Juergen Freund / Wildlife carer Margit Cianelli with juvenile Lumholtz kangaroo (Dendrolagus lumholtzi) with radio collar. The tree kangaroo has a radio collar to allow her to explore her forest surroundings ready for...

Juergen Freund / Margit Cianelli wildlife carer with young Lumholtz kangaroos (Dendrolagus lumholtzi), one with a radio collar. The tree kangaroo has a radio collar to allow her to explore her forest surroundings read...

Nick Garbutt / Pack of wolves (Canis lupus). Yellowstone National Park, Wyoming, USA. January.

Hugh Pearson / Leopard (Panthera pardus) resting, Erindi Game Reserve, Namibia.

Richard Du Toit / Two Lionesses fitted with radio tracking collars {Panthera leo} Chobe NP, Botswana

Juergen Freund / Radio collared Lumholtz's tree-kangaroo (Dendrolagus lumholtzi) 'Kimberley'. The radio collar allows this juvenile to explore the nearby forest before its eventual release. Lumholtz Lodge,...

Juergen Freund / Margit Cianelli with radio collared Lumholtz's tree-kangaroo (Dendrolagus lumholtzi) 'Kimberley'. The radio collar allows this juvenile to explore the nearby forest before its eventual rel...

Juergen Freund / Radio collared Lumholtz's tree-kangaroo (Dendrolagus lumholtzi) 'Kimberley'. The radio collar allows this juvenile to explore the nearby forest before its eventual release. Lumholtz Lodge,...

Juergen Freund / Lumholtz kangaroo (Dendrolagus lumholtzi) juvenile with radio collar, feeding on leaves inside house or wildlife carer Margit Cianelli. The tree kangaroo has a radio collar to allow her to explore her...

Juergen Freund / Lumholtz kangaroo (Dendrolagus lumholtzi) juvenile with radio collar, feeding on leaves inside house of wildlife carer Margit Cianelli. The tree kangaroo has a radio collar to allow her to explore her...

Juergen Freund / Wildlife carer Margit Cianelli with young year old Lumholtz tree kangaroo (Dendrolagus lumholtzi) with radio collar. This kangaroo was raised by Magrit who allows the juvenile to explore the forest re...

Juergen Freund / Lumholtz kangaroo (Dendrolagus lumholtzi) juvenile with radio collar, feeding on leaves inside house of wildlife carer Margit Cianelli. The tree kangaroo has a radio collar to allow her to explore her...

Nick Upton / Research team preparing to radio collar Siberian flying squirrel (Pteromys volans) caught in a trap. Muraka Forest Reserve, near Lisaku, Estonia. April 2018. Model released.

Nick Upton / Researcher examining and sexing Siberian flying squirrel (Pteromys volans) prior to fitting radio collar. Muraka Forest Reserve, near Lisaku, Estonia. April 2018. Model released.

Nick Upton / Siberian flying squirrel (Pteromys volans) fitted with radiocollar on Aspen (Populus tremula) trunk near nest hole. Mature mixed forest, near Lisaku, Estonia. April 2018.

Nick Upton / Siberian flying squirrel (Pteromys volans) in the hand, prior to fitting of radio collar. Muraka Forest Reserve, near Lisaku, Estonia. April.

Nick Upton / Researcher fitting radio collar on Siberian flying squirrel (Pteromys volans) caught in mature mixed forest at night. Near Lisaku, Estonia. April 2018.

Will Burrard-Lucas / Black and white image of African elephant (Loxodonta africana) with radio collar, Tsavo Conservation Area, Kenya. Editorial use only.

Will Burrard-Lucas / Black and white image of people fitting radio tracking collar onto African elephant (Loxodonta africana) Tsavo Conservation Area, Kenya. Editorial use only.

Will Burrard-Lucas / Black and white image of people fitting radio tracking collar onto African elephant (Loxodonta africana) Tsavo Conservation Area, Kenya. Editorial use only.

Will Burrard-Lucas / Black and white image of people fitting radio tracking collar onto African elephant (Loxodonta africana) Tsavo Conservation Area, Kenya. Editorial use only.

Will Burrard-Lucas / Black and white image of people viewed through sedated African elephant (Loxodonta africana) tusks during radio collaring operation. Tsavo Conservation Area, Kenya. Editorial use only.

Nick Garbutt / Jaguar (Panthera onca palustris) female yawning with mouth wide open, wearing Oncafari Project radio collar. Caiman Lodge, southern Pantanal, Mato Grosso do Sul, Brazil. September 2017.

David Perpinan / Vets attaching an ear transmitter to a male Brown bear (Ursus arctos) anaesthetised in Slovenia for a reintroduction project in the Pyrenees, Jelen Reserve, Slovenia, June, 2016.

Jeff Vanuga / Grizzly bear (Ursus arctos horribilis) trying to cross road with tourists looking on from vehicles, Grand Teton National Park, Wyoming, USA. May 2016.

Ashley Cooper / Yukon wolf (Canis lupus pambasileus) radio collared as part of a tracking program in the tundra, Denali National Park, Alaska, USA, September.

Tony Heald / African wild dog (Lycaon pictus) walking through grassland with radio collar showing. Mana Pools National Park, Zimbabwe.

Claudio Contreras / Scarlet Macaw (Ara macao) with radio transmitting collar, Scarlet Macaw reintroduction program, Palenque, Chiapas, southern Mexico, March

Enrique Lopez-Tapia / Cheetah (Acinonyx jubatus) female with radio transmitter collar, Kenya.

Enrique Lopez-Tapia / Cheetah (Acinonyx jubatus) female wearing radio tracking collar, Kenya.

Enrique Lopez-Tapia / Cheetah (Acinonyx jubatus) female wearing radio tracking collar, Kenya.

Sandesh Kadur / Indian rhinoceros (Rhinoceros unicornis) with radio collar, Manas National Park UNESCO World Heritage Site, Assam, India.

Hugh Pearson / Leopard (Panthera pardus) walking through dry grassland, Erindi Game Reserve, Namibia

Juan Carlos Munoz / Iberian lynx (Lynx pardinus) with radio collar, Extremadura, Spain, February

Juan Carlos Munoz / Iberian lynx (Lynx pardinus) with radio collar, Extremadura, Spain, February

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) wearing sloth backpack radio transmitter after release by Aviarios Sloth Sanctuary, Costa Rica.

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) being examined by Rebecca Cliff, Sloth Biologist, prior to putting on a sloth backpack radio collar before release, Aviarios Sloth Sanctuary, Cost...

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) being examined by Rebecca Cliff, Sloth Biologist, prior to putting on a sloth backpack radio collar before release, Aviarios Sloth Sanctuary, Cost...

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) being examined by Rebecca Cliff, Sloth Biologist, prior to putting on a sloth backpack radio collar before release, Aviarios Sloth Sanctuary, Cost...

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) being examined by Rebecca Cliff, Sloth Biologist, prior to putting on a sloth backpack radio collar before release, Aviarios Sloth Sanctuary, Cost...

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) wearing a sloth backpack radio transmitter being carried by Rebecca Cliff, Sloth Biologist, to a release site, Aviarios Sloth Sanctuary, Costa Ric...

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) wearing a sloth backpack radio transmitter travelling by boat with Rebecca Cliff, Sloth Biologist, to a release site, Aviarios Sloth Sanctuary, Co...

Suzi Eszterhas / Brown-throated Three-toed sloth (Bradypus variegatus) wearing a sloth backpack radio transmitter travelling by boat with Rebecca Cliff, Sloth Biologist, to a release site, Aviarios Sloth Sanctuary, Co...

Suzi Eszterhas / Rebecca Cliffe, Sloth Biologist, using transmitter to find tagged Brown-throated three-toed sloths and Hoffmann's two-toed sloths in forest canopy, Aviarios Sloth Sanctuary, Costa Rica. November 2014...

Suzi Eszterhas / Rebecca Cliffe, Sloth Biologist, using transmitter to find tagged Brown-throated three-toed sloths and Hoffmann's two-toed sloths in forest canopy, Aviarios Sloth Sanctuary, Costa Rica. November 2014...

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Andrew Walmsley / Javan slow loris (Nycticebus javanicus), foraging in the canopy. Adult wearing a radio collar, allowing scientists to study the local population. Cipaganti, Garut, Java, Indonesia.

Luke Massey / Iberian lynx (Lynx pardinus) released as part of the EU LIFE project, Sierra Morena, Spain

Cyril Ruoso / Chacma baboon (Papio ursinus) portrait with radio collar, Cape Peninsula, South Africa

Nick Upton / David Bavin using a radiotracker to locate radio-collared Pine martens (Martes martes) at night after release during a reintroduction project by the Vincent Wildlife Trust, Cambrian Mountains, Wales,...

Nick Upton / Radio-collared male Pine marten (Martes martes) preparing to emerge from a temporary soft release cage at night , during reintroduction project by the Vincent Wildlife Trust, Cambrian Mountains, Wales...

Denis-Huot / African elephant (Loxodonta africana) bull with a radio collar marking his territory by rubbing against a tree, Musiara Marsh, Masai Mara Game Reserve, Kenya.

Richard Du Toit / Cheetah (Acinonyx jubatus) with radio collar, Kalahari, Northern Cape Province, South Africa.

Juergen Freund / Spectacled flying fox (Pteropus conspicillatus) is anaesthetised before a radio collar is attached to its neck for scientific research. Atherton, Queensland, Australia.

Neil Aldridge / African wild dog (Lycaon pictus) wearing a radio collar on Venetia Limpopo Reserve, South Africa

Neil Aldridge / African wild dog (Lycaon pictus) wearing a radio collar resting amongst rocks on Venetia Limpopo Reserve, South Africa.

Nick Upton / Radio-collared female Pine Marten (Martes martes) foraging at night in woodland. Reintroduced to Wales by the Vincent Wildlife Trust. Cambrian Mountains, Wales, UK, May 2016. Photographed using a remo...

Nick Upton / Radio-collared female Pine Marten (Martes martes) foraging at night in woodland. Reintroduced to Wales by the Vincent Wildlife Trust. Cambrian Mountains, Wales, UK, May 2016. Photographed using a remo...

Nick Upton / Radio-collared female Pine Marten (Martes martes) reintroduced to Wales by the Vincent Wildlife Trust foraging at night in woodland, Cambrian Mountains, Wales, UK, May 2016. Photographed using a remot...

Staffan Widstrand / Elephant (Loxodonta africana) seen through window of safari car, with radio collar. iMfolozi National Park, South Africa

Jeff Vanuga / Rocky mountain bighorn sheep Rocky mountain bighorn (Ovis canadensis canadensis) ewe with tracking collar for identification. Whiskey Mountain near Dubois, Wyoming, USA, November.

Nick Upton / Sleepy, radio-collared Edible / Fat Dormouse (Glis glis) excavated from its winter hibernation burrow held during a survey in woodland where this European species has become naturalised, Buckinghamshi...

Nick Upton / Radio-collared Edible / Fat Dormouse (Glis glis) in its winter hibernation burrow, excavated during a survey in woodland where this European species has become naturalised, Buckinghamshire, UK, April.

Nick Upton / Sleepy Edible / Fat Dormouse (Glis glis) excavated from its winter hibernation burrow being weighed during a survey in woodland where this European species has become naturalised, Buckinghamshire, UK,...

Nick Upton / Exit tube fitted to the hibernation burrow of an Edible / Fat Dormouse (Glis glis) after replacing it during a survey in woodland where this European species has become naturalised, Buckinghamshire,...

Ole Jorgen Liodden / Polar bear (Ursus maritimus) with radio collar, calling on cliff in distance, with mountainous Svalbard landscape and clouds, Spitsbergen, Svalbard, January 2014.

Ole Jorgen Liodden / Polar bear (Ursus maritimus) with radio collar, feeding on seal on iceberg, Svalbard, Norway, July.

Lisa Hoffner / Elephant radio collars on the ground at sunrise, Samburu National Reserve, Kenya.

Lisa Hoffner / David Daballan with newly collared African elephant (Loxodonta africana) bull, Frank, waking up from the anaesthesia. Samburu National Reserve, Kenya. Taken with cooperation of Kenya Wildlife Service...

Lisa Hoffner / Save the Elephants employee preparing collar for elephant collaring, Samburu National Reserve, Kenya.

Lisa Hoffner / Save the Elephants employee preparing collar for elephant collaring, Samburu National Reserve, Kenya.

Lisa Hoffner / Iain Douglas-Hamilton with various elephant radio tracking collars used by Save the Elephants, Samburu National Reserve, Kenya. Model Released

Lisa Hoffner / Iain Douglas-Hamilton with various elephant radio tracking collars used by Save the Elephants, Samburu National Reserve, Kenya. Model Released

Lisa Hoffner / Iain Douglas-Hamilton with various elephant radio tracking collars used by Save the Elephants, Samburu National Reserve, Kenya. Model Released

Lisa Hoffner / Iain Douglas-Hamilton with various elephant radio tracking collars used by Save the Elephants in the Samburu National Reserve, Kenya. Model Released

Lisa Hoffner / Iain Douglas-Hamilton with various elephant radio tracking collars used by Save the Elephants, Samburu National Reserve, Kenya. Model Released

Lisa Hoffner / Gilbert Sabinga with radio tracking collars at the Save the Elephant camp, Samburu National Reserve, Kenya. Model Released

Lisa Hoffner / African elephant (Loxodonta africana) waking up after being tranquillized. Elephant from Samburu schools herd. Samburu National Reserve, Kenya. Taken with cooperation of Kenya Wildlife Service and Sav...

Lisa Hoffner / Save the elephants team collaring African elephant (Loxodonta africana) from the Samburu schools herd. Samburu National Reserve, Kenya. Model Released. Taken with cooperation of Kenya Wildlife Service...

Lisa Hoffner / Tom Haines Henderson, David Daballan and Dr. Rono Bernard with Kenya Wildlife Service ranger. Collaring African elephant (Loxodonta africana) from the Samburu schools herd. Samburu National Reserve, K...

Lisa Hoffner / Rebecca Sargent and Chris measuring African elephant 'Frank' (Loxodonta africana) foot during collaring operation. Samburu National Reserve, Kenya. Model Released. Taken with cooperation of Kenya Wild...

Lisa Hoffner / Save the Elephants team collaring African elephant (Loxodonta africana) 'Frank', Samburu National Reserve, Kenya. Model Released. Taken with cooperation of Kenya Wildlife Service and Save the Elephant...

Lisa Hoffner / Dr. Rono Bernard inspecting the trunk of African elephant (Loxodonta africana) bull, 'Frank' while collaring. Samburu National Reserve, Kenya. Model released.Taken with cooperation of Kenya Wildlife S...

Lisa Hoffner / Save the Elephants collared African elephant (Loxodonta africana) feeding, Samburu National Reserve, Kenya.

Lisa Hoffner / Save the Elephants collared African elephant (Loxodonta africana) Samburu National Reserve, Kenya.

Lisa Hoffner / Elephant radio collars at Save the Elephants research headquarters, Samburu National Reserve, Kenya.

Lisa Hoffner / Save the Elephants collared elephant (Loxodonta africana) drinking from a pool of water on a rocky outcrop, Samburu National Reserve, Kenya.

Solvin Zankl / Brown hyena (Hyaena brunnea) adult and pups outside den, Sperrgebiet National Park, Namibia, December.

Enrique Lopez-Tapia / Golden bamboo lemur (Hapalemur aureus) female wearing radio collar, feeding on bamboo. Ranomafana National Park, Madagascar. Critically Endangered species.