The Alpine Marmot Project

Welcome to the Alpine Marmot Project

Monitoring the Marmots

Monitoring of the population of marmots started in 1990.  Monitoring comprises two protocols, one  for capture, marking and recapture, and the other is the observation protocol.  Monitoring takes place very year, but the duration varies.  From less than 3 months in 1990 and 1991, it was extended up to 5 months (the entire period of marmot activity) between 1995 and 2000, and then limited by the authorities of the Vanoise National Park to 45 days since 2001. Monitoring is particularly intense during the breeding season, which begins with mating in mid-April and continues up until the emergence of marmot pups in mid-July.

The capture-mark-recapture protocol

Capture  

Among the many capture techniques tested, two, combining efficiency and minimal stress for individuals, were selected. Marmot adults are captured using humane traps and marmot pups may also be caught by hand as well.

trap
trap terminology

The marmots are caught with two-door lived captured traps (Tomahawk Live Trap Company, Wisconsin, USA). The traps are baited with dandelion which is placed on central trigger panel.  When the animal steps on this panel the trigger to close the doors is released.

These traps are used in two ways, for both voluntary capture and forced capture.

trap at work

Voluntary capture is by far the more frequent and easier method of capture. This involves deliberately placing traps on the marmots’ paths and principal burrows. Then appeal is made to the marmots’ universal gluttony and love for dandelions, and the cooperative nature of certain individuals.  Unfortunately the effectiveness of the voluntary method diminishes over the course of the marmots’ active season, and captures effected by this method are exceedingly rare in September.

We then turn to forced capture as a means of studying targeted individuals.  Forced capture involves scaring marmots so that they hide in their burrows, then blocking the majority of burrow exits and placing traps at the openings of those that remain.  This technique has two major drawbacks.  First of all, it is difficult to put into action, and relatively invasive.  Secondly, marmots have a strong preference for digging new exits rather than entering into a trap. The technique of forced capture is therefore only utilized at the end of the season.

Once baited traps are always checked every half hour.

Hand capture is reserved for marmot pups.  Researchers observe the burrow where marmot pups have been born and then grab the pups by hand as they emerge from the burrow. This technique is quick and extremely efficient (up to ten marmot pups can be captured each day), and allows researchers to target marmot pups and to capture the entire litter in a short period of time.  Nonetheless, this technique is useful only for those marmot pups which are still naive in the period following their first emergence into the outside world from the burrow in which they were born.

Marking the marmots

Both permanent, invisible tags, and less durable visual tags are used to distinguish and track individuals within the marmot population.

Permanent tags are systematically placed at the first capture. Two complementary types of tags are utilized:

– Microchip transponders are injected under their skin between the shoulder blades.  Each microchip carries a unique alphanumeric code with a maximum of 16 characters.  These microchips are read by an electronic reader which must be held within 30 cm of the marmot.  These chips are therefore read when the marmot is recaptured.
– Metal ear numbered ear tags are also placed on each marmot at capture.  They are put on the right ear on females, and the left ear on males.  These tags can be read through binoculars if the individual marmot is at a distance of less than 20 meters.  Reading these tags therefore calls for the recapture of the individual in most cases.  These tags last longer than two years in most cases.

transponder
ear tag

marked female

marked male

Two type of visual marks are also used to keep track of the marmots, but unfortunately neither one is permanent:

– Ammonia hair dye (L’Oreal) is used in both black and red  to make a mark on either as specific part of the body or in a unique shape to identify individuals.  This is very effective for visual recognition, but doesn’t last longer than four months.  The dye disappears when the marmots shed in the month of July.
– Colored ear tags are placed in the opposing ears of some adult marmots, that is the left ear for females, and the right ear for males.

Biometric measures and sampling

Once captured, individuals were anesthetized with an intramuscular injection.

Once anesthetized, individuals are sexed, weighed with a spring scale, then several biometric variables are measured with a measuring tape or caliper such as the total length of the marmot (head and body without the tail) the width of the front and back paws, the width of the jaw, the size of the head at the cheek bone, and the width of the pelvis.

Various samples are also taken at this time, such as blood samples, odor secretions, and in particular DNA samples necessary for DNA analysis.  Two techniques are used for obtaining DNA, up until 1996 only fur was sampled, since that year skin samples have been taken as well.

Observation protocol

In order to recognize the the socio-spatial structure of each of the family groups studied, the territory and the composition of family groups, as well as the social status of each individual is determined each year.  Furthermore, a particular effort is made to track reproductive events; this allows the researchers to determine the date that marmot pups will emerge from the burrow, as well as the size of the litter.