It’s not known exactly when the first marmot ancestors arrived. They may have crossed over to the island as early as the Illinoian glacial period (about 100,000 years ago) or more recently during the Cordilleran glaciation (10,000 years ago). Sea levels fell during both of these periods creating land bridges between the mainland and Vancouver Island allowing marmots from the continent to travel to the newly accessible island. Once the glaciers melted sea levels rose again, isolating the island marmots and setting the stage for a new species to evolve.
Separated from the other marmots on the mainland of North America, the Vancouver Island marmot developed into a distinct species. Historic and prehistoric records suggest a more widespread population and range in the past that allowed the species to persist for thousands of years. Ancient marmot bones have been found in several caves on Vancouver Island, carbon dated at 9,400 years old, but actual historic population levels can only be guessed at.
A Declining Population
Vancouver Island marmots had disappeared from about two-thirds of their historic natural range. Once distributed in alpine meadows throughout Vancouver Island, the marmot population rapidly declined in the mid 1990s. By 1998, only 70 marmots were recorded in the wild, and with the exception of one lone colony on Mt Washington, all marmots were located in one small geographic area east of the Nanaimo Lakes.
The Mt Washington colony was the only surviving colony in the central and northern regions of the marmot’s historic habitat and the remaining marmot population south of Alberni Inlet was so small and fragmented that dispersing animals were unable to find mates. The Recovery Team determined that without active human intervention (captive breeding followed by the reintroduction of captive-bred animals back to the wild) the species would become extinct in the very near future.
We will never know with certainty why marmots disappeared from Strathcona Provincial Park and surrounding regions. In stark contrast to the southern core, Strathcona Provincial Park is the largest protected area containing marmot habitat on Vancouver Island and has been identified as an important area for recovery of the species. So why, if the Park was largely untouched by industrial activity, did the marmots there become extinct?
The question may be best answered by what we have learned about marmot mortality in the south, where radio telemetry has identified predation as the most significant cause of recent mortality. From 1995-2005, predation by wolves (Canis lupus), cougars (Felis concolor) and golden eagles (Aquila chrysaetos) accounted for 80% of marmot mortality.
Research suggested that abnormally high levels of predation led to dramatic declines at some colonies in just a single year, and showed that colony-specific survival rates were spatially correlated (similar at closer locations) indicating that declines may have been caused by localized predation events. But predation is a natural and ongoing process the marmots have always been exposed to – so what changed?
It’s has been speculated that ongoing landscape changes on the Island had coinciding impacts on predator and prey populations as well as on Vancouver Island marmot populations. The boom and bust population dynamics of predators and prey may have been much more extreme over recent decades, exacerbated by the constraints of an island environment. In years with greater numbers of predators and fewer prey, this could have shifted “unnatural” pressures onto marmot populations.
Vancouver Island marmots were never plentiful enough to be the sole prey species for a predator population due to the scarcity of their habitat. Instead, marmots functioned as secondary prey species, and were killed opportunistically while predators hunted more plentiful species such as elk, deer or rabbit. But the impacts of an “unbalanced” predator-prey relationship may have been enough to drive this uniquely Canadian species to the brink of extinction.
Radiotelemetry will help us to answer some of our remaining questions. Marmots in the wild have radiotelemetry transmitters which send out pulses that our crew can detect using special equipment. The strength of the pulse helps us to track a specific location, and the speed of the pulse tells our crew whether the marmot is alive, dead, or hibernating. When a marmot has died, we retrieve its transmitter, and clues around the transmitter help us to determine its “cause of death”.
While predation was a daunting hurdle to overcome in the south, persistent releases have enabled the marmots to “get ahead” of the predation rate. Since predation mortality did not increase with the growing marmot population, marmot colonies were able to persist and grow, helping the southern population to recover. Extreme weather conditions, especially in the spring, have played a significant role in the mortality of captive-born marmots released to the wild when experiencing their first hibernation. This was particularly true for captive-born marmots released in 2009 and 2010. Those winters brought high levels of snow and were followed by a prolonged cold spring, limiting the marmots’ access to vegetation for several weeks after emergence.
However, extreme weather conditions so not appear to negatively impact wild-born marmots, and we have even documented high reproduction in years where the snow melted late. It also seems that once a captive-born marmot survives its first wild hibernation, it survives equally well as wild-born marmots. So, while the extreme weather events of the past few years have slowed the recovery results in the northern and central regions, where the majority of releases were concentrated during those years, it does not indicate that weather events lead to the collapse of the wild population.