Mt. Cook fleas are not actually fleas, they are a type of wētā! They can live at heights where no other arthropod goes, at elevations up to 3,000m a.s.l., in permanently glaciated habitats! Their populations are found exclusively in the high alpine regions of the South Island of New Zealand, north of about Mt Cook (documented elevation range ~1,300m – 2,800m a.s.l., one individual was found 3,400m a.s.l. on Mt Cook!). It is often seen by climbers as it jumps from rock onto snow, in bright daylight. In this respect, it is unusual among cave wētā. While it is predominantly nocturnal, it is often active during the day, because its food sources (primarily lichen) are often frozen solid or encased in ice during the night. It can, however, be found foraging at temperatures below 0° C. It survives winter in the high alpine regions of the Southern Alps, in any life stage.
Check these links for more info on Mt Cook Flea in NZ
Wikipedia: Information on the Mt. Cook Flea
Click on the image to visit the official iNaturalist.nz observation.