Sunday, 14 June 2015

First, Find Your Marmot

Rodents are, on the whole, small animals, with mice, voles, and squirrels being among the most familiar examples. Yet, even within those families, much larger animals also exist. In the mouse family, of course, there are the rats, some of which are, indeed, rodents of unusual size. The largest of the squirrels, on the other hand, are the marmots.

Marmots, of course, are ground squirrels, not the tree-dwelling sort, and their closest relatives include animals like prairie dogs, along with assorted other species across the Northern Hemisphere. They are, for the most part, mountain-dwelling species, with the groundhog of Canada and the eastern US being a well-known exception. Groundhogs, like other North American species, and, for that matter, the Alpine marmot of Europe, are a well studied species, about which we know a fair bit. The various species found across Asia - and there are at least six - are generally less well-known.

Among these is the Himalayan marmot (Marmota himalayana), perhaps the epitome of the mountain-dwelling marmots. While best known from the Himalayas themselves, it also inhabits a wide swathe of western China, spreading into Nepal and the most northerly reaches of India and Pakistan. They are generally absent from Tibet proper, aside from the Himalayas themselves and the Kunlun Mountains on the northern frontier, but are found across the eastern edge of the Tibetan Plateau, in Qinghai.

Aside from natural human curiosity, does it matter how much we know of the Himalayan marmot? It isn't even, to be honest, the most obscure of the marmots, for which one might want to look at some of the Siberian species. They seem, so far as we can tell, to be pretty common, and, when you add in the vast (if desolate) region that they inhabit, that means that we can hardly call them endangered.

Yet, like many animals, they are an important part of the local ecology. They are food, for one thing, being a particular favourite of the local brown bears, and also eaten by snow leopards. At the other end of the scale, like other small mammals, they may affect plant diversity, which, in turn affects the whole of the local ecosystem. Creatures living in mountainous regions may also be among those most affected by climate change, having nowhere to go but upwards onto ever smaller mountaintops, should the weather become warmer.

We do, of course, know the basics about Himalayan marmots and their lifestyles. They live above the treeline, in meadows dotted with shrubs, and in high altitude semi-desert grasslands, never venturing below about 3,000 metres (10,000 feet). They live in small colonies, digging burrows into the soil, and hibernating their way through the harsh winter. But that's about it, and if we want to more - if only to work out where endangered snow leopards will look for their supper - more detailed studies are, perhaps, warranted.

But how, exactly, do you do that? Let's take a look at a recently published survey examining the marmots and their diet at the northern end of the Annapurna Conservation Area in Nepal. This is a high altitude region of semi-desert grassland and mountain slopes surrounding the valley of the Kali Gandaki and the village of Lo Manthang close to the Chinese border. Part of Nepal since the 18th century, most of the locals speak Tibetan, rather than Nepali, and the valley was once part of a major trade route between India and Tibet.

Anyway, the first step in this sort of survey is to actually find the marmots. When you have an area of around 2,500 km2 (1,000 square miles), much of which is hard to get to, to search through, you really want a way to narrow this down a bit. The approach used by the researchers in this survey was to begin by asking the locals. Where did marmots live in their area? Were there less of them now than there used to be? Did they illegally hunt them?

Well, they denied that last bit, although it's hard to know whether they were being entirely honest, under the circumstances. In China, for instance, Himalayan marmots are hunted, for meat, fur, and sometimes as agricultural pests, so it's not unreasonable that Nepalese Tibetans might do the same. They did say that the population of marmots was in decline everywhere they knew about, but, in fairness, there could be reasons for that beyond illegal hunting - which was part of the point of the survey, after all.

But knowing where marmots could be found also gives some idea of what habitats they prefer. In this case, they were almost always close to water, and they preferred the warmer eastern and southern slopes of mountain valleys. Their burrows, once the researchers had gone and looked for them, were mostly in loose sandy soils, presumably that's the easiest sort to dig in.

The interesting point here, however, is that the process of digging the soils appeared to be mixing the soil, perhaps re-distributing its nutrients. This is one of the things that shows the importance of small animals to the overall ecology of a region, beyond the simple supply of food to larger carnivores. We already knew that Siberian marmots (M. sibirica) enhance the local plant life with their digging, something that can be particularly significant in an area with low rainfall and soils that might otherwise be of quite poor quality. So, while there was no definitive evidence of improved soil quality due to marmots in this study, it's a perfectly reasonable hypothesis that may need further examination.

To know exactly what plants marmots have been eating, there is, of course, only one way to be sure: examine their poo. Granted, you could just try watching them, but that might disturb the marmots, and you're bound to miss the odd nibble even if you can keep the watching up for hours at a time, which is unlikely. So poo it is. They do a lot of that sort of thing in zoology surveys.

Given that they live in grasslands, its perhaps unsurprising that a large part of their diet seemed to consists of sedges and similar grassy plants. However, they also had an apparent strong preference for Primula and cinquefoils during the spring and summer, when they would have been in flower. This indicates a mixed and balanced diet overall, but they tended to focus on plants that might be more nutritious - which, again, would make sense, especially in an arid habitat. They also ate more protein-rich plants in the spring, as they recovered from their long winter hibernation.

So what does this tell us? Himalayan marmots are clearly not narrow specialists, able to survive on only very particular foods or in very specific circumstances. On the other hand, while they are numerous now, there numbers do appear to be declining, at least in Nepal (and likely even more so in China, where they are widely hunted), and they do have clear preferences that suggest they can't survive equally well everywhere.

We're not going to run out of marmots any time soon; that isn't the point. But knowing where they live gives a good idea of where carnivores that are more endangered, and that rely on their presence, might seek them. Declining numbers might also affect the local plant life, both in terms of what is eaten, and what may rely on any improved soil quality they bring. And, as the Himalayas warm, conditions may change, and, in the longer term, that could have significant consequences.

[Photo by Christopher Fynn from Wikimedia Commons].

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