The Extinct Horses of Canada and How to Bring them Back

North America is the birthplace of the equids. Until the early Miocene, it was the only place in the world where they could be found. Until approximately twelve thousand years ago, horses of the modern Equus  genus, today represented by asses, zebras, and domestic horses, could still be found across North America. Many species have been described based on fossil evidence, but it is commonly thought that there were possibly only two separate species, the horse-like equids, and the stilt-legged or ass-like equids. Each of these may have had many subspecies or ecotypes leading to much taxonomic confusion. Of the two types, only the horse-like species has been found in Canadian fossil beds. These specimens have been attributed to several types including Equus conversidens, Equus lambei,  Equus pacificus, Equus scotti, and Equus verae.  

The validity of the taxonomies is not really the issue to be discussed. What is important is not how many different equids there were, but where they could be found. During the late Pleistocene, the only habitable part of Canada (i.e. the only part not covered in ice) was the stretch of land from northwestern Yukon curving down to southern Alberta and Saskatchewan. It seems there was, at least, a cold weather species (E. Lambei, E. verae) occupying the northern part of this stretch, and a plains adapted species in the south (E. conversidens, E. scotti, E. pacificus).  

If it was decided that equids should be reintroduced to Canada, the question arises of which ones, and where. There are, it seems, three ways to do it. The first, and possibly the most obvious, is to use Przewalski's horses. This Mongolian subspecies of E. ferus (the same species as the domesticated horse E. ferus caballus) is the last of the true wild horses and shares many characteristics with described extinct horse species from both North America and Eurasia. These horses have many advantages for introduction into Canadian ecosystems. First of all, they are not, and never have been domesticated, and thus have kept wild traits both behavioral and physical. This will be useful as they should have better instincts when interacting with humans and other predators. They are also a steppe-adapted horse, which is the predominant ecosystem to which they will be introduced, or at least to similarly levelled and vegetated ecosystems such as plains, pastures, and prairies. The disadvantage is that they may not be able to handle some of the colder climates they would necessarily be introduced to, such as taiga and tundra. Of course this has not been tested, and so it could always be attempted. However, the Przewalski's horse is an endangered species and not only would this make experimental introductions both difficult and expensive, it means it would take a substantial amount of time and resources to create a sufficient founder population. 

The second option, and perhaps a more practical one, is to use the Asian asses; onagers (E. hemionus) and kiangs (E. kiang). These donkey-like wild equids are more readily available and each have several subspecies.  While not as similar physically to the Canadian horse species as the Przewalski's horse, the onagers and kiangs do have several advantages. The first is that, like Przewalski's  horse, they are not domesticated and have experience with predators. Another advantage is their variety, there are four subspecies of onager and three subspecies of kiang. They are found across central Asia in many environments. Kiangs are of particular interest because they can be found in Tibet, a place where, due to high altitudes, very cold temperatures occur. This makes them possibly better candidates for introduction into the colder areas of Canada. So, if this approach is implemented, there could be kiangs of one or more subspecies introduced to areas of northern steppe and mountains, with subspecies of onager implemented in the southern areas of the plains and prairies.  While some subspecies of kiang and onager are endangered some, such as the Mongolian onager or the western kiang, are not and so could more easily be obtained in large numbers to start founder herds. However, as less horse-like animals their ecological role might not line up as well as actual horses. 

The third, and probably the most cost effective approach, is to use domesticated horses of various breeds. This option is the least difficult and the cheapest, but would forfeit the conservation potential and wild nature of the other two options. What is better about this option is that many horse breeds have already been developed that can survive in a multitude of different environments and since breed standards become irrelevant for feral populations, horse breeds can be mixed to capitalize on desirable traits and increase genetic diversity. For example, northern horse herds could be composed of animals from Yakut, Fjord, and Icelandic breed stock, while southern horse herds might be composed of Danube, Mongolian, and Konik horses. There are  many more possible breeds but preference should be given to breeds with some primitive traits such as dun coats, primitive markings, and pony size.  

It is also quite possible to simply combine some of these options. For example, the kiangs and onagers cannot produce fertile offspring with horses, and so could be implemented in the same places as either Przewalski's or domestic horses. This would effectively cover all bases and allow for the fact that there may well have been more than one species of horse in any given area. Another consideration is that Przewalski's horses and domestic horses can produce fertile offspring and so domestic horse herds could be crossbred with material from Przewalski's stallions without compromising the wild Przewalski's herds. In this way horses can be created with the wild traits of the Przewalski's, and the environmental adaptations of domestic horses. If the Przewalski's horses were used, they could be implemented in just the south as well, with other options used in the north. 

Przewalski's Horses https://www.rgo.ru/sites/default/files/styles/headimage/public/loshad_przhevalsko111go_0.jpg?itok=PvrxS2-c

Kiang - http://english.gov.cn/r/Pub/GOV/p1/Content/News/Images/2014/10/27/133745304_14143874991811n.jpg

onager - http://scrolling.blogs.com/.a/6a00d8341bfcce53ef0162fdbbec79970d-pi