- Climate change and increasing human impact in the Himalayas are a threat to the survival of cold-adapted Himalayan pikas which play a crucial role in their ecosystem.
- A new study examines the winter survival strategies, food caching behaviour, and haypile contents of two pika species in Ladakh.
- The research reveals that Ladakh and Nubra pikas, each with distinct “personalities,” wait for specific weather cues before food caching, at the same time, exhibit significant differences in the size and structure of their haypiles.
There is certainly more to pikas than meets the eye. To the untrained observer, they might appear as just another cute, fluffy creature scampering around Alpine terrains. However, these small mammals in the high mountains of the Himalayas play crucial roles in those ecosystems, such as supporting a diverse array of plant life.
Associate professor Nandini Rajamani from the Indian Institute of Science Education and Research (IISER) Tirupati, who has studied these species extensively, likens pikas to “farmers.” She notes that a wide diversity of flora is often observed around pika colonies, likely due to their constant activities, such as digging and altering soil conditions, which promote the growth of various plants. Additionally, pikas, along with other small mammals like marmots and voles, serve as important prey for a range of predators, including raptors, small wild cats, and canids.
The climate connection
Climate change and increasing human activity are threatening the survival of many cold-adapted species, including pikas. Rajamani notes that glaciologists have observed rising glacier melt in the Himalayas, which has a cascading effect on local micro-ecosystems, many of which remain unassessed.
For cold-adapted species such as pikas, survival depends not only on weather patterns but also on the overall environment, which must remain cold through features like glaciers and permafrost. “Nobody knows what will happen to animal populations dependent on cold environments; they might disappear if they cannot adapt to new conditions,” she says. She adds that some of her previous work indicates that pikas have been highly threatened historically and that their populations are shrinking. “They don’t have many places to go if their habitat continues to diminish.”
Most Himalayan pikas rarely encounter humans, but when they do, they often become dependent on them for easy meals, says Nishma Dahal, DST-INSPIRE faculty and Assistant Professor at the Academy of Scientific and Innovative Research (AcSIR), CSIR-Institute of Himalayan Bioresource Technology. “Talus-dwelling pikas, such as Ochotona roylei, sometimes use human-made walls for shelter. In contrast, species like O. nubrica tend to avoid humans. Therefore, the behavioural strategies that will help these species survive as humans encroach on their territory appear to be species-specific,” she explains.
Pikas belong to the family of Ochotonidae, in the order Lagomorpha, which also includes rabbits and hares in the Leporidae family. Out of the 37 pika species identified, seven occur in India. However, there is limited knowledge about them, as much of the existing literature on pikas is based on studies conducted in the West.
Therefore, a new study by a research team from IISER Tirupati is particularly significant as it investigates a unique seasonal behaviour of pikas that is vital to their survival. The study focuses on the haying and food caching behaviours in two pika species — Ochotona nubrica (Nubra pika) and Ochotona ladacensis (Ladakh pika) — from the cold desert of the Changthang biotic province in Ladakh.
Storing for a wintry day
One might be tempted to label pikas as “hoarders.” They accumulate and store vegetation, their primary food source, sometimes caching up to 23 kg, depending on the species and the sizes of their colonies. However, this apparent “gluttony” is a survival strategy for these cold-adapted animals, as minimalism in high altitudes could be suicidal. Through food collection and storage behaviours of haying and caching, pikas prepare for harsh winters when food resources become scarce and mortality rates among many animal species increase.
The lead author of the new paper Harsha Kumar noticed both Ladakh and Nubra pikas caching vegetation in Ladakh, which sparked his interest in exploring this behaviour further. The contrast between their “personalities” — Ladakh pikas occupy more open habitats such as Alpine steppes and are larger in size and bolder than the shy Nubra pikas that colonise places with more vegetation — added to the intrigue.
Ladakh pikas also have larger social structures, with colonies typically comprising 20 to 50 individuals. In contrast, Nubra pikas form smaller groups, usually consisting of eight to ten individuals. However, colony sizes for both species can vary significantly. “We have even observed a Ladakh pika colony with just four individuals,” notes Rajamani who co-authored the new study.
Behavioural adaptations
Pikas do not hibernate during harsh winters; instead, they make numerous behavioural adaptations to survive. Of the 37 pika species, 21 are known to construct haypiles regularly, but there is limited information on the remaining species.
Dahal notes that hay caching is relatively uncommon among Himalayan pikas. She has observed certain species, such as O. sikimaria and O. curzoniae — which are sister species to O. nubrica — occasionally feeding on yak dung for energy, a behaviour also documented in other studies. “Similarly, minute actions, like their sitting posture, help pikas dissipate heat,” she says, adding that these observations suggest that behaviour plays a crucial role in their survival in harsh environments. This, in turn, highlights the importance of behavioural studies in understanding pikas better. However, studying Himalayan pikas presents challenges due to the seasonality of their environment, which results in a very short observational window, she points out.
Researchers investigated the size, composition, and distribution of haypiles, as well as variations in hoarding behaviour between the two pika species. Although haypile sizes and contents varied across colonies and species, the evidence suggests that food-caching behaviour serves as a flexible bet-hedging strategy for potential winter survival, according to Kumar.
Bet-hedging is an evolutionary adaptation that helps organisms reproduce and persist in unpredictable environments. In this context, pikas employ a bet-hedging strategy by waiting for environmental cues indicating a severe winter before committing to haypiles. This approach maximises their fitness, as the time and energy spent constructing haypiles could otherwise compromise their reproductive success during the summer, the paper notes.
Prepping for winter
A considerable variation in haying behaviour was observed within and across the colonies of the pika species studied. The authors suggest that this variation could be related to differences in snowfall patterns in Ladakh during winter, which affect food availability for the species.
In terms of hay caching patterns, the study found that Ladakh pikas, with their larger sizes, social groups, and open habitats, engaged in “larder hoarding” — they built large hay piles and guarded them aggressively against theft from other pikas. In contrast, Nubra pikas, which live in smaller social groups at lower densities in more enclosed landscapes, practised “scatter hoarding.” They constructed smaller haypiles and dispersed them throughout their colonies.
The haypiles of Ladakh pikas were found to be more clumped in distribution and contained a greater variety of plant species compared to those of Nubra pikas. Different pika species are known to exhibit variation in the plant composition of their haypiles, and this was true for the species studied. For example, haypiles of O. dauurica contain up to 10 different plant species, while O. turuchanensis can include as many as 26 plant species. In contrast, O. princeps selectively caches up to 12 different plant species, with up to three species forming the bulk of each haypile, according to the paper.
Kumar explains that Ladakh pikas were observed to include plants with high protein and carbohydrate content in their haypiles, such as winterfat (Krascheninnikovia ceratoides), a plant that is also foraged by local herders. In contrast, some plants that are abundant in their habitats were ignored by Ladakh pikas. Interestingly, Kumar notes, “Nubra pikas included locoweeds in their haypiles, which is unusual since these toxic plants are often avoided by herbivores.”
While Kumar acknowledges that this study is just the beginning of a series of planned investigations into these species, he points out that it has already provided answers to many of the initial questions they posed. However, several crucial questions remain unanswered, such as why Nubra pikas include loco weeds in their haypiles and why they practice scatter hoarding. Kumar hopes that follow-up studies will address these unresolved issues.
Read more: New species of rabbit-like pika discovered in India
Banner image: Ladakh pika. In a unique study, the hay caching behaviour of two Himalayan pikas were studied to find that it is a selective behaviour depending on weather cues. Image by Dhanesh P.
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