ROLE IN ECOSYSTEM

Considering how it changes the environment through its activities, the Ili pika plays a necessary role in its alpine ecosystem. Consisting of plants, vegetation and feces, the haypiles constructed by the species degrade over time and transform into nutrient-rich soil, fertilizer, food and habitat for other animals (Aho et al., 1998). Thus, it is an ecosystem engineer as it modulates the availability of resources to other species, thus modifying, building and maintaining habitats (Jones et al., 1994). Specifically, as an allogenic ecosystem engineer, it changes the environment by transforming living and non-living materials from one physical state to another (International Fund for Animal Welfare, 2022; Jones et al., 1994). The importance of this role is amplified by the fact that the rocky talus areas are barren with limited vegetation and the fertilizer from the haypiles increases nitrogen in the soil, which is scarce at high altitudes (Aho et al., 1998).

KEYSTONE SPECIES

As a species whose presence is key to maintaining biodiversity in an ecosystem and to upholding an ecological community’s structure, the Ili pika is a keystone species for biodiversity in the Tian Shan Mountain alpine meadow ecosystem (Fowler et al., 2013; Smith & Foggin, 1999). The disappearance or extinction of a keystone species can potentially lead to significant ecosystem change or dysfunction on a broader scale (World Wildlife Fund, 2020). As mentioned above, its vital role as an allogenic ecosystem engineer validates it as a keystone species (Aho et al., 1998). Smith and Foggin (1999) suggest that the Ili pika is a keystone species because its nests are the primary habitat for small birds and other organisms, it increases plant species richness through the transformation of degraded haypiles and it serves as the principal prey for nearly every predator species in its distribution area (Aho et al., 1998; Wei et al., 2020).

SPECIES INTERACTION

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. Each organism in a food chain occupies a specific trophic level, or the position of a species in a food chain. At the base of the food chain are producers, or plants that obtain their energy from sunlight. As an herbivore, the Ili pika consumes and obtains its energy from producers; thus, it is considered a primary consumer. Predators of the Ili pika, carnivores that eat primary consumers, are called secondary consumers (Fowler et al., 2013).

PREDATOR–PREY DYNAMICS

In predation and herbivory relationships, an individual of one population kills and consumes individuals of another population (Fowler et al., 2013). The Ili pika is preyed upon by nearly every predator occurring in its distribution area, including foxes, weasels, polecats, falcons and other birds of prey (Ocobock, 2006; Wei et al., 2020). It attempts to avoid predation by remaining under cover of foliage or rocks when active (Ocobock, 2006).

Over time, the population size, or the number of individuals in a population, varies in a cyclical manner (Fowler et al., 2013). According to Fowler et al. (2013) and Ocobock (2006), below is an example of population cycling using the marbled polecat (Vormela peregusma), a predator of the Ili pika:

1. As the Ili pika population increases, more food is available for the marbled polecat.

2. As more food is available for the marbled polecat, the marbled polecat population increases.

3. As the marbled polecat population increases to threshold level, the Ili pika population declines.

4. As the Ili pika population declines, the marbled polecat population declines.

5. When the marbled polecat population is low, the Ili pika population size increases due to low predation pressure.

6. The cycle repeats.

Certain environmental and climatological changes have altered the predator–prey dynamic of the Ili pika. With the decline of grasslands in the Tian Shan Mountains, herdsmen are forced to walk their herds in higher mountain ranges, thus attracting more predators to the pika (Sheridan, 2022). Also, a warming climate in China has increased the presence of vegetation and animal species from lower elevations to the Ili pika habitat, leading to a larger number of attendant predators, such as foxes, to which pika populations had not so far been exposed (Krajick, 2004). Thus, defense mechanisms—specifically behavioral adaptations—against predation and herbivory are necessary for Ili pika survival (Fowler et al., 2013). For instance, the physical appearance of the Ili pika has been adapted to avoid detection by predators (Fowler et al., 2013). Its grey facial hair is highlighted by rusty red spots mimicking in hue the veins of iron oxide that color its rocky habitat (Carpenter, 2018).

Relevant research pertaining to Ili pika predation includes a study by Zhou et al. (2023) investigating predation risk among pikas, in which it was found that pikas instinctually change group sizes when threatened, ultimately decreasing predation risk. According to Smith (2015), though group living among conspecifics is advantageous, the Ili pika is more solitary and not as vocal as other pika species in the Ochotona genus, thus increasing risk of predation.

Wei et al. (2020) utilized various taxidermy predator species models to examine flight initiation distance, hiding time and percentage of vigilance. Findings present that pikas display different behavioral response intensities based on species of predator; for instance, the saker falcon (Falco cherrug) is perceived as the greatest threat by pikas as it elicited the strongest anti-predator behavioral response (Wei et al., 2020). Finally, a study by Holmes (1991) concluded that the risk of predation directly affects pika foraging behavior. In the presence of a predator, he observed pikas concentrating their foraging near talus with limited vegetation as opposed to venturing further away from their rocky habitat where ample vegetation was available (Holmes, 1991).

COMMENSALISM

In symbiotic relationships that are commensal, one species gains from a close prolonged interaction while the other is unaffected and unharmed (Fowler et al., 2013). Within the Ili pika ecosystem, this type of interaction is exhibited in the relationship between the white-winged snowfinch (Montifringilla nivalis) and the pika (Avibase, n.d.; Lai & Smith, 2003). Along with other small bird species, the white-winged snowfinch inhabits pika nests and haypiles (Lai & Smith, 2003; Ocobock, 2006). In this commensal interaction, the Ili pika is unaffected and unharmed by the presence of the white-winged snowfinch (Ocobock, 2006). According to Fowler et al. (2013), however, many possible commensal relationships are challenging to identify as it is difficult to prove that one species does not gain from the presence of the other.

MUTUALISM

In symbiotic relationships between two species that are mutualistic, both species gain from the interaction (Fowler et al., 2013). The relationship between the Siberian chipmunk (Eutamias sibiricus) and the Ili pika is an example of a mutualistic interaction. The Siberian chipmunk is an omnivore that feeds on vegetables, conifer seeds, nuts, shrubs, mushrooms, berries, wheat, oats and insects (Campos, 2022). Both species collect food within close proximity (Smith et al., 2018). When the Siberian chipmunk sees a predator, it vocalizes to alert the pika via a 3–6 syllable repetitive warning call; similarly, the Ili pika, though not as vocal as other pika species, alerts the chipmunk of predators with a high-pitched signal (Campos, 2022; Smith, 2015; Smith et al., 2018).

PARASITISM

A parasitic relationship involves interactions between a parasite, or an organism that feeds off of and uses resources from another organism, and a host, which is the organism being fed upon (Fowler et al., 2013). Unlike in predation, the host is not immediately killed by the parasite; however, it can sicken and die over time (National Geographic Society, 2023b). In this type of relationship, the parasite gains but the host is harmed and weakened from the parasite siphoning resources that the host uses for self-maintenance (Fowler et al., 2013). The Ili pika is a reservoir for various parasites including (a) fleas (Siphonaptera), which can carry the plague (Yersinia pestis); (b) mites (Acari) and ticks (Ixodida), which can transmit diseases and vector-borne infections; and (c) internal parasites such as Coccidia (Meng et al., 2021; Ocobock, 2006). A specific example of a parasite that affects the Ili pika is the warble fly (Oestromyia leporina). According to Fu et al. (2016), larvae of O. leporina parasitize arms, elbows and knee joints of primarily juvenile pikas, causing swelling and anaphylaxis.

ORGANISMS IN THE

ECOSYSTEM OF THE ILI PIKA

Apple Buprestid (Agrilus mali)

ENDANGERED STATUS: Least Concern

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Coleoptera

Family: Buprestidae

Genus: Agrilus

Species: mali

(EPPO Global Database, n.d.)

Native to Northeast Asia, the apple buprestid is a bronze and metallic green beetle that consumes wood in both its larval and adult stages (Zhang et al., 2021). Specifically, the larvae of Agrilus mali inflicts damage to the trunk cortex of the endangered wild apple tree species Malus sieversii (Zhan et al., 2022). It belongs to the phylum Arthropoda—which means “jointed legs”—and thus has jointed appendages and segmented bodies. As an arthropod, it has an exoskeleton made of a nitrogen-containing polysaccharide called chitin (Fowler et al., 2013). A widespread invasive pest, the apple buprestid is distributed among 95% of the Tian Shan Mountain region and is not considered threatened or endangered in the area (Zhang et al., 2021).

Marbled Polecat (Vormela peregusma)

ENDANGERED STATUS: Vulnerable

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Carnivora

Family: Mustelidae

Genus: Vormela

Species: peregusma

(Abramov et al., 2016)

The marbled polecat is a small mustelid with a dark brown head, distinct white and black facial bands, mottling on its back and a fluffy tail (Gorsuch & Larivière, 2005). A mustelid is a carnivorous mammal, meaning it is a meat-eating endothermic vertebrate that possesses hair or fur. It also has mammary glands, which are glands that produce milk for newborns (Fowler et al., 2013). The marbled polecat is a solitary animal with the exception of mating. When threatened, it releases a strong odor from its anal glands, similar to skunks (Amsel, 2023). Considered Vulnerable under the International Union for Conservation of Nature, the species’ population decline is likely attributed to hunting and habitat loss due to cultivation (Abramov et al., 2016; Gorsuch & Larivière, 2005).

Predatory Bush Cricket (Saga pedo)

ENDANGERED STATUS: Vulnerable

Kingdom: Animalia

Phylum: Arthropoda

Class: Insecta

Order: Orthoptera

Family: Tettigoniidae

Genus: Saga

Species: pedo

(Orthopteroid Specialist Group, 1996)

Bright green in color, the predatory bush cricket is the largest insect in the order Orthoptera, typically growing up to 12 centimeters in length (Rogers, 2015). With a specially adapted digestive tract, the species is uniquely carnivorous, cannibalistic and primarily hunts its prey at night (Anselmo, 2022). Saga pedo is has a low population density and is considered Vulnerable under the International Union for Conservation of Nature due to insecticide use and habitat loss (Orthopteroid Specialist Group, 1996).

Saker Falcon (Falco cherrug)

ENDANGERED STATUS: Endangered

Kingdom: Animalia

Phylum: Chordata

Class: Aves

Order: Falconiformes

Family: Falconidae

Genus: Falco

Species: cherrug

(BirdLife International, 2021)

The Ili pika is prey for the fast and maneuverable saker falcon, which has physically adapted to hunting close to the ground (Bird Life International, 2021). Prior to growing into a full plumage of dark grey flight feathers, hatchlings are covered in white fluffy down feathers, which are feathers specialized for insulation (Animal Spot, 2023; Canadian Raptor Conservancy, n.d.; Fowler et al., 2013). Under the International Union for Conservation of Nature, Falco cherrug is considered Endangered with a declining trend, mostly due to capture and trapping for the international falconry trade (BirdLife International, 2021).

Siberian Chipmunk (Eutamias sibiricus)

ENDANGERED STATUS: Least Concern

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Rodentia

Family: Sciuridae

Genus: Eutamias

Species: sibiricus

(Tsytsulina et al., 2016)

The Siberian chipmunk is recognizable with its brightly colored coat and dark stripes down its back (Campos, 2022). With large cheek pouches for food storage, it possesses heterodont teeth, meaning it has different types and shapes of teeth for feeding on a variety of foods (Fowler et al., 2013). Specifically, front incisors are used for gnawing and the function of cheek teeth is to chew and grind (Legendre, 2003). While the Siberian chipmunk lives mainly on the ground, it is an excellent climber with needle-pointed claws (Campos, 2022). According to the International Union for Conservation of Nature, Eutamias sibiricus is considered stable due to its wide distribution and large population size (Tsytsulina et al., 2016).

Siberian Ibex (Capra sibirica)

ENDANGERED STATUS: Near Threatened

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Cetartiodactyla

Family: Bovidae

Genus: Capra

Species: sibirica

(Reading et al., 2020)

Measuring 70 inches long and weighing in at almost 300 pounds, the Siberian ibex is the largest and heaviest species in the wild goat genus Capra (Fedosenko & Blank, 2001). According to Han et al. (2021), the species climbs and moves through terrain more quickly than predators, using rocks and cliffs as a refuge. With circular rings representing annual growth, the recurved horns of the Siberian ibex can grow up to 60 inches tall (Fedosenko & Blank, 2001). Primarily due to harvesting by subsistence hunters for meat and trophy hunters for skulls and horns, Capra sibirica is considered Near Threatened with a decreasing trend under the International Union for Conservation of Nature (Reading et al., 2020).

Tianshan Birch (Betula tianschanica)

ENDANGERED STATUS: Endangered

Kingdom: Plantae

Phylum: Tracheophyta

Class: Magnoliopsida

Order: Fagales

Family: Betulaceae

Genus: Betula

Species: tianschanica

(Roy et al., 2018; UN Environment World Conservation Monitoring Centre, 2013)

Standing approximately 10 meters tall, the Tianshan birch is a relatively small tree with a pinkish peeling bark and firm deciduous leaves. Similar to that of the Ili pika, its habitat consists of rocky slopes as well as temperate forests and shady valleys (International Dendrology Society, n.d.). Betula tianschanica is a rare species occurring in isolated populations. Due to its limited distribution and rapid decline, it is considered Endangered and is especially susceptible to threats including avalanches, livestock grazing, firewood collection and tourism (Roy et al., 2018; UN Environment World Conservation Monitoring Centre, 2013).

Wild Apple (Malus sieversii)

ENDANGERED STATUS: Vulnerable

Kingdom: Plantae

Phylum: Tracheophyta

Class: Magnoliopsida

Order: Rosales

Family: Rosaceae

Genus: Malus

Species: sieversii

(Centre for Agriculture and Bioscience International, 2019)

Found on the mountain summits, slopes and valleys of the Tian Shan Mountains, Malus sieversii is a wild apple tree native to the Xinjiang Uygur Autonomous Region in China (Global Trees Campaign, 2020; Yang et al., 2016). Approximately 10 meters in height and similar in appearance to the common apple (Malus pumila), it is a deciduous, fruit-bearing tree with the ability to grow in a variety of habitats and climates (Yang et al., 2016). Malus sieversii is considered Vulnerable due to its limited range and habitat loss from agricultural development (Global Trees Campaign, 2020). Presently, the largest threat to the species is the larvae of the invasive apple buprestid (Agrilus mali) feeding on the tree’s inner bark (Centre for Agriculture and Bioscience International, 2019; Zhan et al., 2022).

Yarkand Hare (Lepus yarkandensis)

ENDANGERED STATUS: Near Threatened

Kingdom: Animalia

Phylum: Chordata

Class: Mammalia

Order: Lagomorpha

Family: Leporidae

Genus: Lepus

Species: yarkandensis

(Smith & Johnston, 2016)

Native to the Xinjiang Uygur Autonomous Region in China, Lepus yarkandensis is a small hare weighing approximately four pounds with long ears measuring four inches in length (Hoffman & Smith, 2005). Active at dawn and dusk, the Yarkand hare is a crepuscular species that forages on grass and crops during the early morning and late evening (Chapman & Flux, 1990). The species is specifically distributed in the steppes of the Tarim Basin (Hoffman & Smith, 2005). Hunted for game and poached for its pelt, the Yarkand hare is considered Near Threatened under the International Union for Conservation of Nature with a decreasing trend (Smith & Johnston, 2016).