FAQs

What is the Foster Horse Program?
The Foster A Horse Program was crated in an effort to preserve one of America's most loved wildlife treasures.  To learn more about the program, please click here!
What does my donation support?
All funds raised by Assateague Island Alliance directly benefit Assateague Island National Seashore.  AIA provides supplies, services and materials to operate and manage the following programs: Foster Horse program which helps fund the wild horse management program and includes genetic testing, pregnancy testing, educational outreach as well as administering pzp.  In 2018, AIA offered 27 health and wellness programs to enhance the National Park Service’s call to action campaign to increase those opportunities for visitors in National Parks.  In addition AIA provided 16 Lifelong Learning programs, the Assateague Artist is Residence program and 4 Artists Workshops.  We are so very grateful for all donations, big and small, that allow us to continue to grow the great work we do.   In the fall of 2017 AIA and the National Seashore launched "A Fed Horse is a Dead Horse" A project to protect Assateague's wild horses that includes three strategies to keep human and pet food inaccessible to horses.  The three strategies include replacing all picnic tables with tables that house horse proof boxes, purchase and distribution cooler straps to visitors, and an interpretive rack card educating visitors of the dangers of allowing horses to access any food that is not the their natural forage.  In 2018 AIA was awarded the 2019 Non-capital match grant through the Maryland Heritage Area Authority in the amount of $50,000 for "A Fed Horse is a Dead Horse" and since 2016 the majority of our fundraising efforts have been working toward matching their $50,000 contribution.  This is a huge accomplishment for our small organization!  Cooler straps were purchased in January 2019, Picnic table frames were purchased and delivered in June 2019 for construction this summer.  Cooler box supplies and materials are to follow as funding allows.  The project completion date is December 31, 2019.   In addition, each year the National Park Service presents AIA with a wish list of supplies, programs and equipment and AIA attempts to respond accordingly through either direct purchase or an appropriate donation to Assateague Island National Seashore.   Funds donated to the Foster Horse program will help to maintain a healthy horse population and preserve their naturally social behaviors. To learn more about the program, please click here!
Can more than one person foster the same horse?
Yes.
How long does my participation in the foster horse program last?
One year or you can renew for the life of your horse.
What is the wild horse management program?
What are safe practices for viewing the horses?
How Horses Adapt to Winter
Left to adapt to their environment, Assateague horses must create their own protection, and a horse’s winter coat is a remarkably protective feature. The coat starts to grow long before the cold days of winter. As the days began to shorten and the retinas received fewer hours of sunlight each day, the brain is stimulated to release extra melatonin, a hormone that prompts the hair follicles to produce more hair. You may notice that the horses’ winter coats appear to be fluffy. This is because the hairs lift up to trap warm air, creating insulation, much like a bird creates insulation by fluffing its feathers. Even more incredible…the long outer hairs form channels that help repel water. And if you separate those hairs, underneath there is a layer of dry hair and skin. Pretty Amazing!
Why do foals sometimes have a mask like Batman or Batgirl?
People often ask if there is something wrong with the foals when they have mostly black hair around their eyes, wondering if they have a skin condition based on their appearance. So why do they have those rings around their eyes and muzzle? Rest assured, no skin condition. They are shedding the soft and fluffy foal coat, and the new, sleek adult coat is darker and smoother. They shed around the eyes and muzzle first, and gradually the rest of it will be replaced.
What’s a Kieper Number?
Every horse in the Maryland herd is given an alphanumeric code, such as those of the horses pictures here from left N6BM, N6BMT (Sonja), N10O (Tipperary), N6BMT-F (Jojo) and N6BMT-FO (Margaret’s Thunder Heart).  This image was taken in 2017 and includes four generations!   Notice anything about their codes?  Maternal lineage is just one thing you can discover by looking closely at the horses alphanumeric code. When researcher Dr. Ronald Keiper began studying the Assateague horses in 1975, he developed a system that could identify, and trace the maternal ancestry of, each individual horse. The system of alpha-numeric identification numbers he came up with are now known as "Keiper numbers" In 1975, there were only 44 horses in three harem bands living on the Maryland portion of Assateague Island. A harem band consists of a dominant stallion and his mares and immature offspring. Each of these bands was designated by the letter M, N or T. The dominant stallion of each band was given the number 1, resulting in Keiper numbers M1, N1 and T1 for the stallions. The other horses in each band were numbered consecutively beginning with 2 (M2, M3, T2, etc.). The letters at the end of each horse’s number indicate that particular individual's maternal lineage and their birth years back to the original 1975 study horses. At birth, each horse is assigned a Keiper number created by adding the letter for its birth year to its mother's Keiper number. Birth years began in 1976 with A, B for foals born in 1977, C for 1978, up through Z in 2001. At that point the alphabet was started over with a dash in front of the letter, resulting in -A for foals born in 2002. Accordingly, N6BMT-FN was born in 2015 to N6BMT-F; N6BMT-F was born in 2007 to N6BMT; N6BMT was born in 1995 to N6BM; N6BM was born in 1988 to N6B; N6B was born in 1977 to N6. N6 was present in the herd during the initial 1975 survey and so does not have a birth year letter. She was the sixth horse identified in "N" herd. And the "X" horses? During the 1980s, birth records for the herd were not as closely maintained as they are today. By 1990, there were about 25 unidentified, mostly solid-colored horses living on the island that had been born in the mid-1980s. These horses were designated with an "X" and numbered consecutively. Following a complete genetic study of the horses in 2005, correct identification and parentage for most of these “X” horses were determined based on their genotypes. An example is the mare X13, who was confirmed as being N2BH. Five of these “X” horses could not be positively identified, and so they retained their “X” IDs. However, presumed offspring of the “X” mares living at the time of the genetic study were confirmed as descending from these “X” mares, and so were named according to the same protocol as all of the positively identified horses. The stallion X15NY, for example, was born to X15N in 2000; X15N was born in 1989 to X15, who was one of the five “X” individuals living in 2005 who could not be positively identified. A 1976 B 1977 C 1978 D 1979 E 1980 F 1981 G 1982 H 1983 I 1984 J 1985 K 1986 L 1987 M 1988 N 1989 O 1990 P 1991 Q 1992 R 1993 S 1994 T 1995 U 1996 V 1997 W 1998 X 1999 Y 2000 Z 2001 -A 2002 -B 2003 -C 2004 -D 2005 -E 2006 -F 2007 -G 2008 -H 2009 -I 2010 -J 2011 -K 2012 -L 2013 -M 2014 -N 2015 -O 2016 -P 2017 -Q 2018 -R 2019 -S 2020
Where can the horses be found?

The Assateague Island National Seashore Horse Location Guide, seen here, is to help you identify the various bands on the island, each usually found according to the Stallion. Note that bands often change due to “Stallion Wars,” mares roaming and, well, Mother Nature. To see photos of the horses, please download the AIA Horse ID app. We are in the process of updating the app frequently to help you with identification and will update this page, as well!

This information has been updated as of July 1, 2019

Always remember to keep 40 feet or more away from the horses (length of a bus) and do NOT feed or pet them. If they approach you, move away. Help us keep them wild, will you?

Northern End of the Island

(Often around 2.5 – 7 km)

Chestnut,M6MS-G (Sorrel Pinto Stallion with white mark on right side); Born 2008

Bonnie.T6K-A (Dark Pinto Mare with marking on her left side); Born 2002

Freedom,M2EINS (Sorrel Mare with strip and snip and a flaxen mane); Born 1994

Little Paka, M17GMV (Sorrel Mare with an offset tiny star and right mane); Born 1997

Rohan, M2EINR-B (Sorrel Mare with tiny star, light backs of hindquarters, left mane); Born 2003

Shasta,N2BHS-J (Sorrel Mare with large white star on forehead); Born 2011

Josie Rue, N2BHS-JQ (Pinto Filly); Born 2018

North End above State Park

(Usually can be seen along the bay side across from Casataway’s Campground)

Patches,T3DMY, is a Chestnut Stallion with a long white marking on his right side; Born 2000

Northern Developed Area of State Park

(Sometimes found along causeway. Please “yield to the horses” and drive slowly.)

Yankee, N9BM-E (Pinto Harem Stallion with white stripe in tail); Born 2006

Eve, N2BHS-E (Dark Bay mare that hangs in the northern end); Born 2006

Gokey GoGo Bones, N2BHS-A (Chestnut Mare with left hind white sock and hoof, hazy eyes); Born 2002

Lauren’s Laughter, N6BIRUY (Bay Mare w/sloping narrower hip than usual; a bit of a “yellower” color); Born 2000

Patricia Irene,N2BHS-H (Bay Pinto Mare w/white marking on neck /white socks); Born 2009

Chantilly Lace or Lacey, N2BHS-AR (Born May 2019)

Developed Area, National Park

Joy, N2BHS-AG (Chestnut Harem Stallion with tiny pink snip in between nostrils; Right mane); Born 2008

Sarah’s Sweet Tea, N2BHS-O (Unmarked, Sorrel yearling Bachelor Stallion); Born 2016

Ms. Macky, N2BHS-AL (Pinto bay mare with four white socks); Born 2013

N2BHS-ALR (Ms. Macky's foal); Pinto; Born June 2019

Connie’s Girl, N2BHS-ALQ (Unmarked Sorrel filly); Born in April 2018

Developed Area, North Beach & Oceanside Campground

Delegate’s Pride(nicknamed “Chip”), N6ELS-H (Dark Bay Harem Stallion with tiny star on forehead); Born 2009

April Star, N2BHS-C (Pinto Mare with star on her forehead; front legs are white); Born 2004

Ronni, N2BR, (Small star, right mane); Born 1993

Susi Solé,N2BHS-M (Pinto Mare with all white legs and circle on mid-back); Born 2014

Seases Bay Breeze or "Breezy", N2BHS-MR (Pinto filly); Born in January 2019

Something Special, N9BFNS-E (Sorrel mare with small star, pink snip, white hind socks); Born 2006

Developed Area, Bayside Campground and Ferry’s Landing

Corky,X15NY (Sorrel Harem Stallion, who is stocky with small, offset white mark above right nostril – about the size of a pinky finger; right mane); Born 2000

Johnny’s Star, N2BHS-CK (Pinto Mare, predominantly white with brown spot on middle back with point. Looks like a conversation bubble); Born 2012

Moonshadow, N2BHS-CKP (Sorrel filly with white hind hooves and socks); Born 2017

Oversand Vehicle (OSV) Entrance to 7 -18 km / Tingles Island

Bodacious Bob, M6MSY (Medicine Hat Bay Pinto Harem Stallion); Born 2000

Giggles, N9BM-J (Sorrel Mare, unmarked with distinctly hazy right eye from old injury; light colored mane); Born 2011

N9BMT-JO, nicknamed “Happy” as the person who purchased naming rights has not yet named him (Sorrel, stallion); Born 2016

Billy Bob,N9BM-JQ (Pinto colt), Born 2018

OSV 18 - 20 km/Tingles Island area

South Developed area during the summer

Fonzi, N9BFNSZ (Sorrel Harem Stallion with long forelock that covers his star. White left front sock and striped hoof; right mane); Born 2001

Bright Star, N6BIRU (Sorrel mare with narrow white blaze, white hind stockings and flaxen mane); Born 1996

Linda Rae’s Autumn Glory, N2BHS-AP (Sorrel Pinto filly with black mane, predominant white markings including a white tail that is black at bottom); Born 2017

 

OSV 18 -19 km

Bayberry, N6BIR-B (Dark Bay Harem Stallion with very long, wavy mane and tail). Born 2003

Aliyana Grace, N6ELS (Sorrel, Pinto mare with blond mane, mostly white body); Born 1994

Precious, T6M(Bay Pinto mare w/white mane and tail); Born 1988

Pretty Lass, N2BHS-BJ (Bay Pinto mare); Born 2011

Miss Priss, M2EINR (Sorrel mare with a white star); Born 1993

Maggie, N6EM (Bay Pinto mare); Born 1988

Little Dipper, N2BHS-B (Sorrel mare with a few white hairs on her forehead); Born 2003

Silver Spurs Island Mist, M6IX (Sorrel mare with a long, narrow, upside-down teardrop shaped star); Born 1999

Spirit, N9BFNS (Sorrel mare, darker than most, mane mostly right); Born 1994

Queen, N9BFT(Bay Mare with refined face, split mane); Born 1995

(OSV 23 – 27 km

Developed area in the summer)

Assateague Lightning, N6BMT-I (Bay Pinto Harem Stallion pinto with lightning mark on left shoulder and Z mark on right rump. Some now refer to this as his “Harry Potter” marking); Born 2010

Bella-Boo, N6EMSZ (Bay mare); Born 2001

April, T6CHU(Bay Pinto mare); Born 1996

Bailey, N9BFQX (Chestnut mare with a small comma-shaped star and white left hind hoof and sock); Born 1999

Coco, T3DHT (Buckskin mare, only one on record for MD herd); Born 1995

Gizmo, T3DHT-H (Bay mare who is shorter than most MD horses); Born 2009

Harmony, N9BFQ-G(Sorrel mare with left hind sock, left mane); Born 2008

Marina(sorrel with short, thin, white blaze). Born 2005

Tommy ThunderBolt Nektosha, N9BFQ-GP (Sorrel stallion); Born 2017

 

OSV 20-21 km (Little Levels area)

Often in the developed area in the summer

General Harker,X16-A (Sorrel Harem Stallion, unmarked, lighter, less red, right mane); Born 1994

Alexandria’s Angel, N9BFT-KP (Sorrel mare); Born 2017

Assateague’s Phoenix, N10T-JO (Sorrel pinto Colt w/white marking near his withers); Born 2016 (Phoenix has been "band" hopping of late. Next time he is located, we will post)

BJ, N10R (Sorrel Pinto mare); Born 1993

Jojo, N6BMT-F (Sorrel w/tiny star who has a tendency to wander off on her own); Born 2007

Ninka, N10T (Palomino Pinto) Born 1993

Princess Minja Shunka, N6BIR (Pinto mare with white left front leg); Born 1993

Rosie, M6MS (Bay Pinto mare with faint spots, looking like freckles on her body); Born 1994

Theodore, N6BMT-FQ (Sorrel colt who wanders off with mother Jojo); Born 2018

OSV 23 - 27 km

Often in developed area during summer

Mr. Frisky Hooves, N9BFQ-GL (Sorrel Harem Stallion with white left hind hoof and sock); Born 2013

Annie Laurie, N2BHS-I(Sorrel Pinto Mare with predominantly white butt); Born 2010

Christina Key, M2EIQ (Chestnut mare with dagger-shaped blaze and white hind hooves and socks); Born 1992

Mieke’s Noelani, N2BHS-AIO (Sorrel filly with tiny white star); Born 2016

Tara, T5AR (Sorrel mare with a bit more red, longer mane, often tangled); Born 1993

OSV 23 to km 28

Charcoal, N9BNZ (Only black Harem Stallion on the island); Born 2001

Tipperary,N100 (Sorrel Pinto mare; Tipperary looks as if she has an English saddle on her left side. Light colored mane near withers); Born 1990

Sonja, N6BMT (Bay Pinto Mare with four white stockings, black mane and black tail); Born 1995

OSV 31 – 33 km to State Line

(Most often in the marshes)

Dewey, N100-J (Bay Pinto, Blue-Eyed Harem Stallion); Born 2011

 Chica Linda, N9BFV (Sorrel mare); Born 1997

Sapphire, T3DH-D (Bay mare); Born 2005

Sienna Belle, N9BO-A (Chestnut mare with dusty white triangular star); Born 2002

OSV – 33 km to MD/VA state line

Foxy’s Gift, N6BKOS-H (Sorrel Stallion w/star and white hind hoof and half-sock); Born 2009

Lion’s Mane, N6BP (Sorrel Mare with/white, wide blaze and light mane); Born 1991

 
How do the horses weather a storm?
Whenever severe weather threatens Assateague Island National Seashore, we inevitably get asked the question "how will the horses survive the storm?". Generally, the Assateague Horses retreat from the developed areas of the park to spend the cooler months in the bayside marshes where their preferred forage, Spartina alterniflora (Saltmarsh Cordgrass), grows abundantly. And what in the world do they do when a hurricane or nor'easter strikes? Believe it or not, it's not such a big deal to them (especially when compared to the heat, drought andinsects they have to deal with in the summer). During extreme weather conditions they find shelter from high winds and storms by temporarily retreating from the marshes to forested or densely vegetated areas and turning their tails to the wind.  
Help us keep ’em Wild!
Whether you are visiting the island for a short or long visit, we ask for your help in keeping our horses wild.  We encourage you to view the video about the horses and why we ask you to keep your distance.  Take three minutes and watch our Keep 'Em Wild video Remember . . .
  1. Maintain a distance of 40 feet or more. If a horse approaches you, back away.
  2. The park does not advocate your taking initiative in trying to move the horses.  Trying to get them away from your campsite should be left to the rangers and other park staff who have specialized training in wild horse management practices. (If you respond, "I have horses and know what to do" that does NOT mean that you have permission to interact with them in any way). Remember, it's a park law to keep you distance.
  3. Drive slowly and safely. Remain alert. Horses and deer often run into the road, particularly if spooked. Let's have a year with no animals being hit by a vehicle.
  4. Enjoy the park and PLEASE help us keep the horses wild.
Apples and carrots are NOT a treat on the island

While you may think you are giving the Wild horses a treat with apples and carrots, in reality, this is not part of their diet and can lead to a very painful death.

During the winter, the park staff and volunteers find people leaving apples and carrots for the horses, because they "think they are hungry." Unfortunately, these apples can kill a wild horse with colic quickly. Additionally, it teaches the horse bad behaviors, looking toward humans for food, which leads to them hanging out and raiding campsites and "hanging in traffic" (again, leading to possible death). Sadly, Assateague Island National Seashore has had wild horses die for the very reasons listed, eating food other than salt marsh grass and being in the road.

A reminder that feeding a horse and/or approaching to within 40 feet of the wild animal is against the law and you can be fined. Even if you are "familiar" with horses and have them on a farm, it doesn't mean that you are allowed to approach them. Help us keep them wild, will you? If you need more information, please watch the video "Keep 'em Wild."  Please!!! If you see something, say something. 410.629.6603
Curious about Swamp Cancer or Pythiosis?
Many of our Assateague Friends have raised the question about the fungal infection, Pythiosis or "swamp cancer” (not really cancer) in the Maryland herd. There have been no signs of the disease in the Maryland herd and Resource Management staff consistently monitors the horses for any signs and symptoms. Pythiosis thrives in stagnant pools of fresh water and is a naturally occurring pathogen. You may be aware that the two herds of horses are managed very differently on Assateague Island. The Maryland herd is free to roam the entire Maryland section of Assateague and they are able to access many varied sources of fresh water in the back country.  Of note is that many of the freshwater ponds in MD often get surrounded by salt water, thereby potentially minimizing the overall risk of phythiosis. There are approximately 42 ponds on the Maryland portion of Assateague Island, and during a rainy period there are countless ephemeral pools. That is where the feral horses find their water year-round, as well as every other type of wildlife. That plus the smaller size of the MD herd both attribute to a much less hospitable environment for swamp cancer. The Chincoteague ponies are kept in grazing compartments on the Virginia portion of Assateague and there is a physical fence at the state line to prevent the two herds from coming in contact.
 
The National Park service is constantly monitoring the horse population and the horses are managed as a wild herd. If you have questions about this or other items, we encourage you to reach out directly to the Assateague Island National Seashore team.  https://www.nps.gov/aboutus/contactus.htm
 
Where do the wild horses find water on the island?
There are approximately 42 ponds on the Maryland portion of Assateague Island, and during a rainy period there are countless ephemeral pools. That is where the wild horses find their water year-round, as well as every other type of wildlife. During the summer, well-meaning visitors often turn on a spigot to give the horses water. Please call a ranger if you see this happening. Again, while one thinks they are doing the horse a favor, it contributes to changing their behavior in a negative way. Often, horses trying to get access to the "free drink" become aggressive, kicking and biting each other and, quite possibly, a human trying to “help them out.” The wild horses do quite well on the island without human intervention, surviving for well over 300 years. Help us keep them wild, will you?
Is a horse pregnant or not?
Each November, Assateague Island National Seashore biologists conduct pregnancy tests on the mares among the population of wild horses on the barrier island in an attempt to predict how many, if any, new foals are expected to join the herd in the coming year. Essentially, staffers follow the mares and wait for them to defecate. Samples are collected, frozen and sent to a lab to be analyzed to determine if any of the mares will be expecting next spring. Of course, there could be a surprise or two. For example, in 2019, Susi Solé (N2BHS-M) gave birth to N2BHS-MR (Seases Bay Breeze or "Breezy") in January and it was a complete surprise (albeit, her tummy was very, very round).
Horses or Ponies – Here’s what Natl. Seashore Believes
You may notice that the wild horses on Assateague Island National Seashore are often referred to as “ponies” by some. There is even some signage at the State Park that says “ponies.” That being said, the National Seashore refers to them as horses.   Here’s why: The short answer is that they are most closely related to horse breeds than pony breeds. Although anything less than 14.2 hands (a "hand" is 4", and equines are measured to the top of the shoulder) is generally considered a pony (and the Assateague horses are 12-13 hands), yet, there are many, many exceptions. Here are a few examples: Arabians are often less than 14.2, miniature horses are very tiny, and Caspian horses are 12-13 hands similar to Assateague horses, but they are all still horse breeds.  And on the other side, Connemara ponies are often more than 14.2 hands, but are still a pony breed.   According to the National Park Service, the horses might grow a little taller under domestic conditions (maybe a couple inches), but not up to full horse size of over 14.2 hands. Many breeds of horses and ponies have been turned out on the island for hundreds of years, and, in time many, were left to go feral. The smaller type we see now is what has adapted best to the conditions on the island and to the available forage, surviving and thriving over the years. Genetically they are a smaller animal. Call them horses or ponies, but remember that they are wild and we need your help in keeping them that way by not feeding them, not petting them, moving away from them if they approach you, keeping a distance of at least 40 feet. Every interaction makes a difference!   If you see someone breaking the law or doing things that prevent these horses from remaining wild, please contact the ranger station at 410.641.1441
  • At the first prompt, choose '3'.  That option directs the caller to the visitor contact station.
  • At the second prompt, there are several options:
- option #2:  law enforcement offices - option #1:  front desk - option #0:  operator (business hours; reverts to front desk on the weekends) Keep in mind that these numbers are staffed intermittently throughout the day; there is no guarantee that a call will be answered due to a variety of factors.
The Story Behind Carol’s Girl (N2BHS)
CAROL’S GIRL (N2BHS): MATRIARCH OF AN ISLAND DYNASTY The Habsburgs, the Medicis, the Plantagenets, the Kennedys, and, of course, the Carringtons.  And, now, Assateague Island’s N2BHS dynasty. The past several years have seen a number of new foals arriving on Assateague Island, and you may have noticed that many of them have something in common: their parentage and their Kieper numbers. First, a word about Kieper numbers:  these are the alphanumeric designations the National Park Service uses to identify the wild horses. Kieper numbers – a system developed by Dr. Ronald Kieper – combine a horses’s dam’s identity with the year the horse is born (“dam” is equine lingo for “mom”). Let’s take N2BHS-A Gokey GoGo Bones as an example.  The last characters of her Kieper number are “–A” which tells us she was born in 2002. The characters ahead of that tell us that her dam was N2BHS Carol’s Girl.  Likewise, the “S” in Carol’s Girl’s Kieper number tips us off that she was born in 1994 to the mare N2BH (known as “VIP”). And so on. Why the dash in Gokey’s birth year character?  Well, 26 years after beginning to use this system we ran out of letters when we reached the “Z” in 2001, and had to start at the beginning of the alphabet again – so this identification system simply adds the dash to avoid confusion! But back to the island’s youngest generation.  Let’s look back through 2016. 2016:  N9BM-JO a.k.a. Happy, N6BMT-FO Margaret’s Thunder Heart, N10T-JO Assateague’s Phoenix, N2BHS-O Sarah’s Sweet Tea, N2BHS-AIO Mieke’s Noe’Lani, and N2BHS-AO Adriana’s Yankee Prince 2017:  N2BHS-AP Linda Rae’s Autumn Glory, N2BHS-CKP Moonshadow, N9BFQ-GP Tommy Thunderbolt Nektosha, and N9BFT-KP Alexandria’s Angel 2018:  N2BHS-ALQ Connie’s Girl, N9BM-JQ Billy Bob, N2BHS-JQ Josie Rue, and N6BMT-FQ Theodore 2019:  N2BHS-MR Seases Bay Breeze, N2BHS-AR Chantilly Lace, and N2BHS-ALR Notice how many times N2BHS appears in that list?  N2BHS was the mare Carol’s Girl, and these are her descendants.  Carol’s Girl, who died in 2017, is the only mare who did not respond to the immunocontraceptive PZP that NPS has used with the island’s mares since 1994 to control fertility and herd size. So while most of the other mares on the island have had only one foal, or very few foals, with this quite effective system, Carol’s Girl continued to reproduce, with a notable twelve offspring.  They include: N2BHSV Bec’s Orion N2BHSX Jester N2BHS-A Gokey GoGo Bones N2BHS-B Little Dipper N2BHS-C April Star N2BHS-E Eve N2BHS-H Patricia Irene N2BHS-I Annie Laurie N2BHS-J Shasta N2BHS-K N2BHS-M Susi Sole N2BHS-O Sarah’s Sweet Tea So did Carol’s Girl pass her lack of response to PZP on to her daughters and granddaughters?  Apparently not, fortunately!  Seven of her eight daughters were successfully treated for from one to three years before each was removed from treatments to allow foaling. Her first four granddaughters were born early enough to be included in the contraceptive program, and they also were successfully treated for from one to three years.  The only exception to fully successful contraception in Carol’s Girl’s descendants is her first daughter, N2BHS-A Gokey GoGo Bones.  She has produced six foals up through 2019, but only two of them were conceived while she was being treated with PZP. The other four foals were produced while she was not receiving the contraceptive.  PZP is highly effective in preventing pregnancy, averaging about 95%. However, because it is not 100%, in some mares such as Gokey, it has been partially to mostly effective. Biologists who study PZP’s effectiveness note that this treatment, when administered for three consecutive years according to the initial protocol for Assateague’s horses, does not render mares permanently infertile.  When treatment ceases, about 60% recover fertility in the first three years.  Although one mare finally foaled after 10 years (N10R B.J.), most will foal much sooner than 10 years post-treatment. And what does it mean now that N2BHS descendants represent a quarter of the island’s horse population?  NPS is keeping a close eye on the genetic diversity of the herd with the goal of avoiding future health and viability issues that can arise from a population that becomes too closely related.  Removing members of the N2BHS line is not on the table at all, but there are other genetic management options.  These may include leaving non-N2BHS mares uncontracepted when the population size increases enough that the program needs to resume, or introducing new horses from other similar barrier island habitats to add new genetics to the herd. You can begin to understand the familial relationships among Assateague’s younger generations if you use their Kieper numbers to map siblings, cousins, aunts, and uncles. AIA’s mobile app and the Foster Horse program listing are both great resources for learning the Kieper numbers of the horses you encounter on the island. Thanks to Jen Britton for writing this article and to Allison Turner, Biological Technician at Assateague Island National Seashore, for fact checking! For more information about Kieper numbers, read our FAQ.

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