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For better or worse …

By Jonathon Howard

Can animals be married? According to the dictionary marriage is a ‘legally or formally recognized union of two people as partners in a personal relationship’. There is no such thing as ‘legal recognition’ for animals, but we can recognise when two individuals have close lifelong partnerships.

Shingleback lizards (Tiliqua rugosa) sometimes referred to as ‘stumpy-tails’ or ‘faithful lizards’, are the only known monogamous reptile species in the world. They live for up to 50 years. During that time, they acquire long-term partners and stay in close proximity by using scent trails.

During the spring breeding season, the male will often follow immediately behind her and waits while she feeds. He sacrifices eating, to serve as lookout should danger threaten.

Such monogamy is rare in reptiles, but it is more common in birds: particularly sea birds. For example, black-browed albatrosses form monogamous pairs that can last for their entire 70-year lifespan.

Every year, after wandering far and wide across the ocean, these albatrosses will return to the same partner, perform their same secret dance, and start nesting.

Such loyalty does not occur across all bird species. The reason why a bond may only be short lies in the average lifespan of the species in question. Albatrosses and shinglebacks live for many years. Whereas the blue wrens that live in your backyard live for less than 6 years.

It seems that if you are a blue wren and choose to mate for life when the likelihood of your partner goes missing is high, then you might waste important breeding opportunities looking for a partner that may no longer be alive. However, if you only have 6 years to live why not take any opportunity when the mating season starts?

This may explain why fairywrens are socially monogamous and sexually promiscuous. Both males and females will regularly mate with other individuals. What’s more the young are often raised not by the pair alone. Other individuals will help.

For socially monogamous species, divorce tends to be a strategy only used to correct for sub-optimal partnerships. Returning back to our example of the albatross, climate change is causing oceans to warm. The result is less food and lower reproductive success for breeding albatrosses.  And in what is both a sad and bizarre twist of fate, scientists are now finding higher rates of divorce in these birds. Environmentally driven divorce may therefore represent an overlooked consequence of global climate change.