Eric Baccega / African elephant (Loxodonta africana) feeding on acacia thorn bush, Samburu National Reserve, Kenya, Africa.

Jouan Rius / Top of Saguaro cactus (Carnegiea gigantea) backlit showing thorns, Saguaro National Park, Arizona, USA, December 2012.

Wild Wonders of Europe / Widstr / Jerusalem Thorn (Paliurus spina-christi) Sakar Mountains, Eastern Rhodope Mountains, Bulgaria, May 2013.

Wild Wonders of Europe / Widstr / Crown of Thorns (Paliurus spina-christi) bush, grazed by Fallow deer (Dama dama) Studen Kladenets reserve, Eastern Rhodope Mountains, Bulgaria, May 2013.

Wild Wonders of Europe / Widstr / Crown of Thorns (Paliurus spina-christi) bush, grazed by Fallow deer (Dama dama) Studen Kladenets reserve, Eastern Rhodope Mountains, Bulgaria, May 2013.

Dr. Axel Gebauer / Rosa omeiensis (Rosa omeiensis) stem showing thorns, Gonggai Shan Nature Reserve, Kangding / Dartsedo, Tibet, China, August.

Juergen Freund / Thorny stem of a rattan palm (Calameae) in the forest. Tangkoko National Park, North Sulawesi, Indonesia

Juergen Freund / Rattan plants in the forest. Bako National Park, Sarawak, Malaysian Borneo

Juergen Freund / Rattan plant spines in the forest. Bako National Park, Sarawak, Malaysian Borneo.

D. Parer & E. Parer-Cook / Atlantic Trumpet Triton (Charonia tritonis) feeding on Crown-of-thorns Starfish (Acanthaster planci), Great Barrier Reef, Queensland, Australia

Juergen Freund / Fine needles of a stinging tree leaf on nettle tree (Dendrocnide excelsa) Atherton Tablelands, Queensland, Australia

Denis-Huot / Tree with trunk covered with spines (Ceiba sp) in tropical forest, Corcovado National Park, Costa rRca

Denis-Huot / Whistling thorn (Acacia drepanolobium) galls occupied by mutualist ant (Crematogaster sp) Kenya

Denis-Huot / Whistling thorn (Acacia drepanolobium) gall occupied by mutualist ant (Crematogaster sp) Masai Mara, Kenya

Denis-Huot / Whistling thorn (Acacia drepanolobium) gall occupied by mutualist ants (Crematogaster sp) Kenya

Denis-Huot / Whistling thorn (Acacia drepanolobium) gall occupied by mutualist ant (Crematogaster sp) Kenya

Juan Manuel Borrero / Illustration of Jerusalem thorn (Paliurus aculeatus). Pencil and watercolor painting.

Alex Hyde / Bramble (Rubus plicatus) backlit close up of thorn, UK

Nick Upton / Stemless / Dwarf carline thistle / Silver thistle (Carlina acaulis) with single large flower bud at 1800m in the Julian Alps, Triglav National Park, Slovenia, July

Nick Upton / Stemless / Dwarf carline thistle / Silver thistle (Carlina acaulis) with single large flower bud at 1800m in the Julian Alps, Triglav National Park, Slovenia, July

Pete Oxford / Turk's Cap cactus (Melocactus macracanthos) Slagbaai National Park, Bonaire, Netherlands Antilles, Caribbean

Hanne & Jens Eriksen / Southern grey shrike (Lanius meridionalis) perched on dry thorny twig, Oman, January

Hanne & Jens Eriksen / Southern grey shrike (Lanius meridionalis) perched on dry thorny twig, Oman, January

Alex Hyde / Raft Spider (Dolomedes fimbriatus) juvenile on thistle stem. Naturpark Kaunergrat, Nordtirol, Tirol, Austian Alps, July.

Jeff Rotman / Crown-of-thorns starfish (Acanthaster planci) grazing on coral at night, Red Sea, Egypt

Markus Varesvuo / Barred Warbler (Sylvia nisoria) perched in thorns by a rosehip. Finland, May.

Juergen Freund / Tubbataha Reef rangers collecting thousands of Crown-of-thorns starfish (Acanthaster planci), an invasive species that has spread in the lagoon in epidemic proportions. Tubbataha Reef National Marine...

Juergen Freund / Crown-of-thorns starfish (Acanthaster planci) in the reef. Tubbataha Reef rangers collect thousands of these invasive animals which have spread in the lagoon in epidemic proportions. Tubbataha Reef Na...

Juergen Freund / Crown-of-thorns starfish (Acanthaster planci) collected by a snorkeler. Tubbataha Reef rangers collect thousands of these invasive animals which have spread in the lagoon in epidemic proportions. Tub...

Nick Upton / Jerusalem thorn / Christ's thorn / Crown of thorns tree (Paliurus spina-christi) with clusters of yellow winged fruits / seed pods growing on coastal limestone hillside, Zadar province, Croatia, July.

Nick Upton / Keeled, winged seed pods of Jerusalem thorn / Christ's thorn / Crown of thorns tree (Paliurus spina-christi) against blue sky, growing on coastal limestone hillside, Zadar province, Croatia, July.

Nick Upton / Keeled, winged seed pods of Jerusalem thorn / Christ's thorn / Crown of thorns tree (Paliurus spina-christi) growing on coastal limestone hillside, Zadar province, Croatia, July.

Sergey Gorshkov / African scops owl (Otus senegalensis) perched on Acacia tree at night, Okavango delta, Botswana, April

Markus Varesvuo / Yellow browed warbler (Phylloscopus inornatus) perched on stem, Finland, October

Markus Varesvuo / Pallas's leaf warbler (Phylloscopus proregulus) perched, Finland, October

Nick Upton / Blackthorn (Prunus spinosa) blossom and thorns, close-up detail. Wiltshire, UK, April.

Murray Cooper / Kapok (Ceiba sp) thorns on trunk, Ecuador

Philippe Clement / Sea-buckthorn (Hippophae rhamnoides) thorns and buds opening, Belgium

David Kjaer / Grasshopper Warbler (Locustella naevia) singing in wild rose bush, Wiltshire, England, UK. May

Hanne & Jens Eriksen / Arabian gazelle {Gazella gazella} reaching up to feed on acacia, after rain in the desert, Oman

Hanne & Jens Eriksen / Arabian gazelle {Gazella gazella} reaching up to feed on Acacia, Oman

Hanne & Jens Eriksen / African silverbill {Lonchura cantans} perched, Oman, January

Hermann Brehm / Ashy starling (Cosomopsarsus unicolor) calling, perched in Acacia tree, Africa

Hermann Brehm / Superb starling (Lamprotornis superbus) perched in Acacia tree, Africa.

Hermann Brehm / Superb starling (Lamprotornis superbus) perched in Acacia tree, calling, Africa.

Stephen Dalton / Mud dauber wasp (Sceliphron caementarium) in flight over cactus spines, Everglades, Florida. Controlled conditions.

Stephen Dalton / Spear thistle (Cirsium vulgare) flower, UK

Anup Shah / Superb starling (Lamprotornis superbus) perching on thorny branch, Masai Mara National Reserve, Kenya. March

Juergen Freund / Close up of spines of Crown-of-Thorns starfish (Acanthaster planci) Great Barrier Reef, Australia

Juergen Freund / Close up of Crown-of-Thorns Starfish (Acanthaster planci) feeding on Acropora coral, Great Barrier Reef, Australia.

Juergen Freund / Crown-of-Thorns Starfish (Acanthaster planci) feeding on Acropora coral, Great Barrier Reef, Australia.

Stephen Dalton / Red-billed hornbill (Tockus erythrorhynchus) perched on Acacia, Africa

Sue Daly / Crown of Thorns starfish (Acanthaster planci) on hard coral, Cebu, Philippines, March

Sue Daly / Crown of Thorns starfish (Acanthaster planci) on hard coral, Cebu, Philippines, March

Ross Hoddinott / Backlit rose thorn, Broxwater, Cornwall, UK. October.

Robert Thompson / Caterpillar larve of the Dusky thorn moth {Ennomos fuscantaria} camouflaged as thorn, UK

Graham Eaton / Rock Pipit (Anthus petrosus) perched on bramble, Abersoch, Wales, UK, June

Jeff Rotman / Arm and tubed feet of Crown of thorns starfish (Acanthaster planci) at night, Red Sea, Egypt

Inaki Relanzon / Rothschild giraffe (Giraffa camelopardalis rothschildi) grazing on Acacia tree, Nakuru Lake National Park, Kenya, August, Critically endangered

Guy Edwardes / Blue tit (Parus caeruleus) perched, Dorset, England February

Hanne & Jens Eriksen / Graceful prinia {Prinia gracilis} perched on twig, Dhofar, Oman

Nick Garbutt / Adult Wagler's pit / Temple viper (Tropidolaemus wagleri) in thorns on the stemless Asam Paya Palm (Eleiodoxa conferta) Bako NP, Sarawak, Borneo, Malaysia.

Jouan & Rius / Thorny devil (Moloch horridus) Central Australia

Mary McDonald / Grey-headed Kingfisher {Halcyon leucocephala} flying from an Acacia tree in Samburu NR, Kenya.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) feeding on coral. Komodo, Indonesia.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) and Blue starfish (Linckia laevigata) on coral reef. Komodo, Indonesia.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) feeding on coral. Komodo, Indonesia.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) feeding on coral. Komodo, Indonesia.

GEORGETTE DOUWMA / Crown of thorns starfish (Acanthaster planci) feeding on coral, Komodo, Indonesia

GEORGETTE DOUWMA / Crown of thorns starfish (Acanthaster planci) crawling over sandy area between reefs, Komodo, Indonesia

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) feeding on coral, Komodo, Indonesia

Jouan & Rius / Tree trunk covered with spines, typical of dry forest, Guanacaste, Costa Rica

Jouan & Rius / Camel thorn pods {Vachellia erioloba} Kalahari desert, South Africa

Martin Gabriel / Camelthorn thorns {Acacia erioloba} half buried in sand, Namib desert, Namibia

Rolf Nussbaumer / Common Tree Frog {Hyla arborea} adult resting in wild rose bush, National Park Lake Neusiedl, Austria, April

George Chan / Close-up of desert plants in the Junggar Basin, Xinjiang Province, North-west China. September 2006

Niall Benvie / Welted thistle {Carduus acanthoides} flowers, Scotland

Juergen Freund / Snorkler collecting Crown of thorns starfish {Acathaster planci} Underwater Indo-Pacific

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) on coral reef, Red Sea, Egypt.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) feeding on coral, Red Sea, Egypt.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) on coral reef, Red Sea, Egypt.

GEORGETTE DOUWMA / Crown-of-Thorns cardinal fish (Siphamia fuscolineata) sheltering amongst spines of Crown-of-Thorns starfish {Acanthaster planci}, commensalism, Great Barrier Reef, Australia.

GEORGETTE DOUWMA / Crown-of-Thorns cardinal fish (Siphamia fuscolineata) sheltering amongst spines of Crown-of-Thorns starfish {Acanthaster planci}, commensalism, Great Barrier Reef, Australia.

GEORGETTE DOUWMA / Crown-of-thorns starfish (Acanthaster planci) on coral reef, Egypt, Red Sea.

David Welling / Cultivated rose reflected in water droplets on rose stem with thorns

Chris Gomersall / Linnet (Carduelis cannabina) adult female perched on bramble carrying nest material. Fowlmere RSPB reserve, Cambridgeshire. April.

Rob Tilley / Agave (Agave genus), Phoenix Botanical Gardens, Arizona, USA. April 2006

Rob Tilley / Saguaro cactus flower (Carnegiea gigantea) detail with fly, against blue sky. Sonora Desert Museum, Tucson, Arizona. April 2006

Rob Tilley / Agave (Agave genus) close-up, Desert Botanical Museum, Phoenix, Arizona

Steven David Miller / Green anole {Anolis carolinensis} brown phase, on thorny stem. SW Florida, USA

Jeff Rotman / Crown-of-thorns Starfish (Acanthaster planci), close-up of spines. Egypt, Red Sea.

Jeff Rotman / Crown-of-Thorns Starfish (Acanthaster planci) mouth and feet. Egypt, Red Sea.

Jeff Rotman / Crown-of-Thorns Starfish (Acanthaster planci) feeding on coral at night. Egypt, Red Sea.

Philippe Clement / Desert spiny lizard (Sceloporus magister) climbing Ocotillo (Fouquieria splendens). Saguaro National Park, Arizona, USA