Kim Taylor / Southern flying squirrel {Glaucomys volans} taking off, Captive

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male sitting in tree, portrait. Hokkaido, Japan. March

Sergey Gorshkov / Northern goshawk (Accipiter gentilis) flying with squirrel prey, Finland . March

Sergey Gorshkov / Northern goshawks (Accipiter gentilis) fighting over squirrel carcass, Finland, March.

Stephen Dalton / Northern flying squirrel {Glaucomys sabrinus} gliding, controlled conditions, native to North America

John Waters / African Ground Squirrel {Xerus inaurus} two adults fighting, jumping in territorial dispute, Kalahari, North Cape, South Africa. Dove flying away.

Kim Taylor / Southern flying squirrel {Glaucomys volans} landing on tree trunk, Captive

Kim Taylor / Southern flying squirrel {Glaucomys volans} taking off, Captive

Benjam Pontinen / Siberian flying squirrel looking out of nest hole in tree {Pteromys volans} Finland, Europe

Benjam Pontinen / Siberian flying squirrels in nest {Pteromys volans} , Finland.

Benjam Pontinen / Siberian flying squirrel feeds in alder tree. Nurmo, Finland.

Yuri Shibnev / Siberian flying squirrel food hoard (Pteromys volans) Russia Ussuriland, South Primorskiy

Yuri Shibnev / Siberian flying squirrel (Pteromys volans) on tree trunk, Ussuriland, South Primorskiy, Far East Russia

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male feeding on Japanese alder (Alnus japonica) flower, perched on tree snag. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) on tree trunk beside nest hole. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) perched on tree snag. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) perched on tree snag after emerging from nest, nest lining material on squirrel's head. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) perched on branch. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male on branch, active during day due to competing for attention of female in oestrous. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) sitting on branch. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair mating on tree trunk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair mating on tree trunk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair mating on tree trunk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair mating on tree trunk, female putting up resistance, dislodging male. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair on tree trunk, male in pursuit of female, copulating and female returning to nest. Hokkaido, Japan. March. Digital composite sequence.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair, male in pursuit of female in oestrus, female spinning around to indicate she is not ready. Hokkaido, Japan. March. Digital composite sequenc...

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair on tree trunk at dusk, one peering out of nest, the other perched on branch. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) sitting on tree trunk at night near nest hole. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair on tree trunk, female in oestrus in nest hole, male sitting on guard above to fend off approaching males. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii), male attempting ambush attack on other, in competition over female in oestrus. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii), two males in competition during mating season, one feeding startled by other approaching on tree trunk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii), two males on tree trunk, one leaping on other in ambush during mating season. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) on tree trunk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male in tree. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male in tree. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male in tree, portrait. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male sitting in tree, portrait. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) grooming whilst sitting on branch. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) pair mating, crack in tree trunk is entrance to nest hole. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) grasping onto branch at dusk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) sitting on tree trunk outside nest hole at dusk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) emerging from nest hole at dusk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) sitting on branch in forest at dusk, after emerging from nest hole. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) peering out of nest hole in tree trunk. Hokkaido, Japan. March.

Tony Wu / Japanese dwarf flying squirrel (Pteromys volans orii) male gliding between trees. Hokkaido, Japan. March.

Nick Upton / Siberian flying squirrel (Pteromys volans) wearing a radiocollar sitting on a branch in mature mixed forest, near Iisaku, Estonia, April.

Nick Upton / Siberian flying squirrel (Pteromys volans) sitting on a branch in mature mixed forest, near Iisaku, Estonia, April.

Nick Upton / Siberian flying squirrel (Pteromys volans) defaecating from a branch in mature mixed forest, near Iisaku, Estonia, April.