The Vancouver Island marmot (Marmota vancouverensis) is one of the largest members of the squirrel family (about the size of a large house cat). Other members of the Sciuridae family include chipmunks, squirrels and woodchucks.
Newborns have a uniformed brownish black coat that fades in summer to a rusty brown at hibernation time. These different colour stages of coat development make it easy to identify pups from yearlings and older adults in the field.
Marmots have large beaver-like teeth, sharp claws and powerful shoulder and leg muscles for digging. An adult Vancouver Island marmot typically measures 65-70 centimeters from nose to tip of its bushy tail. An average female weighs 4.5-5.5 kilos and males can weigh as much as 7.5 kilos. Both males and females lose up to 1/3 of their body mass in hibernation making seasonal weight variation from spring emergence to the onset of hibernation significant. They can turn from sleek to pump in a matter of a few months.
Vancouver Island marmots live in family groups called colonies and hibernate below ground from mid-September until late April or early May. Hibernation permits the marmots to survive the long alpine winters when food is not available.
Radio-telemetry suggests that marmots hibernate as family groups, and often re-use hibernacula in subsequent years. During hibernation the marmot’s heartbeat slows to 3 0r 4 beats per minute compared to an average range of 110-200 beats per minute when they are active. When they emerge from hibernation in the spring they often tunnel through several meters of snow.
During the active summer period, marmots spend a lot of their time lounging on rocks and watching for predators. Only a few hours each day are spent looking for food, eating and interacting with other marmots. Marmots are more likely to be seen in early morning or late afternoon than during the heat of the day.
Nose – touching (“greeting”) and play fighting (“boxing”) are common behaviours and very entertaining to watch. When alarmed, marmots give piercingly loud whistles, which earned them the nickname “Whistle Pig”. Vancouver Island marmots have five distinct whistles or trills used for different purposes. That’s more than any other marmot species.
Mating occurs below ground in May, shortly after waking from hibernation. Pups, usually 3 or 4 in a litter, are not seen above ground until late June or July. Females generally begin breeding at 3-4 years of age in the wild and generally produce a litter of pups every other year. They can live over 10 years in the wild (10-15 years in captivity), so a productive female might contribute 12-15 pups during her lifetime.
Both females and males are attentive parents, carefully guarding the nest burrow and otherwise standing guard: pups remain near their natal burrow for their first year and hibernate with their mother in late September. Yearlings generally expand their movements farther from home but usually return to hibernate with their mom a second time. Males will occasionally father pups with two or more females in a given year.
Habitat and Diet
Vancouver Island marmots live neither in the forest nor on the rocky mountaintops. They live in small patches of south and west-facing sub-alpine and alpine meadows (usually above 1000 meters), where occasional winter avalanches and snow creep prevent trees from taking root. These meadows are the first to become clear of snow and produce the early grasses and sedges the marmots rely upon when they emerge from hibernation.
There they find the forage they need, deep soil for digging (hibernation burrows need to be deep enough to reach below the frost line) and large boulders to provide convenient lookout spots to watch for predators. Boulders also help marmots regulate their internal body temperature; you will often see them stretched out on them in the early mornings and evenings, and are a predictable and necessary feature of marmot habitat.
Underground burrows provide shelter from the elements and protection from predators. Typically 30-45 cms across, burrows range in size and purpose. Small, simple burrows may be used for a quick escape from a predator and larger more complex burrows are used for hibernation and birthing and may have numerous passages and exits. One excavated hibernation burrow measured five meters in length with the sleeping chamber located one meter underground.
Hibernacula can be identified either by the grass and mud “plugs” found at tunnel entrances in late autumn, or by emergence tunnels through the snowpack in May or early June. In general, Vancouver Island marmots appear to select hibernacula that are covered during winter by deep snow.
Vancouver Island marmots are herbivores and are known to eat over 40 different species of grasses, herbs and wildflowers. Spring feasts begin with grasses, sedges and phlox and graduate to lupines and other forbs later in the season.
Vancouver Island marmot colonies are relatively small and can be made up largely of family members, contributing to a lack of mate selection. To avoid the effects constant inbreeding would have on the species, marmots increase their selection by leaving their natal colony to find a mate at a colony nearby or attract a mate dispersing from another colony.
This movement of marmots between colonies is called dispersal. Both male and female marmots disperse, usually as two year olds, although males are more common dispersers. One tracked male dispersed 27 kilometers looking for a mate! A more usual dispersal range is 5-20 kilometers.
In order for dispersing marmots to find potential mates there must be a healthy community of colonies within their dispersal range. These larger groups of colonies are called metapopulations. Marmots traveling between colonies allow new colonies to be formed and declining colonies to be replenished. This keeps the population healthy and provides an important safeguard for the species.
Spreading the marmots around in several smaller colonies guards against a total collapse of the species if any one colony should suffer a catastrophic event. Just like our grandmothers told us, “it isn’t wise to keep all your eggs in one basket.”