Pryor Mountain wild horses WE

This entry was contributed to Wild Equus by Dr. Jason Ransom of Colorado State University, member and specialist of the Wild Equus Network (WEN).


Species: Equus caballus

Subspecies/Breed/Type: American mustang

Country: United States of America

Region/Province/Range: Pryor Mountains – Montana

Population type: Semi feral – heavily managed

Estimated Population size: about 150 horses

Management Authority:  Bureau of Land Management

Images by Dr. Jason Ransom. Please respect © copyright!

Management Practices: 

The US Bureau of Land Management has managed this population with periodic round-ups, adopting removed horses to the public. Horses from this population are highly adoptable because many of the animals exhibit genetic relatedness to more primitive Iberian horses and often have primitive markings such as a dorsal stripe, wither bars, and leg bars. Management began using the immunocontraceptive PZP in 2003, combined with periodic removals. Management today is done in partnership with the Pryor Mountain Mustang Center, a non-profit organization dedicated to the well-being of these horses.

For more information and a blog, please see the Pryor Mountain Mustang Center website at http://www.pryormustangs.org/

Details of Population

The Pryor Mountain Wild Horse Range, located in Bighorn County, Wyoming and Carbon County, Montana, USA (latitude 45°04‘N, longitude 108°19‘W), consists of roughly 16,000 ha of low desert, foothill slopes, forested montane slopes, steep canyons, and isolated grassy plateaus. Elevations ranged from 1,175 m to 2,670 m. Vegetation types varied greatly from lower to higher elevations of the range with lower elevations dominated by sagebrush communities, mid elevations dominated by curl-leaf mountain mahogany (Cercocarpus ledifolius) and Utah juniper communities, and high elevations dominated by limber pine (Pinus flexilis), subalpine fir (Abies lasiocarpa), and alpine bluegrass (Poa alpina). Mean annual precipitation is 161.4 mm (range = 96.7–233.4 mm) and mean annual temperature is 7.1°C (range -33.9– 40.0°C). Pumas (Puma concolor) prey on foals somewhat regularly, but rate of depredation varies over time as selected for by individual pumas. Most horses here tend to migrate to higher elevations in the summer as snow melts off of subalpine meadows and then they retreat into the mid-elevations and lower desert in winter. This area was protected for horses prior to the 1971 U.S. law that designated horse ranges thanks to grassroots public interest. That interest remains today and citizens continue to monitor horses and collaborate with researchers and managers toward the stewardship of this herd.

Structure and demographics

A detailed account of demographics from 1996-2003 can be found at: Demography of the Pryor Mountain Wild Horses

This report shows that pooled across years, productivity was 0.501 foals/mare (range = 0.254–0.705) for mares ≥2 years of age, 0.576 foals/mare (range = 0.300–0.795) for mares ≥3 years of age, and 0.597 foals/mare (range = 0.311–0.795) for mares ≥4 years of age. Pooled across years, ages, and sexes (n = 2,531), the annual survival rate of horses on the study area was 0.899.

Population size has ranged over the years from 200 horses, but averages closer to 150. The horses arrange themselves into 29 to 38 bands of 2–11 horses each. Bachelors form loosely associated ephemeral bands or range independently.

Issues worth noting and needed actions

Like most populations in the USA, available habitat for horses is finite and management is necessary to protect all natural resources while attempting to balance the multiple-use mandate for the federal lands where horses live.  The science needed for more-informed management is improving, but many obstacles persist. You can read much more in the 2013 National Research Council report “Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward” Click link to view free PDF.

Bibliography and Further reading

On-going behavior and ecology research from Dr. Ransom can be followed on Twitter @wildequids

McCullough Peaks horses

This entry was contributed to Wild Equus by Dr. Jason Ransom of Colorado State University, member and specialist of the Wild Equus Network (WEN).


Species: Equus caballus

Subspecies/Breed/Type: American Mustang

Country: United States of America

Region/Province/Range: Park County – Wyoming

Population type: Semi feral-heavily managed

Estimated Population size: between 112-194 horses

Management Authority:  Bureau of Land Management -McCullough Peaks HMA

Images by Jason Ransom. Please respect © copyright!

Management Practices: 

The US Bureau of Land Management has managed this population with periodic round-ups, adopting removed horses to the public. Since 2004, management has more intensively been done using a time-released form of the immunocontraceptive PZP and periodic round-ups.

Details of Population

McCullough Peaks Herd Management Area is located Park County, Wyoming, USA (latitude 44°35‘N, longitude 108°40‘W), and consists of 44,400 ha of primarily open sagebrush steppe with badlands along the western edge. Vegetation consists of large expanses of small shrubs, grasses, and forbs. Pronghorn antelope and mule deer are sympatric with horses here and little natural depredation occurs. Elevations range from 1,200 m to 1,964 m. Mean annual temperature is 8.0°C (range -30.0– 37.8°C) and mean total annual precipitation is 271.2 mm (range=168.9–389.1 mm).

Structure and demographics

Population size reached a high of 495 horses before a large management removal in 2004, and now is maintained between 112 and 194 horses. Bands average 8 horses and many bands closely associate into herds; travelling, feeding, and resting together. At its largest population, bands with more than one stallion occurred, but are now infrequent. Bachelors form loosely associated ephemeral bands or range independently. Genetically, these horses are most related to draft breeds such as the Percheron, probably reflecting much of the early settlement activity around the old west town of Cody. Horses of all colors are in this herd, including Overo, Tobiano, and Sabino paint horses.

Issues worth noting and needed actions

Like most populations in the USA, available habitat for horses is finite and management is necessary to protect all natural resources while attempting to balance the multiple-use mandate for the federal lands where horses live.  The science needed for more-informed management is improving, but many obstacles persist. You can read much more in the 2013 National Research Council report “Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward

Bibliography and further reading

Additional details about this population, and specifically about behavior and fertility control, can be found in:

Ransom, J.I., Roelle, J.E., Cade, B.S., Coates-Markle, L., and A.J. Kane. 2011. Foaling rates in feral horses treated with the immunocontraceptive porcine zona pellucida. Wildlife Society Bulletin 35:343-352

Ransom, J.I., Cade, B.S., and N.T. Hobbs. 2010. Influences of immunocontraception on time budgets, social behavior, and body condition in feral horses. Applied Animal Behaviour Science 124:51-60

On-going behavior and ecology research from Dr. Ransom can be followed on Twitter @wildequids

Little Book Cliffs Wild Horses WE

This entry was contributed to Wild Equus by Dr. Jason Ransom of Colorado State University, member and specialist of the Wild Equus Network (WEN).


Species: Equus caballus         Subspecies/Breed/Type: American Mustang

Estimated Population size: between 80–200 horses

Country: United States

Region/Province/Range: Colorado

Population type: Free-ranging-heavily managed

Management Authority: Government Agency – Bureau of Land Management (BLM)

Images from Jason Ransom

Details of Home Range or Territory

The Little Book Cliffs Wild Horse Range, located in Mesa County, Colorado, USA (latitude 39°12‘N, longitude 108°25‘W), consists of approximately 14,600 ha of sloping plateaus, sagebrush (Artemisia spp.) parks, and 4 major canyon systems. Elevations range from 1,500 m to 2,250 m, and the vegetation is characterized by dense stands of Colorado piñon (Pinus edulis) and Utah juniper (Juniperus osteosperma). Mean annual temperature is 11.5°C (range= -26.7– 41.1°C). Mean total annual precipitation is 235.4 mm (range=184.4–300.2 mm) and this typically falls in a monsoonal pattern of late summer rains. Pumas (Puma concolor) are present and do prey on foals, but rarely kill subadult and adult horses. Horses use all aspects of the geography, including travel routes shared with bighorn sheep (Ovis canadensis) on some nearly vertical cliff faces. Most horses tend to migrate to higher elevations in the summer and retreat into the canyons in winter. This area was protected for horses prior to the 1971 U.S. law that protected wild horses thanks to grassroots public interest. That interest remains today and citizens continue to monitor horses and collaborate with researchers and managers toward the stewardship of this herd.

Details of Population

The US Bureau of Land Management has managed this population with periodic round-ups, adopting removed horses to the public. Since 2003, management has more intensively been done using the immunocontraceptive PZP. Prior to PZP use, annual population growth exceeded 20% (in 2003), but between 2004-2011 when PZP was fully implemented, annual growth rate was reduced to an average of 7.6%,  resulting in less frequent round-ups.

Structure and demographics

Population size ranges from 80–200 horses and is arranged into roughly 30 bands of 2–9 horses each. Bachelors form loosely associated ephemeral bands or range independently. Most females give birth within about a 4 week time period ranging from late April to late May.

Issues worth noting and needed actions

Like most populations in the USA, available habitat for horses is finite and management is necessary to protect all natural resources while attempting to balance the multiple-use mandate for the federal lands where horses live.  The science needed for more-informed management is improving, but many obstacles persist. You can read much more in the 2013 National Research Council report “Using Science to Improve the BLM Wild Horse and Burro Program: A Way Forward”  – a free PDF is available at http://www.nap.edu/catalog/13511/using-science-to-improve-the-blm-wild-horse-and-burro-program


Additional details about this population, and specifically about behavior and fertility control, can be found in:

Ransom, J.I., Roelle, J.E., Cade, B.S., Coates-Markle, L., and A.J. Kane. 2011. Foaling rates in feral horses treated with the immunocontraceptive porcine zona pellucida. Wildlife Society Bulletin 35:343-352

Ransom, J.I., Cade, B.S., and N.T. Hobbs. 2010. Influences of immunocontraception on time budgets, social behavior, and body condition in feral horses. Applied Animal Behaviour Science 124:51-60

Ransom, J.I., Hobbs, N.T., and J. Bruemmer. 2013. Contraception can lead to trophic asynchrony between birth pulse and resources. PLoS ONE 8:e54972

Theodore Roosevelt free-ranging horses WE

This entry was contributed to Wild Equus by Dr. Jason Ransom of Colorado State University, member and specialist of the Wild Equus Network (WEN).


Species: Equus caballus         Subspecies/Breed/Type: American Mustang

Estimated Population size: Maintained at 120–160 horses

Country: United States

Region/Province/Range: Theodore Roosevelt National Park

Population type: Free-ranging-heavily managed

Management Authority: Government Agency – National Park Service

Images from Jason Ransom

Details of Home Range or Territory

Theodore Roosevelt National Park is located in south-western North Dakota, USA (45◦55’N/103◦31’W). The South Unit of the park, where horses range, is approximately 19,000 ha and consists of eroded badlands with gullies and ravines separated by large upland plateaus, and small buttes. The mixed-grass prairie vegetation is predominantly comprised of needle and thread (Hesperostipa comata), threadleaf sedge (Carex filifolia), western wheatgrass (Pascopyrum smithia),blue grama (Bouteloua gracilis) and little bluestem (Andropogen scoparius). Unlike most mustangs in the US, which are managed by the Bureau of Land Management, this herd is part of the National Park Service system. Horses in the park are preserved as part of the cultural landscape, but because they range with pronghorn (Antilocapra americana), bison (Bison bison), mule deer (Odocoileus hemionus) and elk, the result is a vignette of primitive North American landscape.

Details of Population

Details about the park and its resources can be found at www.nps.gov/thro. Research is on-going for this population and longer-term behavioral data are currently being analyzed. Additional details about this population, and specifically about behavior, can be found in: Ransom, J.I., Powers, J.G., Garbe, H.M., Oehler Sr., M.W., ,Nett, T.M., and D.L. Baker. 2014. Behavior of feral horses in response to culling and GnRH immunocontraception. Applied Animal Behaviour Science 157:81-92

Structure and demographics

This population is maintained at around 120–160 horses through periodic management removals and immunocontraception (GnRH). Predation by pumas is minimal, even though the large cats share habitat. The horses organize themselves into about 20 bands with an average band size of about 8.7. All individual horses in this population are identified and assigned individual identity numbers by managers and researchers, and age and reproductive data for each animal are maintained.

Issues worth noting and needed actions

Like most populations in the USA, available habitat for horses is finite and management is necessary to protect the full suite of natural resources in this National Park.  The on-going research on use of GnRH to reduce fertility is promising as it appears to have minimal effects on short-term behavior while slowing population growth. Like all management tools, the long-term effects of human actions need to be monitored in order to responsibly preserve the ecosystem.

Gower ponies WE

We would like to thank Equine behaviourist Jennie Nellist for this entry of the ponies living on the Gower Peninsula, Wales.


Species: Equus caballus

Subspecies/Breed/Type Gower ponies

Country: United Kingdom

Region/Province/Range: Gower, Swansea

Population type: Free-ranging-heavily managed

Estimated Population size: over 250 horses

Images by Jennie Nellist

Details of Population

The Gower Peninsula contains a total of 50 square kilometers of common land, split into many smaller parcels, most of which are grazed by ponies and horses. From salt marsh and sand dunes of North Gower,  heath land of Rhossili Down, the brown stone ridge and sink holes of Cefn Bryn, to the acidic moors of Welsh Moor, Pengwern, Fairwood and Clyne, Gower’s textbook fame for its remarkable geology makes sure there’s  surprising variety of habitat in an area only 19 miles long. See also.

Structure and demographics

Each common varies as to the number of ponies or horses, as well as their type or breed, sex ratio and the presence of foals and juveniles. Typically Welsh Mountain ponies are seen, with a number of active Hill Pony Improvement Societies in place – with ponies being registered with the Welsh Pony and Cob Society. There are also other Welsh ponies and cobs, cobs, cross breeds, Irish Draft horses and Shire and Shire crosses grazed on Gower commons. Some ponies are not used for breeding, are bred on private land and mares are returned to the common to give birth to and rear their young. Other scenarios include temporary turnout of a stallion over the spring and summer breeding season. Stallions may also be turned out all year round. Stallions are also abandoned by owners without common grazing rights. Over all, the population is mostly mares with geldings and stallions in the minority (tens compared to hundreds)

Issues worth noting and needed actions

There is an on going problem with abandonment of equines across the Swansea area and wider South Wales.

Further reading

Gower Commons Ponies


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