The NPS lists 67 species of mammals living in Yellowstone National Park but they don’t include humans. On the other hand, they also include a few who apparently might not be there. The charismatic megafauna get park population estimates but the rest just get an adjective or two and I’m not sure exactly what the relationship is between rare, uncommon, and occasional which are three of the population estimates. Most of these are from January 2010 but I’ve updated a couple for which I’ve heard more recent estimates. If a range was given, I picked a number in the middle.
Cougar 20 The population center for cougars in the park is on the northern range, especially the Black Canyon of the Yellowstone River. That’s just a few miles northeast of Mammoth, but I haven’t hiked there or seen a cougar yet.
Grey Wolf 100 This is an updated current number, about 15% lower than the previous year’s estimate. The wolf population has declined due to outbreaks of distemper and mange, declining elk population, and wolf-caused fatalities. I recently learned that in 2009 a pack had a den less than mile from Mammoth and they were regularly chasing elk in the developed area until they were harassed into moving. I hope to find the den site when I return. Lamar Valley is the famous spot for wolf-watching but they live throughout the park.
Grizzly Bear 150 Their population has increased over the past 25 years but there could be trouble on the horizon for the grizzly population and more grizzly-human interactions as some of the bears’ important foods are threatened: cutthroat trout by nonnative lake trout and whirling disease; whitebark pine nuts by beetles, blister rust, and climate change; and army cutworm moths by pesticides. Grizzlies do now frequently get free meals by taking over carcasses after wolves have done all the work. On my first day in the park, I saw a sow with four cubs a few miles south of Mammoth. Grizzlies live throughout the park but at various times specific areas are closed to humans because of bear activity.
Moose Less than 200. Moose population dropped in the aftermath of the 1988 fires and because of habitat destruction and hunting outside the park. I haven’t seen one yet.
Mountain Goat 200 A nonnative species which has moved into northern areas of the park. I've seen a few near Tower.
Pronghorn 200 Similar to the more well-known bison history, an estimated 35 million of these critters were once running around the countryside. And like most other large species in the park, they were once killed by park management because they were considered too numerous. Now they are designated as a species of special concern because of declining population. Something about their appearance makes them look to me like they belong on a different continent.
Bighorn Sheep 260 Another species which lives in the northern part of the park and close to Mammoth. I’ve had a close encounter with females and lambs near Tower but not with the bighorns with big horns. Population is slowly increasing after disease greatly reduced their numbers thirty years ago.
Beaver 750 Can be found throughout the park, but I haven’t seen one yet.
Mule Deer 2400 in the summer, most migrate out of the park in the winter.
Bison 3900 This is the estimate from the 2010 summer. Bison population varies widely because of frequent policy changes and mass killings by various state and federal agencies and individuals when they leave the park in the winter. The book I recently quoted provides an excellent look at bison-related issues such as brucellosis, ranchers, hunters, Indians, politics, snowmobiles, groomed winter roads, cattle, tourists, elk, wolves, and grizzlies, but five more years of changes have happened since publication and are ongoing.
Elk 15000 summer, much lower in winter. Another long-time controversial species among people who like to manage wildlife. Too many, too few. A few days ago, a new low count of the northern herd was released causing a new round of wolf hatred although wolves are considered to be just one of the factors in the decline. Elk have been far more likely to infect cattle with brucellosis than bison, but no one calls for killing or quarantining all the elk in the park because lots of people like to kill them outside of the park.
The rest of the critters are just listed in categories.
Badger Habitat is listed as sagebrush so they must be in the Mammoth area but I haven’t seen one. Have seen large trailside burrows which I assumed were from coyotes, but I might have been wrong about that. Something else to ask about when I get back.
Big Brown Bat
Black Bear Primarily in northern parts of the park, often seen in the Mammoth area.
Coyote Population declined after wolves were reintroduced in 1995 which is believed to have increased rodent numbers which then provided more meals to raptors, foxes, etcetera, but coyotes have since adjusted to the presence of wolves. A coyote and I stood about four feet apart staring at each other behind the Mammoth hotel and I’ve listened to their group songs while in my dorm room.
Golden-mantled Ground Squirrel
Human My own category rating on this one. Like elk, far more numerous in the summer.
Little Brown Bat
Montane Vole Considered the most important prey species in the park, but I think it depends on who’s doing the eating.
Northern Pocket Gopher
Pika Likely headed for trouble due to rising temperatures which they can’t tolerate.
River Otter Haven’t seen one in the park yet, but recently saw some photos of one facing off with a coyote.
Uinta Ground Squirrel My companions around the dorm. Between avoiding heat and cold, they’re underground most of the year, but I’ve read that, for unknown reasons, they’re sometimes active in winter at Mammoth.
Yellow Pine Chipmunk
Townsend's Big-eared Bat
Northern Flying Squirrel
Western Jumping Mouse
Wolverine A few of these reclusive animals have been spotted in eastern parts of the park over the years. Climate change resulting in diminishing snow pack is enough of a threat that the government says they should be on the endangered list but there isn't enough money to list them.
RARE, IF PRESENT
Western Small-footed Bat