Aflo / Japanese flying squirrel (Petaurista leucogenys) in tree hole, Kyoto, Japan. March.

Jussi Murtosaari / White-backed woodpecker (Dendrocopos leucotos) male on heavily drilled tree, Laukaa, Keski-Suomi, Lansi- ja Sisa-Suomi / Central and Western Finland, Finland. February

Rhonda Klevansky / Hole in the salt pan of Salar de Uyuni, the worlds biggest salt pan, Bolivian Altiplano, Bolivia. February 2009.

Rhonda Klevansky / Tourist standing by hole in Salar de Uyuni, the worlds largest salt pan, Altiplano, Bolivia. February 2009.

David Noton / Dawn over the mountains and Nam Song River at Vang Vieng, Laos, March 2009.

Olga Kamenskaya / Hole in ice used by Baikal seals (Pusa sibirica) for breathing. Lake Baikal, Russia, April.

Olga Kamenskaya / People looking at hole in ice used by Baikal seals (Pusa sibirica) for breathing. Lake Baikal, Russia, April 2009.

Olga Kamenskaya / Hole in ice used by Baikal seals (Pusa sibirica) for breathing. Lake Baikal, Russia, April.

Olga Kamenskaya / Holes in ice used by Baikal seals (Pusa sibirica). Lake Baikal, Russia, April 2009.

Olga Kamenskaya / Man visible on surface of the ice through dive hole. Lake Baikal, Russia. March 2008.

Pal Hermansen / View to wintry landscape through hole in ice, Hornsund, Svalbard, Norway, September.

Philippe Clement / European pine marten (Martes martes) emerging from its nest hole in a tree in autumn, Bayerischer Wald / Bavarian Forest National Park, Germany, October. Captive. Digital composite.

Nick Garbutt / Hole chewed in tree trunk by a feeding Aye-aye (Daubentonia madagascariensis) excavating for beetle grubs. In forests near Andranotsimaty, Daraina, northern Madagascar.

Nick Garbutt / Holes chewed in tree trunk by a feeding Aye-aye (Daubentonia madagascariensis) excavating for beetle grubs. In the forests near Andranotsimaty, Daraina, northern Madagascar. Endangered species.

Fabrice Cahez / Forest reflected in bubble from small puddle, Vosges, France, May.

Jan Hamrsky / Lesser silver water beetle (Hydrochara caraboides) with bubble of air on its underside, Europe, June, controlled conditions

Olga Kamenskaya / Lines of bubbles caught in ice of Lake Baikal, Siberia, Russia, March.

Nick Upton / Mat of Green freshwater algae blooming on a damp draincover, releasing oxygen bubbles through photosynthesis, Wiltshire, UK, May.

Loic Poidevin / Black woodpecker (Dryocopus martius ) at nest hole, with chicks begging for food, Indre-et-Loire, France, June.

Loic Poidevin / Black woodpecker (Dryocopus martius ) at nest hole, Indre-et-Loire, France, June.

Konrad Wothe / Tarantula (Pamphobeteus antinous) Tambopata National Reserve, Peru, South America.

Konrad Wothe / Tarantula (Pamphobeteus antinous) at hole, Tambopata National Reserve, Peru, South America.

Chris & Monique Fallows / Cape Gannets (Morus capensis) diving underwater to feed on sardines, Port St Johns, Transkei, South Africa.

Enrique Lopez-Tapia / DUPLICATE DELETE Icebergs with holes in the ice, Iceberg Alley, Pleneau Island, Antarctica.

Nick Upton / Jackdaw (Corvus monedula) standing at the entrance to its nest hole in a pollarded willow trunk, Gloucestershire,UK, April.

Nick Upton / Jackdaw (Corvus monedula) standing at the entrance to its nest hole in a pollarded willow trunk, Gloucestershire,UK, April.

Alex Mustard / Pygmy cancer crab (Cancer oregonensis) makes its home in a hole within a yellow sponge. Browning Pass, Port Hardy, Vancouver Island, British Columbia, Canada. North East Pacific Ocean.

Alex Mustard / Pygmy cancer crab (Cancer oregonensis) makes its home in a hole within a yellow sponge. Browning Pass, Port Hardy, Vancouver Island, British Columbia, Canada. North East Pacific Ocean.

Alex Mustard / Mosquito larva (Culicidae) in a shallow pool filled with vegetation. Giara GiarDi Gesturi National Park, Sardinia, Italy.

Jan Hamrsky / Water spider (Argyroneta aquatica) detail of air bubble around its abdomen, Europe, July, controlled conditions

Jan Hamrsky / Water spider (Argyroneta aquatica) refilling its air supply, Europe, July, controlled conditions

Jan Hamrsky / Water spider (Argyroneta aquatica) with air bubble, Europe, July, controlled conditions

Markus Varesvuo / Willow grouse (Lagopus lagopus) snow hole, Utsjoki, Finland, April.

Markus Varesvuo / Rock ptarmigan (Lagopus muta) snow hole, Utsjoki, Finland, April.

Theo Bosboom / Close up of leaves (probably of purple moor grass) and bubbles captured in the ice, Deeler Woud Nature Reserve, the Netherlands, January

Orsolya Haarberg / Ice formations with air bubbles frozen under ice. Helgeland, Norway. January 2010

Orsolya Haarberg / House entrance with fish hung up to dry. Vevelstad, Helgeland, Nordland, Norway September 2008