project news

Social meltdown in Marmots

News item submitted by Jonathon Usherwood
News item dated 31 Jan 2011

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Recent research into a phenomenon, the ‘Allee Effect’, on the critically endangered Vancouver Island Marmot shows that population crashes can result in a dramatic weakening in social bonds.  The Vancouver Island Marmot, endemic to Vancouver Island in Canada, has undergone a dramatic population crash from 300 wild individuals in the 1970s to 36 today as a result of logging and increased predation. Marmots are social animals living in colonies consisting of several families. They graze open meadows near their burrows retreating into them at any signs of danger. As a result of the population crash the Marmot is undergoing ‘social meltdown’ progressing from a highly social animal towards a solitary existence. Colony sizes have become significantly smaller and the marmots show a much lower rate of social interactions. As a consequence of solitary living individuals must spend more time looking out for predators which means they have less time to feed. In addition marmots have been observed behaving uncharacteristically, for example crossing dangerous open areas in an attempt to find mates. All of these have drastic implications for marmot mortality from predation, reproductive rate and ability to hibernate. As a result the species would be heading towards extinction if it were not for an intensive captive breeding program. 

As sad as this is for this particular marmot species it has wider implications regarding the many endangered social animals. The Allee Effect can cause a breakdown in sociality in any endangered animal. This mean as they reach low population densities they suffer from decreased reproduction resulting in a downward spiral towards extinction.

Madagascar is home to 17 endangered lemur species many of which are highly social. One of these endangered lemurs is Sanford’s Brown Lemur found in the northern forests of Madagascar where volunteers from Frontier’s Madagascar Terrestrial Project are working. This research is looking at, amongst other things, the minimum size a forest fragment can be and still sustain a lemur population. There is a risk of the population size being limited by the forest size, and then Allee effect coming into play. This could therefore be a strong factor in both current and future conservation efforts.