Brian Bevan / Long tailed tit (Aegithalos caudates) nest building, Bedfordshire, England, UK, April.

Francois Savigny / African elephant feeding on thorn tree, Moremi, Botswana

Wim van den Heever / Ancient dead Camelthorn tree (Vachellia erioloba) trees with red dunes, Namib desert, Deadvlei, Sossusvlei, Namibia. August 2015.

Wim van den Heever / Ancient dead Camelthorn tree (Vachellia erioloba) trees with red dunes and mist, Namib desert, Deadvlei, Sossusvlei, Namibia. August 2015.

Wim van den Heever / Ancient dead Camelthorn trees (Vachellia erioloba) with red dunes, and star trails, Namib desert, Sossusvlei, Namibia. Composite.

Wim van den Heever / Ancient dead Camelthorn trees (Vachellia erioloba) with red dunes and the milky way behind, Namib desert, Sossusvlei, Namibia. Composite.

Wim van den Heever / Ancient dead Camelthorn trees (Vachellia erioloba) at night with red dunes behind. Namib desert, Sossusvlei, Namibia. Composite.

Wim van den Heever / Ancient dead Camelthorn trees (Vachellia erioloba) with sand dunes, Namib desert, Deadvlei, Sossusvlei, Namibia.

Wim van den Heever / Ancient dead Camelthorn trees (Vachellia erioloba) with sand dunes, Namib desert, Deadvlei, Sossusvlei, Namibia.

Pascal Pittorino / Mimosa (Acacia dealbata) flowers covered in snow , Var, Provence, France, February

David Kjaer / Duke of Burgundy butterfly (Hamearis lucina), Wiltshire, UK, June.

Enrique Lopez-Tapia / Spiny tree trunk (Pachypodium sp) Berenty Reserve, Madagascar.

Tony Phelps / Boomslang (Dispholidus typus) Immature male hunting in thorn bush above deHoop Vlei, Western Cape, South Africa, December

Nick Garbutt / Masai Giraffes (Giraffa camelopardalis) on open plains browsing Whistling Thorn Acacia (Acacia drepanolobium). Slopes of the Ngorongoro Highlands with the Serengeti Plains beyond, Tanzania. (Digitally...

Tony Heald / Eland (Taurotragus oryx) males locking horns and fighting. Devil's Thorn flowers (Tribulus terrestris) cover the ground. Etosha National Park, Namibia, January.

Tony Heald / Eland (Taurotragus oryx) male horning the ground which is covered in Devil's Thorn flowers (Tribulus terrestris). Etosha National Park, Namibia, January.

Tony Heald / Spotted Hyaena (Crocuta crocuta) rolling in Devil's Thorn flowers (Tribulus terrestris). Etosha National Park, Namibia, January.

Sharon Heald / Black-faced Impala (Aepyceros melamis petersi) male standing in a field of Devil's Thorn flowers (Tribulus terrestris). Etosha National Park, Namibia, January.

Tony Heald / Zebra (Equus quagga) foal running through Devil's Thorn flowers (Tribulus terrestris). Etosha National Park, Namibia, January.

Robert Thompson / Early thorn moth (Selenia dentaria) camouflaged as dead leaf on stem, Argory, County Armagh, Northern Ireland, UK, March

Alan Watson / Baobab tree (Adansonia rubrostipa) and Sogno (Didierea madagascariensis) in spiny forest, Reniala Reserve, Madagascar

Philippe Clement / Devil's thorn (Tribulus zeyheri) the Kalahari desert's prominent creeper, appearing after the rains, Kgalagadi NP, South Africa

Gerry Ellis / Whistling Thorn (Acacia drepanolobium) tree over savannah, Masai Mara National Reserve, Kenya

Mitsuaki Iwago / Masai Giraffe (Giraffa tippelskirchi) feeding on Whistling Thorn (Acacia drepanolobium) acacia tree, Serengeti National Park, Tanzania

Gerry Ellis / Whistling Thorn (Acacia drepanolobium) and moon, Amboseli National Park, Kenya

Mitsuaki Iwago / Whistling Thorn (Acacia drepanolobium) tree on savannah at sunset, Serengeti

Gerry Ellis / Umbrella Thorn (Acacia tortilis) trees at sunrise on savannah, Masai Mara, Kenya

Shin Yoshino / Whistling Thorn (Acacia drepanolobium) trees, Masai Mara National Reserve, Kenya

Mark Moffett / Ant (Pseudomyrmex sp) group drink nectar from Whistling Thorn (Acacia drepanolobium) acacia tree and protect the tree from leaf eating enemies ensuring mutual survival, Costa Rica

Mark Moffett / Ant (Pseudomyrmex sp) gathers carrot-like growths from Whistling Thorn (Acacia drepanolobium) acacia tree for delivery to larva in nest, in return for baby food, ant protects Acacia, Costa Rica

Mark Moffett / Ant (Pseudomyrmex sp) gathers carrot-like growths from Whistling Thorn (Acacia drepanolobium) acacia for delivery to larva in nest, in return for baby food Ant protects Acacia, Costa Rica

Anup Shah / Female patas monkey {Erythrocebus patas} feeding on acacia ants, Kenya.

Robin Chittenden / Great spotted cuckoo (Clamator glandarius) perched in thorny bush. Cyprus. April.

Andy Rouse / Grasshopper warbler (Locustella naevia) male singing in spring, UK, March.

Edwin Giesbers / Thorny burnet (Sarcopoterium spinosum) Cyprus. April.

Edwin Giesbers / Orange wattle (Acacia saligna) hanging branches with flowers and leaves. Cyprus. April.

Edwin Giesbers / Orange wattle (Acacia saligna) hanging branches with flowers and leaves. Cyprus. April.

Edwin Giesbers / Pyramidal orchid (Anacamptis pyramidalis) flowerhead amongst thorns. Cyprus. April.

Nick Upton / Horned treehopper / Thorn-hopper (Centrotus cornutus) on nettle stem at the edge of a meadow, Wiltshire, UK, May.

Nick Upton / Horned treehopper / Thorn-hopper (Centrotus cornutus) on nettle stem at the edge of a meadow, Wiltshire, UK, May.

Steven David Miller / Sulphur-crested cockatoo (Cacatua galerita) feeding on seedpods in Flax wattle (Acacia linifolia) tree. Lane Cove National Park, Sydney, New South Wales, Australia.

Sandesh Kadur / Black heron (Egretta ardesiaca) perched in thorny tree, Lake Manyara, Lake Manyara National Park, Tanzania.

Robin Chittenden / Orange swift moth (Triodia sylvina) Norfolk, England, UK. August

Staffan Widstrand / Wild Wonders of China / Close up of a plant with sharp barbs, Tongbiguan Nature Reserve, Dehong prefecture, Yunnan province, China, May.

Tony Heald / Elephant (Loxodonta africana), male standing on hind legs to reach acacia pods with Cattle egrets (Bubulcus ibis) in background. Mana Pools National Park, Zimbabwe.

Tony Heald / Elephant (Loxodonta africana), male standing on hind legs to reach acacia pods. Cattle egrets (Bubulcus ibis) around elephant's feet. Mana Pools National Park, Zimbabwe.

Tony Heald / Elephant (Loxodonta africana) shaking tree for acacia pods with forest in background. Mana Pools National Park, Zimbabwe. November 2017.

Rod Williams / Thorns on a bramble (Rubus fruticosus) Brockley Cemetery, Lewisham, London, England, UK. May.

Jen Guyton / Sunset over the Camelthorn trees (Vachellia erioloba) in the Kalahari Desert, South Africa.

Jen Guyton / Sunset over the Camelthorn trees (Vachellia erioloba) in the Kalahari Desert, South Africa.

Nick Upton / Marsh thistle (Cirsium palustre), white form, flowering in a damp woodland, Wiltshire, UK, June.

Adrian Davies / Thorn apple (Datura stramonium) seed pod.

Adrian Davies / Thorn apple (Datura stramonium) flowers opening, Surrey, England, UK. August.

Emanuele Biggi / Camel thorn tree (Acacia erioloba) half dead and close to dune, Sossusvlei area, Namib-Naukluft National Park, Namib Desert, Namibia

Emanuele Biggi / Deadvlei with dead Camel thorn tree (Vachellia erioloba) trees Namib-Naukluft National Park, Namib Desert, Namibia

Emanuele Biggi / Sand dunes and Acacia trees, Sossusvlei, Namibia, June 2017.

Emanuele Biggi / Sossusvlei's dunes and acacia trees, Sossusvlei area, Namibia, January 2017.

Emanuele Biggi / Dead Camelthorn trees (Vachellia erioloba) on sand, Deadvlei, Sossusvlei, Naukluft National Park, Namib Desert, Namibia, June.

David Kjaer / Purple thorn moth (Selenia tetralunaria) Dorset, England, UK, July.

David Kjaer / Early thorn moth (Selenia dentaria) on leaf, Dorset, England, UK, July.

David Kjaer / Canary-shouldered thorn moth (Ennomos alniaria) Wiltshire, England, UK, August.

Ernie Janes / Deadvlei with dead Camel thorn trees and tall sand dunes, Namib-Naukluft National Park, Namib Desert, Namibia

Ernie Janes / Deadvlei with dead Camel thorn trees, Namib-Naukluft National Park, Namib Desert, Namibia

Ernie Janes / Deadvlei with dead Camel thorn trees (Vachellia erioloba), Namib-Naukluft National Park, Namib Desert, Namibia

Paul Bertner / Treehopper (Membracidae)mimicking a thorn, Udzungwa Mountains National Park, Tanzania

Adrian Davies / Ancient dead Camelthorn trees (Vachellia erioloba) and dry river bed, Sossusvlei, Namib Desert, Namibia

Ingo Arndt / Sunrise in the Masai Mara National Reserve, with Whistling Thorn (Acacia drepanolobium) tree in picture, Kenya

Ingo Arndt / Acacia tree at sunrise on savannah, Masai Mara Game Reserve, Kenya

Frederique Olivier / Close-up of an African bush elephant (Loxodonta africana) feeding, stripping vegetation from an Acacia tree with its trunk, Serengeti NP, Tanzania.

Frederique Olivier / African bush elephants (Loxodonta africana) feeding, stripping vegetation from an Acacia tree with its trunk, Serengeti NP, Tanzania.

Charlie Summers / Flat top acacia tree (Acacia abyssinica) damaged by elephants. Elephants get moisture by feeding on the bark.

Paul Hobson / Purple thorn moth (Selenia tetralunaria) newly emerged leaf, Sheffield, England, UK, May.

Paul Hobson / Early thorn moth (Selenia dentaria) at rest on hawthorn, Sheffield, England, UK, April.

Francois Savigny / Striped skink {Mabuya striata sparsa} on camel thorn tree, Kalahari Gemsbok, South Africa

Jiri Lochman / Plant biodiversity on stabilized coastal dunes with Shark Bay Rose (Diplolaena grandiflora) and Sandhill Wattle (Acacia ligulata) in the foreground, Shark Bay UNESCO Natural World Heritage Site, Weste...

Jen Guyton / Thorny trunk of a cultivated silk floss tree (Chorisia speciosa), originally from South America, in Pietermaritzburg, South Africa.

Jen Guyton / Yellow devil's thorn flower (Tribulus zeyheri) in the Kalahari Desert, South Africa

Jen Guyton / Nest of sociable weavers (Philetairus socius) hangs from a thorn tree in the Namib Desert, Namibia. February 2015

Jen Guyton / Nest of sociable weavers (Philetairus socius) hangs from a thorn tree in the Namib Desert, Namibia.

Jen Guyton / Meerkat (Suricata suricatta) standing among a field of Devil's thorn flowers (Tribulus zeyheri) in the Kalahari Desert, South Africa.

Jen Guyton / Meerkats (Suricata suricatta) two look out over a field of Devil's thorn flowers (Tribulus zeyheri) in the Kalahari Desert, South Africa.

Jen Guyton / Meerkats (Suricata suricatta) four looking out over a field of Devil's thorn flowers (Tribulus zeyheri) Kalahari Desert, South Africa.

Jen Guyton / Meerkat pup (Suricata suricatta) standing among its family in a field of Devilthorn flowers (Tribulus zeyheri). Kalahari Desert, South Africa.

Jen Guyton / Meerkat (Suricata suricatta) two pups playing among a field of yellow devil's thorn flowers (Suricata suricatta) in the Kalahari Desert of South Africa.

Jen Guyton / Meerkat (Suricata suricatta+ two pups huddle among a field of yellow devil's thorn flowers (Suricata suricatta) in the Kalahari Desert, South Africa.

Jen Guyton / African monarch butterfly (Danaus chrysippus) sipping nectar from a Devil's thorn flower (Tribulus zeyheri) in the Kalahari Desert, South Africa.

Jen Guyton / Rainbow above Umbrella thorn acacia (Vachellia tortilis) Serengeti National Park, Tanzania.

Luke Massey / Acacia logs being transported, Balikpapan, Indonesia

Luke Massey / Acacia logs being transported, Balikpapan, Indonesia

Luke Massey / Acacia logs being transported, Balikpapan, Indonesia

Tony Heald / Egyptian goose (Alopochen aegyptiaca) pair amongst Devil's-thorn yellow flowers (Tribulus terrestris) Etosha National Park, Namibia, March.

Tony Heald / White-backed vulture (Gyps africanus) sunbathing amongst Devil's-thorn yellow flowers (Tribulus terrestris), Etosha National Park, Namibia, March.

Tony Heald / Klein Okevi waterhole covered by Devil's-thorn yellow flowers (Tribulus terrestris) Etosha National Park, Namibia, March 2016

Tony Heald / Black-faced impala (Aepyceros melampus petersi) young male Lying in Devil's-thorn yellow flowers (Tribulus terrestris) Etosha National Park Namibia, March.

Tony Heald / Black-faced impala (Aepyceros melampus petersi) female leaping above Devil's-thorn yellow flowers (Tribulus terrestris) Etosha National Park, Namibia.