Have you ever heard of the surprising bonding between dogs, cats, birds and other animals? Yes, it's true that animals make the most unlikely friendships on earth that will leave us wondering, "Even we can't get along like that".

In her book titled "Unlikely Friendship", Jennifer Holland tells a heartwarming tale of animals which bond in the most unexpected ways. Holland, a National Geographic magazine writer, documented 47 remarkable stories of animals that have nothing in common but share a strong sense of kinship unlike any other.

Over the years, animal lovers have captured amazing and unforeseen moments of the bizarre friendships that exist in the animal world.  

Here are a couple of snapshots, from a cat caring for a mouse to a chimpanzee feeding milk to a 60-day-old tiger cub, that define friendship in its own way:

Unlikely Friendship
A Belington Terrier (L) and a Pomeranian Spitz look at each other during the International Dog Show in Afula October 9, 2010.(Reuters)
Unlikely Friendship
Mohammad Al-Hamoury holds a kitten and a puppy (R) at his house in Amman February 26, 2009. Al-Hamoury's cat Smaigel is parenting four puppies whose mother died in a car accident. Source: Reuters
Unlikely Friendship
One-year-old white tiger Bombay plays with 4 year-old Dalmatian Jack at the Circus William in Berlin October 25, 2008. The two animals live peacefully together in the same enclosure for a few months. Source: Reuters
Unlikely Friendship
Keow Wan, a four-month-old Sun Conure parrot, perches on Yim, a dog whose name means smile in Thai, as their owners take part in a pray for peace ceremony at Royal Plaza in Bangkok October 22, 2008. The owners dressed up the dog and the parrot and put the two together to bring joy and happiness to all who see the pair. Source: Reuters
Unlikely Friendship
A Bengal tiger and cougar cubs sit with a german shepherd at a veterinarian's house in Sydney April 2, 2001. Source: Reuters
Unlikely Friendship
Auan, a seven-year-old female cat, licks the body of Jeena, a three-year-old male mouse, at a farmer's house in the central province of Phichit, 450 km (281 miles) north of Bangkok on August 7, 2002. The animals owners say Auan found Jeena three years ago and has been his playmate and protector, including warding off dogs, since then. Source: Reuters
Unlikely Friendship
A monkey helps a parrot get rid of lice at a wild animal park in Shenzhen, south China's Guangdong province, in this picture taken on April 23, 2005. The character on the monkey's hat reads "Buddha". Picture taken on April 23, 2005. Source: Reuters
Unlikely Friendship
A dog feeds two tiger cubs in a zoo in Hefei, east China's Anhui province in this picture taken on May 2, 2005. The tigers mother, who gave birth to the two cubs on May 1 is unable to produce enough milk and the zoo keepers found a dog to act as the wet nurse. Source: Reuters
Unlikely Friendship
Two-year-old chimpanzee "Do Do" feeds milk to "Aorn", a 60-day-old tiger cub, at Samut Prakan Crocodile Farm and Zoo in Samut Prakan province on the outskirts of Bangkok July 30, 2011. The crocodile farm, used as a tourist attraction, houses some 80,000 crocodiles and is the largest in Thailand. Source: Reuters
Unlikely Friendship
A monkey does a handstand on the head of a sheep during a performance at a temple fair held to celebrate the upcoming Chinese New Year in Beijing February 13, 2010. Source: Reuters
Unlikely Friendship
Morphy, a 45-day-old dog, and Cathey, a 30-day-old cat, play at a veterinary hospital as they wait to be vaccinated in the southern Indian city of Hyderabad July 6, 2007.Source: Reuters
Unlikely Friendship
Nimra, a one-year-old cat, plays with chicks in Amman May 13, 2007. Nimra has been taking care of seven chicks after their mother's death a month ago. Source: Reuters
Unlikely Friendship
A tiger cub climbs over piglets at a park in Guangzhou, south China's Guangdong March 13, 2007. The tiger cub was abandoned by its mother and is being raised by a sow. Picture taken March 13, 2007. Source: Reuters