountain beaver - not related to beaver.
California and Pacific Northwest.
Totally vegetarian, lives in moist areas (in mountains).
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Family Sciuridae:
One of the largest and best known families.
Includes squirrels, prairie dogs, marmots, etc.
1/1 0/0 1-2/1 3/3 Mostly diurnal (some exceptions like the flying squirrel).
Locally we have gray squirrels, woodchucks, chipmunks, flying squirrels (southern) and a few odd fox squirrels and red squirrels.
Others are also well known: prairie dogs, marmots, large number of ground squirrels out west, etc.
Gray squirrel has been “exported” to Great Britain, Pacific Northwest, and South Africa. In all these places it has become a serious pest!
Black “gray squirrels” are due to an allele for black color.
Will build nests in trees.
Also bury nuts and then look for them later (important source of new seedlings).
Chipmunks hibernate to overwinter (probably will be disappearing fairly soon).
Note: fox squirrels and gray squirrels are not hard to tell apart - the fringe of the tail in fox squirrels is always yellow, and in gray squirrels is always white.
Family Castoridae:
Two species, American beaver and European beaver.
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Extensively modify the habitat they're in:
Cut down trees, build dams (and maintain them).
Create large amounts of wetlands (parts of Huntley Meadows are the responsibility of beavers).
Remain active over winter (eat bark (cambium) of branches they've stored.
Excellent swimmers; have adaptations to help them move around underwater (see text if interested).
Use flattened tail for propulsion, but also to “slap” water as a warning about predators.
Once seriously endangered:
Fashion for top hats made out of beaver fur.
Fortunately, have recovered well (and very few people wear top hats these days).
(In some areas are considered a major pest). Family Geomyidae
Pocket gophers.
Not that well known around here since they occur mostly out west.
Fossorial - usual adaptations to living underground (large forearms, small eyes, reduced ears, etc.)
Huge proliferation of species.
Possibly due to local populations becoming isolated.
Even your text calls this a taxonomic “mess”.
Fur color often matches soil color.
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Family Heteromyidae
Kangaroo rats.
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Mostly western, but also into South America.
Generally adapted for jumping (hopping) with large hind feet.
Many are adapted to desert life and never need to drink (get all their water from “dry” seeds).
Fairly common in many areas.
Have pouches that can store seeds (also in pocket gophers).
Family Dipodidae
Won't say much about them except that they seem to be the ecological equivalent of the Heteromydids in the Old World.
Have enlarged hind feet (different bones), live in deserts, etc.
Commonly called Jerboas.
(Note that one genus of Hetermydids is called “Dipodomys”) Family Cricetidae
One of the largest families of rodents (2nd largest).
Over 681 species.
Wide spread in both hemispheres.
Hamsters, lemmings, wood rats, deer mice, voles, muskrats, etc.
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Mostly vegetarian but some exceptions:
Grasshopper mice (Onychomys) are carnivorous, eating anything from insects to other mice, small snakes, scorpions.
Seem to be immune to the venom of scorpions and snakes
“Stalk” their prey.
Some other better known members:
Hamsters - obviously a well known pet.
Lemmings - notorious for huge population cycles (will cause mass emigrations (mass suicide is grossly exaggerated).
Deer mice - very widespread. Probably more scientific papers on “Peromyscus” than most other mammals. Several species around here.
(P. maniculatus and P. leucopus are not that difficult to tell apart when looking at their fur (look at the tail); skulls are essentially impossible to tell apart.)
Woodrats - will often collect “junk” and build nests. Sometimes called packrats. A local species (Neotoma magister) is endangered.
(Recently split off from Neotoma floridana (the Eastern wood rat)).
Voles - Around here, Microtus. Generally have short tails, prefer grassier areas (e.g., Meadow vole, Microtus pennsylvanicus)
Family Muridae
The largest family of rodents, with over 730 species.
1/1 0/0 0/0 3/3 Mostly Old World, but some important exceptions.
Contains rats, mice, gerbils, and a large number of other species.
Gerbils occupy desert regions and are (again) similar to the Heteromydids.
Can also survive without water (get water from seeds).
Rats and mice (Rattus rattus, R. norvegicus, and Mus musculus) have a long association with humans.
Humans have distributed these to all parts of the world.
In U.S. the brown or roof rat has been displaced in many areas by the Norway rat.
Are considered pest species;
Destroy huge amounts of food.
Have (in the past) spread disease including the plague.
(Killed 1/3 of the human population).
Rats are easy to see - just walk around downtown, particularly near subway entrances.
Are also used in research.
Are not the only ones with associations to humans.
Rat populations booms have been studied in southeast Asia where populations erupt as a result of bamboo die-offs.
Causes massive damage to human crops.
Some rats are worshiped in parts of India.
Recently a new species of spiny rat (Halmaheramys bokimekot) was discovered in Indonesia (made the news in the last few weeks).
Family Pedtidae
Springhares.
Only two species. Both can jump very well.
Vegetarian; dig burrows, but only in soil that's easy to dig through. Live in large colonies.
Nocturnal.
Family Diatomyidae
Thought to be extinct; then in 2004 a rodent (on a skewer) was discovered to represent this family.
(Don't worry about memorizing this family).
Family Bathyergidae
Mole rats, including the naked mole rat.
Sub-Saharan Africa.
Completely fossorial. Many depend on a single food plant.
Naked mole rat is esocial - lives in colonies with single breeding female.
Rest of colony is divided into castes (workes, nonworkers, etc.).
Family Hystricidae
Old World porcupines.
Africa, Asia, southern Europe.
Some speculation that ancient Romans introduced porcupines to Greece.
Terrestrial, dig burrows.
Can “warn” predators by rattling quills. Also prominently marked.
Family Erethizontidae
New World porcupines.
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Native porcupine is mostly northern and western in distribution.
(Start seeing them in Pennsylvania)
Eat variety of vegetation; in winter switch to bark. One source mentions antibiotic properties of their skin (due to sticking themselves when they fall out of trees). Are quite arboreal.
Are preyed on, but predators are often harmed as well.
Common roadkill further north.
Family Chincillidae
Chinchillas.
Wild populations are critically endangered due to the fur trade.
Fur is very soft.
Are now raised for fur, but this hasn't caused a drop in poaching.
Also popular as pets.
Western South America, Andes.
Herbivorous. Can run well for considerable distances.
Family Caviidae
Guinea pigs, maras, capybara.
Unusual group - includes some members that look more like small gazelles, and one that looks like a very small hippopotamus.
South American.
Maras are sometimes called Patagonian hares. Live in large groups and have excellent running ability.
The capybara is the largest rodent (Wikipedia now claims two species, text one). Text mentions weights up to 70 kg.
Semi-aquatic, can swim and dive.
Raised for food in parts of South America.
(Catholic church classifies these as “fish”, meaning you can eat them during Lent).
Extinct form thought to weigh about 200 kg (that's over 440 pounds!).
Guinea pigs are popular pets. Originally domesticated for food.
Family Dasyproctidae
Agoutis.
South American in distribution. Generally in forests.
Run well (will often wait until predator is close, then rapidly accelerate away).
Family Cuniculidae
Pacas.
Large south American rodents. Used to be classified with agoutis.
However, don't move very quickly and escape by moving into water.
Capable swimmers.
Construct burrows.
Many populations have declined drastically.
Are being hunted for meat, and have slow reproductive rate.
Family Myocastoridae
Nutria.
Introduced into many areas (North America, Europe).
Originally introduced to spur the fur trade.
Now a major pest species causing millions of dollars in damage.
Destroy waterways, native plants, etc.
Aquatic, herbivorous.
Lives in burrows next to water ways.
Common in areas close by (e.g., Blackwater NWR, where it is a major pest).
Family Capromyidae
Only mentioned because most are in serious trouble (text says 23 of 35 species are now extinct, with the rest seriously restricted). Cuban hutia is an exception - seems to be doing well (but is hunted).
Large rodents (up to 20 pounds).
Other rodent families, with common name (if there is one):
Gliridae - dormice Platacanthomyidae - tree mice Spalacidae - Calomyscidae - Nesomyidae - Anomaluridae - scaly-tailed squirrels Ctenodactylidae - “gunids” Petromuridae - dassie rat Thryonomyidae - cane rats Dinomyidae - pacarana Ctenomyidae - tuco-tucos Octodontidae - Abrocomidae - “chinchilla” rats Echimyidae - spiny rats