Shared Pastures: Diet Overlap between Livestock and Wild Herbivores in the Greater Himalaya
By
Lisa Koetke
Trekking through the Himalayas makes me feel as though I am on top of the world. I become enraptured by the flow of the brilliantly blue river through lush alpine meadows, the high peaks towering above me, and the vast glaciers spread out ahead. The serenity of the mountains allows me to leave the rest of the world behind, and forget the hustle and bustle of the city. That is until I come around a corner and almost collide with a herd of a few hundred goats. Lead by a pair of shepherds, the goats seem wary of me, but I can hear them continuing to chew on the last bite they took. Transhumance pastoralism is a common livelihood among communities in the Himalaya. Shepherds bring their livestock up into the mountains when the snow melts in the spring, and move them from meadow to meadow to benefit from lush vegetation. Alpine meadows of the Himalayas have supported this traditional way of life of nomadic shepherds for centuries.
These grazing lands are still used today, and the number of livestock has increased in recent years. While some livestock grazing in alpine meadows can be sustainable, many rangelands in the Trans-Himalaya are overstocked to the point of reducing livestock outputs. Overstocking these rangelands can also impact wildlife populations. It can affect what habitats and elevational range they use, as well as what forage they consume. Overgrazing by livestock can reduce forage quantity and quality, which can limit livestock and wild herbivore populations alike. Determining whether rangeland is overstocked is crucial for protecting the habitat which supports both shepherds and wild herbivores. This can be done by analyzing the habitat use and diet selection by wild herbivores since they modify these behaviors in response to changes in the habitat.
In Uttarakhand State, habitat use by wild herbivores has been shown to shift in response to livestock grazing. In the Bhagirathi river catchment, as in many other areas of the Greater Himalaya, livestock and wild herbivores often prefer to graze in the same meadows, but not at the same time. During spring, wild herbivores occupy the meadows as the snow melts, then livestock arrives, and the wild herbivores move out of the high-quality grazing areas. In autumn, livestock begins to leave the meadows, but wild herbivores only graze in the high-quality meadows once the livestock travels to lower elevations for winter. The second group of animals to occupy the grazing meadows can experience competitive pressure through reduced forage quantity and quality. However, few studies have compared the diets of livestock and wild herbivores in the Greater Himalaya.
In Uttarakhand State, habitat use by wild herbivores has been shown to shift in response to livestock grazing. In the Bhagirathi river catchment, as in many other areas of the Greater Himalaya, livestock and wild herbivores often prefer to graze in the same meadows, but not at the same time. During spring, wild herbivores occupy the meadows as the snow melts, then livestock arrives, and the wild herbivores move out of the high-quality grazing areas. In autumn, livestock begins to leave the meadows, but wild herbivores only graze in the high-quality meadows once the livestock travels to lower elevations for winter. The second group of animals to occupy the grazing meadows can experience competitive pressure through reduced forage quantity and quality. However, few studies have compared the diets of livestock and wild herbivores in the Greater Himalaya.
The Bhagirathi River Catchment
We assessed the diet of wild herbivores and livestock in the Bhagirathi river catchment, Uttarakhand. The study area is in the mountainous region east of Yamunotri and west of Gangotri. It ranged from 3500 m to 4100 m in elevation and included alpine meadows and birch-fir forests.
The Herbivores of Interest
Blue sheep live in groups and graze in open alpine pastures at high elevations. They use cliffs and steep, rocky slopes to escape from predators. They are the main prey of snow leopards, which are vulnerable to becoming endangered. Blue sheep are adapted for a diet dominated by grasses and sedges. However, grasses and sedges can make up as little as half of their diet in winter and highly grazed areas.
Musk deer is a small deer that live mostly solitarily. The males have long canine teeth rather than antlers. Their distribution in the Himalaya is patchy, and the species is endangered due to poaching and habitat destruction, and degradation. Musk deer primarily eat shrubs and herbs, but there are few detailed studies of their diet.
Domestic goats and sheep are the primary livestock in the study area. They mostly eat grasses, but can also incorporate shrubs and herbs. The number of shepherds and livestock are not monitored.
Musk deer is a small deer that live mostly solitarily. The males have long canine teeth rather than antlers. Their distribution in the Himalaya is patchy, and the species is endangered due to poaching and habitat destruction, and degradation. Musk deer primarily eat shrubs and herbs, but there are few detailed studies of their diet.
Domestic goats and sheep are the primary livestock in the study area. They mostly eat grasses, but can also incorporate shrubs and herbs. The number of shepherds and livestock are not monitored.
What are They Eating?
To assess the diets of the three herbivores, we collected samples of their fecal pellets in the spring and fall. Using a microscope, we identified the plant cells remaining in the pellets to obtain information about what the herbivores ate. We calculated diet preference to compare how intensely the herbivores used a resource relative to its availability. We calculated diet breadth to determine how specialized or general their diet is. Finally, we calculated diet overlap to assess how similar the diets of the three herbivores were.
In the spring, livestock ate mostly grasses with some trees, shrubs, and herbs. Blue sheep ate almost entirely grasses, and musk deer ate mostly trees with some herbs and shrubs. Livestock avoided herbs, blue sheep strongly preferred grasses, and musk deer preferred trees. The breadth of the resources consumed was largest for livestock and blue sheep, and narrower for musk deer. The diet of livestock overlapped with both wild herbivores, but more with musk deer than blue sheep. In the fall, livestock ate almost entirely grasses, whereas blue sheep ate more shrubs than grasses. Musk deer ate herbs, shrubs, and trees. Livestock and blue sheep both strongly preferred grasses compared to their availability, whereas musk deer preferred trees and herbs. The breadth of the diet of blue sheep was the largest. The diet of blue sheep overlapped significantly with both livestock and musk deer.
In the spring, livestock ate mostly grasses with some trees, shrubs, and herbs. Blue sheep ate almost entirely grasses, and musk deer ate mostly trees with some herbs and shrubs. Livestock avoided herbs, blue sheep strongly preferred grasses, and musk deer preferred trees. The breadth of the resources consumed was largest for livestock and blue sheep, and narrower for musk deer. The diet of livestock overlapped with both wild herbivores, but more with musk deer than blue sheep. In the fall, livestock ate almost entirely grasses, whereas blue sheep ate more shrubs than grasses. Musk deer ate herbs, shrubs, and trees. Livestock and blue sheep both strongly preferred grasses compared to their availability, whereas musk deer preferred trees and herbs. The breadth of the diet of blue sheep was the largest. The diet of blue sheep overlapped significantly with both livestock and musk deer.
Are Alpine Meadows Overstocked?
Blue sheep are expected to eat mostly grass, which was supported by their strong preference for grasses in both spring and fall. In the spring, when blue sheep occupied the grazing meadows before the livestock, grasses made up the majority of their diet. However, in the fall, when blue sheep occupied the grazing meadows after the livestock, they consumed more shrubs and herbs than grasses. Furthermore, the diet breadth of blue sheep was wider than that of livestock in the fall, so they may be incorporating additional forage options into their diet. This can occur in response to limited preferred resources. The large number of livestock in the study area and the increased reliance of blue sheep on browse in the fall suggest that intense livestock grazing may be reducing the availability of grasses preferred by blue sheep. Blue sheep tend to consume more shrubs and herbs in the winter, but the seasonal changes in the blue sheep diet are amplified and begin earlier in the year in our study area. This may be related to the reduced availability of grasses; the amount of forage available in the high-quality grazing meadows was noticeably depleted after the livestock left in the fall.
As expected, musk deer consumed shrubs and herbs. However, the high proportion of trees (mostly pine) consumed by musk deer in the spring was previously unknown. Few studies have documented the diet of his endangered species, so this new information may be useful in protecting musk deer habitat. The diet of musk deer overlapped with that of livestock in the spring, but this likely does not strongly impact the musk deer population, because livestock arrived in the study area after the musk deer.
Our research indicates the potential for wild herbivores, especially blue sheep, to be impacted by livestock grazing in the Bhagirathi river catchment. It highlights the need for more comprehensive monitoring of both livestock and wild herbivore populations in the Greater Himalaya, where these systems are understudied. Finally, limiting future increases in livestock grazing may be necessary to ensure the sustainable use of alpine meadows that support both wild herbivores and livestock.
Credit for all the images : Lisa Koetke
Link to the research paper : Koetke, L. J., T. Bhattacharya, and S. Sathyakumar. 2020. Diet overlap and competition between livestock and wild herbivores in the Himalayas. Mountain Research and Development, 40(1): R21-R27.
*The study was funded by a Fulbright-Nehru student grant and was conducted in affiliation with the Wildlife Institute of India, Dehradun.
Link to the research paper : Koetke, L. J., T. Bhattacharya, and S. Sathyakumar. 2020. Diet overlap and competition between livestock and wild herbivores in the Himalayas. Mountain Research and Development, 40(1): R21-R27.
*The study was funded by a Fulbright-Nehru student grant and was conducted in affiliation with the Wildlife Institute of India, Dehradun.
01/05/2021
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Lisa Koetke |
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Lisa’s research focuses on ungulate ecology, with an emphasis on understanding the impacts of anthropogenic disturbance on ungulate populations. She is currently a Ph.D. student at the University of Northern British Columbia, where she is studying the impact of forest harvesting on moose populations. She hopes to pursue a career in academia. Outside of work, she enjoys adventuring with her dog, particularly hiking, backpacking, and skiing in the mountains.
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