Axel Gomille / Wolf (Canis lupus) footprints, Saxony-Anhalt, Germany, August.

Axel Gomille / Wolf (Canis lupus) footprints in tire tracks, Saxony-Anhalt, Germany, August.

Axel Gomille / Wolf (Canis lupus) footprints, Saxony, Germany, July.

Axel Gomille / Wolf (Canis lupus) footprints, Saxony, Germany, August.

Ashley Cooper / Polar Bear footprints in melting permafrost on Northern Svalbard. July 2013

Sergey Gorshkov / Wolf (Canis lupus) paw print, Putoransky State Nature Reserve, Putorana Plateau, Siberia, Russia

Franco Banfi / Polar bear (Ursus maritimus) footprints compared to print from human shoe, Spitsbergen, Svalbard, Norway, Arctic Ocean.

Franco Banfi / Polar bear (Ursus maritimus) footprints, Spitsbergen, Svalbard, Norway, Arctic Ocean.

Bruno D'Amicis / Marsican / Abruzzo brown bear (Ursus arctos marsicanus) footprint next to human hand print. Critically endangered subspecies. Central Apennines, Abruzzo, Italy.

Dong Lei / Snow leopard (Panthera uncia) footprint on riverbank, Sanjiangyuan National Nature Reserve, Qinghai Hoh Xil UNESCO World Heritage Site, Qinghai-Tibet Plateau, Qinghai Province, China.

Bruno D'Amicis / Wild Apennine wolf (Canis lupus italicus) track in mud on a forest trail. Central Apennines, Abruzzo, Italy. September. Italian endemic subspecies.

Bruno D'Amicis / Wild Apennine wolf (Canis lupus italicus) tracks in snow. Central Apennines, Abruzzo, Italy. February.

Bruno D'Amicis / Wild Apennine wolf (Canis lupus italicus) rear paw track next to human hand print in snow. Central Apennines, Abruzzo, Italy. March.

Bruno D'Amicis / Wild Apennine wolf (Canis lupus italicus) tracks in frozen snow. Central Apennines, Abruzzo, Italy. March.

Bruno D'Amicis / Tracks of two Wild Apennine wolves (Canis lupus italicus) in frozen snow. Central Apennines, Abruzzo, Italy. March.

Bruno D'Amicis / Tracks of two Wild Apennine wolves (Canis lupus italicus) in frozen snow. Central Apennines, Abruzzo, Italy. March.

Ann & Steve Toon / Making a cast of an Indochinese tiger paw print (Panthera tigris corbetti), Thap Lan National Park, Thailand, August.

Ann & Steve Toon / Staff from NGO Freeland preparing to take a cast of an Indochinese tiger paw print (Panthera tigris corbetti), Thap Lan National Park, Thailand, August.

SCOTLAND: The Big Picture / Otter (Lutra lutra) tracks on beach, Sutherland, Scotland, UK, November

Philippe Clement / Pugmarks of Eurasian lynx (Lynx lynx) in melting snow, Bavarian Forest National Park, Germany, captive, February.

Roland Seitre / Spotted hyaena (Crocuta crocuta) footprints, Senegal.

Solvin Zankl / Brown hyena (Hyaena brunnea) footprint, Sperrgebiet National Park, Namibia, November.

David Tipling / Brown hare (Lepus europaeus) tracks in the snow, Norfolk, UK, January.

Nick Upton / Footprints of Water vole (Arvicola amphibius) or possibly Brown rat (Rattus norvegicus) on muddy river bank, found during survey for signs of Water voles, near Bude, Cornwall, UK, April.

Mark Taylor / Golden Retriever x Poodle 'F1b Goldendoodle' puppy on paw print background.

Fabio Liverani / Footprint of European brown bear {Ursus arctos} in the mud, Notranska, Slovenia

Fabio Liverani / Footprint of European brown bear {Ursus arctos} in the mud, Notranska, Slovenia

Igor Shpilenok / Kamchatka Brown bear (Ursus arctos beringianus) footprint in mud, Kamchatka, Kronostsky Zapovednik Reserve, Russia.

Dietmar Nill / Sand / Long nosed) viper {Vipera ammodytes} beside dog paw print, Bulgaria

Roland Seitre / Gray wolf (Canis lupus) tracks with evidence of mating, Ryazan, Oka Reserve, Russia.

Roland Seitre / Man looking at Gray wolf (Canis lupus) tracks, evidence of mating. Ryazan, Oka Reserve, Russia.

Doug Allan / Polar bear (Ursus maritimus) footprints over the sea ice, Spitzbergen, Svalbard, Norway.

Jenny E. Ross / Hind paw print of Kamchatka brown bear (Ursus actos) in sand, Bukhta Natalia, Koryaksky Nature Reserve, Kamchatka Peninsula, Russia.