Alex Mustard,Alex Mustard / Whaleshark (Rhincodon typus) swimming and filtering fish eggs from the water. A behaviour known as ram-feeding. Isla Mujeres, Quintana Roo, Yucatan Peninsular, Mexico. Caribbean Sea.

Patricio Robles Gil / Bighorn sheep (Ovis canadensis) ram grazing in snow, Wind River Range, Wyoming, USA, January

Sebastian Kennerknecht / Bighorn Sheep (Ovis canadensis) ram browsing in winter, Lamar Valley, Yellowstone National Park, Wyoming

Alex Mustard / Whale shark (Rhincodon typus) ram feeding in very shallow, plankton rich waters of La Paz bay. La Paz, Baja California Sur, Mexico. Sea of Cortez, Gulf of California, East Pacific Ocean.

Connor Stefanison / Rocky mountain bighorn sheep (Ovis canadensis) ram eating grass, Jasper National Park, Alberta, Canada. December.

Will Watson / Welsh Mule ewe, crossbred sheep for prime meat production from a Bluefaced Leicester ram, with two new born lambs suckling in a pen, Herefordshire, England. April

Brent Stephenson / Soay sheep (Ovis aries) ram feeding amongst flowering bluebells (Hyacinthoides non-scripta). Lundy, Devon, United Kingdom. May.

Brent Stephenson / Soay sheep (Ovis aries) ram feeding amongst flowering bluebells (Hyacinthoides non-scripta). Lundy, Devon, United Kingdom. May.

Brent Stephenson / Soay sheep (Ovis aries) ram feeding amongst flowering bluebells (Hyacinthoides non-scripta). Lundy, Devon, United Kingdom. May.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaque (Macaca fascicularis aurea) using stone tools to open Oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaque (Macaca fascicularis aurea) on beach feeding on cockles cracked opened using stone tools at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) on beach using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) on beach using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) on beach using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) feeding on cockles opened using stone tools at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaque (Macaca fascicularis aurea) feeding on cockles opened using stone tools at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Tourists feeding Burmese long tailed macaques (Macaca fascicularis aurea), Kho Ram, Khao Sam Roi Yot National Park, Thailand, October 2013.

Mark MacEwen / Burmese long tailed macaque (Macaca fascicularis aurea) using stone tools to open Oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open cockles at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaques (Macaca fascicularis aurea) using stone tools to open Oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaque (Macaca fascicularis aurea) feeding on cockles opened with stone tools at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Burmese long tailed macaque (Macaca fascicularis aurea) using stone tools to open Oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

Mark MacEwen / Adult male Burmese long tailed macaque (Macaca fascicularis aurea) using stone tool to open oysters at low tide, Kho Ram, Khao Sam Roi Yot National Park, Thailand.

George Sanker / Mature bighorn (Ovis canadensis) ram feeding in a high mountain pass in Jasper National Park, Alberta, Canada, September

George Sanker / Mature bighorn (Ovis canadensis) ram feeding in a high mountain pass. Jasper National Park, Alberta, Canada, September

Lou Coetzer / Nile crocodile (Crocodylus niloticus) with mouth clasped round young Impala (Aepyceros melampus) ram for more than 2 hours after taking it, Chobe River, Botswana, May.

Donald M. Jones / Bighorn Sheep (Ovis canadensis) ram grazing on plants in snow, northern Rocky Mountains, Canada

Yva Momatiuk & John Eastcott / Dall's Sheep (Ovis dalli) sub-adult ram nibbling on Dwarf Willow (Salix herbacea), Denali National Park, Alaska

Daniel Heuclin / Ouessant sheep (Ovis aries) head portrait of Ram grazing, France

Daniel Heuclin / Ouessant sheep (Ovis aries) head portrait of Ram grazing, France

Patricio Robles Gil / Dall sheep (Ovis dalli) ram feeding, Denali National Park, Alaska, USA

Patricio Robles Gil / Dall sheep (Ovis dalli) ram feeding, Denali National Park, Alaska, USA

Patricio Robles Gil / Dall sheep (Ovis dalli) ram feeding, Denali National Park, Alaska, USA

Patricio Robles Gil / Bighorn sheep (Ovis canadensis) ram with ewes feeding in snow, Wild River Range, Wyoming, USA, January

Sumio Harada / Bighorn Sheep (Ovis canadensis) rams digging through snow to feed, Glacier National Park, Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams feeding during winter in Jasper National Park, Canada

Yva Momatiuk & John Eastcott / Dall's Sheep (Ovis dalli) rams feeding together on golden willow leaves, Denali National Park, Alaska

George Sanker / Close-up of Bighorn sheep (Ovis canadensis) ram grazing, Jasper National Park, Rocky Mountains, Alberta, Canada, Autumn

Sebastian Kennerknecht / Bighorn Sheep (Ovis canadensis) ram browsing, Glacier National Park, Montana

Sebastian Kennerknecht / Bighorn Sheep (Ovis canadensis) ram grazing, Glacier National Park, Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams grazing, Jasper National Park, Canada

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams grazing, Jasper National Park, Canada

Mark Raycroft / Bighorn Sheep (Ovis canadensis) portrait of a ram feeding

Sumio Harada / Bighorn Sheep (Ovis canadensis) male feeding on snowy ground, Glacier National Park, Montana

Thomas Mangelsen / Timber Wolf (Canis lupus) feeding on Dall's Sheep (Ovis dalli) in river, Denali National Park and Preserve, Alaska

Sebastian Kennerknecht / Bighorn Sheep (Ovis canadensis) rams browsing in winter, Lamar Valley, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / Bighorn Sheep (Ovis canadensis) ram browsing in winter, Lamar Valley, Yellowstone National Park, Wyoming

Sebastian Kennerknecht / Bighorn Sheep (Ovis canadensis) ram browsing in winter, Lamar Valley, Yellowstone National Park, Wyoming

Donald M. Jones / Dall's Sheep (Ovis dalli) rams feeding on Quaking Aspen (Populus tremuloides), Yukon, Canada

Donald M. Jones / Bighorn Sheep (Ovis canadensis) young ram eating Spotted Knapweed (Centaurea maculosa), Montana

Donald M. Jones / Bighorn Sheep (Ovis canadensis) rams grazing on plants in snow, northern Rocky Mountains, Canada

Martin Gabriel / Male sheep / ram, Extremadura, Spain

Dawn Y. Wilson / Bighorn Sheep (Ovis canadensis) ram feeding on grass, Shoshone Canyon, Wyoming

Kristel Richard / Mouflon (Ovis aries musimon) herd, male alert whilst females graze at woodland edge. Rewilding project, Beremytske Nature Reserve, Chernihiv Region, Ukraine. February.