Because hibernation begins in September, most marmots in Alaska spend two-thirds of each year locked in their winter dens.
(hibernation; begins; T:in September) (most marmots in Alaska; spend; two-thirds of each year; locked in their winter dens) (most marmots in Alaska; locked; L:in their winter dens)
hibernation most marmots in Alaska most marmots in Alaska
begins spend locked
T:in September
two-thirds of each year locked in their winter dens
L:in their winter dens