Dave Watts / Eastern grey kangaroo (Macropus giganteus) with joey in pouch, Australian Capital Territory, Australia, September

Michael Pitts / Saltwater crocodile underwater {Crocodylus porosus} Kakadu NP, NT, Australia

Alex Mustard / Two female Common seahorses (Hippocampus kuda) fighting over territory on the seabed. The brief fight was preceeded by a ritualised, synchronised parade. Bitung, North Sulawesi, Indonesia. Lembeh Stra...

Steven David Miller / A Perentie (Varanus giganteus) using its forked tongue to detect smells, Alice Springs Reptile Centre, Northern Territory, Australia, Captive. May.

Marie Read / Wood Ducks (Aix sponsa), females behave aggressively toward a male (second from right) that is trying to join them on a floating log, autumn, New York, USA, October.

Marie Read / Canada geese (Branta canadensis) two during territorial fight in early spring, Ithaca. New York, USA

Marie Read / American avocets (Recurvirostra americana) two during aggressive (territorial) encounter, Bear River Migratory Bird Refuge, Utah, USA, May.

Matthew Maran / Red Fox (Vulpes Vulpes) patrolling the allotment North London, England, UK, September.

Steven David Miller / Red-collared lorikeet (Trichoglossus rubritorquis) pair examining hole in Eucalyptus as a potential nesting hollow. Katherine, Northern Territory, Australia.

Dave Bevan / Male Pied flycatcher (Ficedula hypoleuca) calling to establish territory and attract a mate, Carmarthenshire, Wales, UK, May.

Giri Cavale / Melanistic leopard / Black panther (Panthera pardus) on territorial patrol on track, Nagarahole National Park, Nilgiri Biosphere Reserve, Karnataka, India.

Paul Williams / Budgerigars (Melopsittacus undulatus) flocking to find water, Northern Territory, Australia