We meet some of the animals that mate for life, but are monogamous relationships in animals as sweet as they seem?

By Leoma Williams

Published: Saturday, 11 November 2023 at 21:20 PM


Although the idea of life-long pairings is appealing, with sweet pairs of animals mating for life and raising families together, as a mating strategy monogamy is actually very rare in the natural world.

Mating for life only arises in situations where it will improve reproductive success, such as when male as well as female parental care is vital for the survival of offspring. This is why it is so much more common in birds than in other animal groups, as chicks are very small and vulnerable, and as they are incubated outside the body, males are given the chance to pitch in.

Birds such as penguins, swans, and albatrosses are thus often the first that people go to when thinking of animals that mate for life. 

As you will find out, however, even lifelong monogamy in animals doesn’t always equate to sexual exclusivity. Just like humans animals not only break up – “divorcing” after a failed breeding attempt for example –  they also have affairs. Genetic analysis has revealed surprises about many previously assumed very “faithful” animals.

Like an animal version of Jeremy Kyle, paternity does not always match up with living arrangements! Read on to find out more.

Learn about ten more things you never knew about animal sex.

What animals mate for life?

Black Vultures (Coragyps atratus)

© Getty Images

It seems fitting to begin our list with a bird, as they are the group of animals that show by far the highest level of monogamous mating. Over 90% of bird species form some kind of monogamous pair bond, although this may not be lifelong, and they are not always “faithful”.

Black vultures have a particularly strong monogamous bond, however, staying with their chosen mates all year round and for multiple breeding seasons. Unlike many other bird species, they appear to be very loyal to their mate, with genetic evidence showing that they do not seem to have so-called “extra-pair copulations”. The partnership is sealed with a courtship ritual that involves strutting and head-bobbing.

Shingleback skink (Tiliqua rugosa)

© Getty Images

In contrast, the next on our list of animals that mate for life is from a group in which a monogamous reproductive style is extremely rare. In lizards, polygamy (males mating with multiple females) and polyandry (females mating with multiple males) are much more common.

In these skinks however social monogamy – wherein they pair bond and associate with the same long-term partner for many years – is the norm. These relationships have been known to persist for up to 20 years. Social monogamy does not necessarily imply strict sexual monogamy, however, and refers more to living patterns.

Although socially monogamous species may live and raise young together, they do sometimes mate outside this pair, with one study finding that about 20% of the males in their sample mated with more than one female. This social but not strict sexual monogamy is something that these lizards share with others on our list.

Eursian beaver (Castor fiber)

The Eurasian beaver on the other hand is a particularly faithful mate. These rodents live in family groups consisting of a male and female and their offspring. In this case their social monogamy does seem to correspond with sexual monogamy, with young only belonging to bonded pairs.

This is in contrast to North American beavers (Canada’s national animal) in which genetic analysis has found that as much of 50% of litters are sired by more than one male, indicating that unlike their Eurasian cousins these female beavers are having sneaky affairs.

Prairie vole (Microtus ochrogaster)