Humans aren't the most faithful species around. When it comes to fidelity, I think animals can pull it off better. Here are eight species who only mate with a single partner in a lifetime, hence are termed monogamous species.
Swans can form monogamous pairs that often last for many years, up to a lifetime. Two swans swimming close to each other, forming a shape of a heart with their necks - which has become a universal love symbol.
2. Turtle Doves
Turtle doves are migratory species, smaller in build than other doves. They are distinguishable from their wedge-shaped tail, with white borders; especially when they fly away from you.
"turtle" comes from the Latin turtur as the dove makes a deep vibrating "turr..turr.." sound upon it's arrival in spring. Nothing to do with the reptile - turtle!
Turtle doves form very strong pair bonds, and thus the reason why, in the song The Twelve Days of Christmas, Turtle doves come in pairs of two!
Populations of turtle doves are falling rapidly due to changes in farming practices (as they feed on weed seeds) as well as shooting practices in Mediterranean countries.
These huge birds can travel over great distances, but despite all that, it will always return to the same place and the same partner during the breeding season. The monogamic pairs can form bonds with each other that will last a lifetime; usually through affectionate ritual dances.
4. Bald Eagles
The national emblem of the United States. These birds will only have a partner for an entire life, unless in an event of death of either one.
5. Black Vultures
Inner beauty or good looks? Black vultures show us looks aren't key in a faithful relationship. In fact, they attack other vultures that are caught philandering or rather, having extra-marital affairs!
Wolves often have a much more loyal and faithful familial relationship than us. As such, wolf packs usually contain the two parents, and their offsprings! Amazing isn't it...
Gibbons, a family of the Lesser Apes, express very low sexual dimorphism, meaning both the male and female are of almost equal size. Also, this means they are on equal footing in terms of relationships.
8. Schistosoma Mansoni Worms (Schistosoma japonicum)
These parasitic worms often cause the disease known as schistosomiasis or snail fever (snail fever, because freshwater snails carry this parasite!). The reproduce sexually in humans, and they stick together for life. hmm.. this is sick, but they stick together via a groove in the male, which the female resides.
The parasite can penetrate the human skin into post-capillary venules, where they travel to lungs and other parts of the body. It's chronic and normally gotten from swimming in infected waters.