Summary: Hut & Scharff (1998)

Endoscopic equipment can be used to observe the behaviour of ground-dwelling animals inside their burrows. Hut & Scharff (1998) used a 205cm manoeuvrable fibre optic industrial endoscope attached to a video system to assess tunnel-blocking behaviour in European ground squirrels Spermophilus citellus. They found that, in 82% of cases, a tunnel block was found approximately 57 cm from the tunnel entrance. They suggest that ground squirrels are actively avoiding under-ground predation by blocking the tunnels with sand, and that they do this when both entering and leaving the burrow. Hut & Scharff (1998) suggest that these squirrels likely show a high tolerance to low oxygen (hypoxia) and high carbon dioxide (hypercapnia) conditions.

Summary: Blumstein et al. (2004)

Blumstein et al. (2004) investigated social hibernation in yellow-bellied marmots (Marmota flaviventris), as the species has a harem/polygynous social system, by monitoring emergence patterns from hibernation. Females share burrows and show home-range overlap in summer. They found that, as for 14 other species of the marmots, yellow-bellied marmots are social hibernators. They indicate that, although they hibernate socially, they might not accrue benefits of social thermoregulation. Blumstein et al. (2004) suggest that emergence times are occurring earlier in the year, consistent with global climate change models that suggest an influence of climate change on hibernation patterns in sub-alpine areas.