Course:CONS200/2021/Climate Change and the American Pika

Introduction to the American Pika

American Pika (Ochotona princeps)

Known to be one of North America's toughest species, the small, furry American Pika (Ochotona princeps) could be found anywhere on the continent just 12,000 years ago. In recent times however, the species range has shifted upwards in elevation in response to a warming climate. The species currently inhabits the western U.S. and southern Canada, they have been pushed to the margins, mainly above mountain tree lines. With primarily brown and grey coloration, they are able to blend in well on the talus mountain sites that they inhabit. Due to their thick fur coat, they are prone to overheating come the summer time. At 25°C, the American Pika have a difficult time surviving and so naturally, climate change is becoming a relevant issue for the species.

The decline in the population of the American Pika is concerning, however there is a glimmer of hope as it seems certain subpopulations have found alternate survival methods. By looking at the species different subpopulations, it becomes clear that the entire species is not suffering but rather specific populations are, such as the those that live in the Great Basin (primarily in Nevada and sections of surrounding states). Meanwhile other American Pika populations are continuing to thrive in bio-geoclimatic regions that were once thought to be out of their physiological range, suggesting that the species is may be able to adapt in the face of climate change. There are many possibilities as to how they are doing this, but a common consensus is that it has to do with their impressive behavioural flexibility.

Physical Characteristics

The American pika is a small mammal that resembles the rabbit, a close relative of the pika. They have a mean body mass of 121g-176g, have short limbs, short, round ears, and they appear tailless because the have a buried tail. The pika molts twice annually: in the summer they display grey-brown pelage, and in the autumn and winter they display longer, grey pelage.

Habitat/Niche

American Pika (Ochotona princeps) in rocky habitat.

The American pika is an alpine specialist whose habitat include rocky hills, lava beds, and talus slopes in mountain ranges such as the Sierra Nevada, Rocky Mountains, and the Cascade Ranges. These locations provide a safe refuge from their predators such as coyotes (Canas latrans), longtail weasels (Mustela frenata), shorttail weasels (M. erminea), and pine martens (Martes Americana). These high elevation rocky locations also provide cooler microclimates which are a buffer from temperature fluctuations. Bordering their den sites are often alpine meadows where the pika can forage throughout the day. Ideal habitat has alpine meadows close by so that the pika can successfully forage during their limited time for surface activity. The pikas upper limit of temperature tolerance is approximately 20°C, above which they will have an high chance of mortality if they are unable to return their cooler rocky habitat. Pikas are herbivorous, primarily feeding on short alpine grasses during the summer months and cushion plats and lichens in the winter months. They supplement their winter diet with food they gathered throughout the summer and stored in haypiles.

Life History Traits

Pika displaying round ears and "tailless" body.

Life history traits are the stages an organism goes through in its lifetime from birth, growth, reproduction, and death. These traits are heritable, have variation within the population, and the differences in individual organisms survivorship and fitness are linked to these traits. In this way, life history traits can evolve through natural selection to allow populations to adapt to their changing environments.

The maximum lifespan of the American pika is seven years. Age specific mortality rates increase from birth to year one and again at age five to seven (end of lifespan). The pika is one year at the age of first reproduction and produces approximately two litters per year, with an average litter size of three. Pikas are poor dispersers because they are philopatric, meaning they do not travel far from their birthplace. Dispersal is generally limited to the juveniles who may only dispers as far as 2-3km on occasion to find unoccupied habitat in order to decrease intraspecific competition.  

The pika has behavioural adaptions that make them well suited to their cool alpine environments. Behavioural thermoregulation is used to buffer their narrow range of thermal tolerance. In order to thermoregulate, the diurnal pika’s minimize their surface activity such as foraging and, therefore, the time they are exposed to surface temperatures. They do this by venturing out into the warmer surface temperatures infrequently and only for short periods of time. They do not travel far from the cooler microclimate found in their talus habitat.

The pikas physiological adaptations to the alpine environment comes from their thick pelage with they grow each winter and shed in the summer for lighter pelage.

Effects of Climate Change on the Pika

American pika (Ochotona princeps) with a mouthful of flowers.

Background

In order to understand how climate change has impacted the American Pika, it is important to understand their evolutionary history. Scientists have discovered that heat makes the small mammal far less mobile, while cooler temperatures allow them to become more active. This allows them the potential to disperse and colonize nearby surrounding areas. The pika arrived in North America 5 million years ago from Asia, and took advantage of the era's cooler climate, quickly expanding their range across the large land mass. This movement was reduced however when the temperature began to rise, resulting in the American Pika being forced upwards in elevation to seek cooler temperatures. Over the last 5 million years, paleontological efforts uncovered that the species habitat have fluctuated up and down in elevation along with periods of cooling and warming. This would indicate that they are in fact impacted by climate change.

This concern that the American Pika will be impacted by climate change is further supported by their physiology. With a resting body temperature of 40.1°C, the small mammals are extremely sensitive to warm temperatures. This relatively high body temperature is in large part due to their thick pelage that allows them to survive harsh winters, however as climate change becomes more prominent, these harsh winters become less frequent and extreme, reducing the need for such pelage. Adding to the problem is the fact that they do not hibernate and that they keep a high metabolism. In order to keep up their nutritional intake (consisting of mainly grasses and weeds), maximizing their foraging time is critical, especially in late summer when they stock pile for winter. However, as surface temperatures increased their foraging time decreased. This reduced time to forage for food would potentially lead to a decrease in fitness, and yet, recent research has come out showing that much of the lowerland American Pika populations are still thriving, which begs the question, how are they doing this?

Adapting Behaviours

In the last few years, recent studies have shown that the small mammals have a lot of behavioural flexibility. This means that they are able to alter their behaviour in response to their environment. To adapt to a warming climate, the American Pika had to change how they forage. Rising temperatures has forced the previously diurnal creature to search for their food at night while temperatures are cooler. While the sun is out, the Pika’s can be found deep in their dens. Additionally, their diet has changed as well as their foraging tactics. Once believed to have a more specialized diet, the American Pika has been observed to survive on a wider variety of food sources including shrubs, graminoids, and even at times, mosses (primarily only in the Columbia River Gorge population).

Potential Weakness

Although this new research is promising for the American Pika when it comes to surviving climate change, one weakness of the small mammals is their poor dispersal ability. Because the upper limits of their dispersal is 300 metres, they are often left stranded when their area comes under pressure. As previously discussed, the American Pika is able to tolerate far less surface activity in warmer weather, therefore, as the temperature rises, the species movement will be reduced. A study proved this when they marked 139 adults all in the same habitat population and only 2 dispersed to a new patch after a year. This becomes an issue in this anthropogenic age, as humans have taken over much the land the Pika's once inhabited typically in talus forefields. Cattle ranching specifically has put much of their habitat in danger, due to the intense grazing that takes place, which destroys biomass that the Pika's need for their daily forage. Because of this, specific American Pika populations can be quickly extirpated.

An additional potential problem the pika faces relates to the low snowfall rates anticipated under the warming climate. In the winter, the snow acts as an insulating layer, protecting the pika rom the cold outside temperatures. In the absence of this protective layer, the pika would have to expend more energy thermoregulating and use more metabolic reserves, potentially decreasing the individuals fitness.

Low colonization rates can have negative effects on population growth rates for the American Pika but luckily, their behavioural flexibility might save them from extinction. Although their preferred habitat is quickly shrinking, some populations have found ways to adapt.

Conservation Efforts

American Pika (Ochotona princeps) in Rocky mountains (Colorado), Poudre Canyon National Park.

The pikas high elevation habitat is a concern because as temperatures continue to increase, the fear is that many populations will not have higher elevations to retreat to. If the mountain a population inhabits is not high enough, many pika populations risk the temperatures of their habitat exceeding the upper limits of tolerance. The data shows that only the highest peaks of Sierra Nevada are capable of hosting the pikas if temperatures continue to increase. This concern has been the centre of the conversation around the American Pika because if temperatures rise there is nowhere for them to migrate to without human intervention and assisted migration. Due to this, many scientists have identified them as an indicator species for climate change (CITE). Various organizations like The Center for Biological Diversity have put in efforts to place the American Pika under the protection of endangered species act. After an assessment in 2016, the IUCN Red List categorized the American Pika under "Least Concern" with global populations decreasing. In addition, the pika is not listed under the Canadian Species at Risk Act (SARA), the United States Endangered Species Act, or under the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Even so, many researchers are closely monitoring the species to see how it will adjust to the rapidly changing climate. Potential solutions for local populations at risk of extirpation include assisted migration to higher elevation mountains, particularly in the Great Basin where quite a high percentage of their potential habitat remains unoccupied. Big picture actions include changing legislation for less global warming stressors, increasing awareness, and identifying new protection areas. However, the severity of the problems have been questioned as it has been examined that the Pika’s has been able to survive the higher temperatures than previously believed by engaging in more nocturnal behaviour while sheltering from the heat of the day in their habitat. Although it is true that climate change is affecting the lives of American Pikas, there seems to be plenty of literature that is questioning the immediacy of possible extinction of American Pika’s due to climate change that has been portrayed.

Conclusion

The American Pika are a resilient species in the face of climate change. Facing the threats of global climate change, research has strongly indicated that the American Pika has the ability to mitigate its stressors. Experts such as Andrew T. Smith suggest that much of the concern for the plight of the pika has come from media sensationalism rather than scientific fact. While some populations have faced decline, many are thriving and the plight of one population should not become a generalization for the entire species. However, as climate change and anthropogenic disturbances cause habitat loss, degradation, and rising temperatures, the American Pika should continue to be studied closely. Certain populations are doing better than others and there are limitations to the resilience of any species in this unprecedented time of climate change. Therefore, areas of concern for these species should continue to be monitored for the day that human intervention may be needed.