The New Mexico Rare Arthropod Resource

The Capulin Mountain Arctic is found in the harsh windswept fescue mountain grasslands of mesa tops and isolated summits within the Raton Mesa complex, and formerly including Capulin Volcano (Cary et al. 2004, NPS 2012). In Capulin the taxon was found at the crater rim on the highest elevation points possible (Cary et al. 2004). Currently the host plant for this taxa is not known however, the parent species uses Bunch Grasses (Fescue) and that is likely also the case for O.a. capulinensis as the butterfly seems to be associated with habitats which contain large amounts of fescue bunch grasses (Scott 1986, Parmenter et al. 2000, Cary et al. 2004). At present the necessary Fescue may still present at Capulin Mountain however, only as isolated individuals which are collectively insufficient to support a population of this taxa (S. Cary Pers. Comm 2024). This butterfly seems to have one short flight from mid-May to early June (Brown 1970, Cary et al. 2004). This subspecies has been described as rarely flying unless it is kicked out of grass clumps which has made surveying for them challenging (Brown 1970, Cary et al. 2004). When this butterfly does fly its flight is described as erratic, rapid, and low to the ground, usually less than a foot above the grass (Brown 1970 Cary et al. 2004). Only males have been observed flying thus far while female butterflies have been seen crawling on the group among grass clumps or crawling in and out of crevices in the volcanic cinders (Brown 1970, Cary et al. 2004, NPS 2014). Ultimately very little is known about this taxon’s life history and additional knowledge is needed to properly conserve the Capulin Mountain Arctic.

According to out current knowledge, this butterfly is endemic to the Raton Mesa Complex, a very small area in northern New Mexico and southern Colorado. This subspecies was first discovered in 1969, at Capulin Volcano National Monument (Cary et al. 2004, NPS 2012, Cary and Toliver 2023). However, the subspecies is now thought to be extirpated at Capulin Volcano National Monument and as such the Raton Mesa Complex is the only known location for this subspecies (Cary et al. 2004, Cary and Toliver 2023). However, Capulin Mountain and Raton Mesa are both part of a series of isolated summits and broad mesas that make up the larger Raton Mesa Volcanic Field, a geologic feature which extends 100 miles from Raton, New Mexico east to Black Mesa Oklahoma, and 40 miles from Trinidad, Colorado to Gladstone, New Mexico. The enitre geologic feature encompasses nearly 4,000 square mile, across which there are dozens of volcanic summits and broad mesas which have not been searched for the Capulin Mountain Arctic (Muehlberger et al. 2005, S. Cary pers. comm. 2024). As a result, additional surveys may reveal that this taxons range is larger than currently thought.

There is one known prior conservation of this taxa which was done by NatureServe in 1998. In this assessment the Capulin Mountain Arctic was found to be globally imperiled with extinction (NatureServe 2023). However, this assessment is very out of date now, being run in 1998 and this was before the subspecies extirpated at Capulin Volcano National Monument. This assessment also counted intermountain Oeneis alberta oslari as O.a. capulinensis (C. Nunes Pers. Comm 2024). 

Cary et al. 2004 recommended regular systematic surveys to try to determine the full population number and extent of this subspecies and to try to learn its life history. We agree with this and see it as the most pressing conservation matter for this taxa. Determining if this taxa is in on any more mesas and the size of its population will be crucial to ensure the health of the subspecies. Determination of life history information is also needed to properly conserve this taxa currently Bartlett Mesa is the only place its been seen in the last twenty years if this is truly the last locality for this butterfly then it is threatened with imminent extinction and immediate efforts are needed to try to conserve and restore habitat for this taxa. An important aspect of this habitat restoration and reintroduction will be determining the host plant of this butterfly. Currently Capulin Mountain does not have enough Fescue to sustain a population of this butterfly but with some restoration the Capulin Mountain Arctic may once again grace its namesake.

 However, populations of butterflies on isolated peaks in New Mexico face a bleak future with climate change including peaks like Capulin Mountain. The high mesa tops such as Bartlett mesa though are quite extensive and there is still hope that if conservation efforts are focused on these areas that enough habitat could be maintained or restored on these mesas to save the Capulin Mountain Arctic (S. Cary Pers. Comm 2024). As a result, this is where we recommend conservation efforts on this butterfly be targeted presently is within determination of this butterflies range, population size, and with the maintenance and restoration of these high mesa tops.  

However, more direct conservation measures may also be needed to ensure this subspecies’ continued survival. This includes habitat management especially as it relates to fire and invasive species as either fire or invasive species could easily extirpate the remaining known population. If the situation continues to get more dire and we risk losing the only remaining known population in Raton then captive rearing, assisted migration, or hybridization may be necessary. Additionally, permit free collection should no longer be allowed in this taxas range as with the current known population being on just a single mesa one large collection event similar to the one years ago where an individual took 200 specimens could result in the extinction of this butterfly (S. Cary Pers. Comm 2024).  

The Capulin Mountain Arctic butterfly faces many potential threats in its range. First off because of the population’s small size, small natural or human impacts could threaten the existence of this subspecies (Cary et al. 2004). These could include loss of larval host plants due to development or replacement by invasive species (Cary et al. 2004). In many other places the parent species has been driven out of habitats due to overgrazing of cattle and non-native grasses (Cary et al. 2004, NatureServe 2023). This subspecies could also be highly affected by fire either by it or the lack of it. With such small population numbers in such small areas one fire controlled or wild could wipe out a large percentage of what's left of this subspecies and potentially cause its extinction (Cary et al. 2004). However, at the same time with no fire these grasslands may grow senescent or be succeeded which will also drive the taxa towards potential extinction (Cary et al. 2004). Because the current known population is so small and it's so restricted drought, and severe weather pose large challenges to the taxa as well including hailstorms and late snows which if during the flight period could kill off a large number of individuals (Cary et al. 2004). On top of all of this the subspecies is univoltine and being univoltine highly increases a butterflies chances of extinction making them less adaptable and more prone to phenological mismatch (Forister et al. 2023).  

Additionally, the population appears to have poor genetic health and be quite inbred based on the amount of recessive phenotypes observable in the population and its long-term isolation (Brown 1970, Cary et al. 2004). In a metapopulation like this it is not uncommon for events like weather or climate to extirpate small colonies, however, eventually they will be recolonized from another population (Cary et al. 2004). But with this taxon it does not seem like recolonization will be an option at many sites. This subspecies is a relict from a much colder time and climate warming has now driven the taxa as far up these mesas and volcanoes as it can get to replicate the colder temperatures it needs. On top of this, at some of the sites it is now gone from such as Capulin Volcano it would have to travel some distance across low elevations to get there making recolonization unlikely (Cary et al. 2004). As climate change continues and temperatures get warmer this subspecies is expected to be pushed to higher and higher altitudes however, at this point it can’t increase in elevation anymore as it already exists towards the tops of the grassy Raton Mesas (Cary et al. 2004). It also has limited dispersal capability and so seems to be facing imminent extinction in New Mexico with climate change (Cary et al. 2004). Currently the climate projections for Capulin Volcano National Monument and the Raton Mesa complex show the landscaping getting much warmer and drier, a future that undoubtedly will be harsh on the Capulin Mountain Arctic (NPS 2012).  

Since 1969 when the subspecies was first identified it has only been found six more times at Capulin Volcano National Monument with the last sighting there occurring in 1996 (NPS 2012). In 2003 and 2004 the National Park Service underwent formal surveys to try to determine the abundance and population of the subspecies and although none were found at the monument either year the taxon was found at other nearby mesas around Raton although in very low numbers (Cary et al. 2004, NPS 2012). Additionally, this subspecies is phenotypically far more variable than any other studied population and this degree of variation seems to suggest a very small and isolated population where many recessive traits have begun to appear phenotypically (Brown 1970, Cary et al. 2004).  

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