Wildlife TV

Learn interesting and funny plant and animal facts with videos and photos

Mating for Life Part 4: Why are Animals Monogamous?

  • Why are animals monogamous?

As we’ve seen in previous posts (about birds, mammals and insects), monogamy is common in some parts of the animal kingdom and rare in others, but the way in which it is practised varies a great deal. But what are the advantages of being faithful to a mating partner? Generally speaking, it makes sense for animals to be promiscuous; mating with a lot of partners increases the chance of producing a large number of offspring as well as increasing the chance of having the opportunity to mate with the most desirable partner. However, monogamy does have some advantages, as demonstrated by many of the species we have already discussed.

Warthog Family

Warthogs (Phacochoerus africanus) are promiscuous animals; the males wander around large areas, mating with any females they come across. They sacrifice selectivity for increased chances of producing young every breeding season. Photo Credits.

Monogamy does have its advantages: Many animals, such as Azara’s night monkey males (Aotus azarae) invest a huge amount of time and energy into raising their young and so they are motivated to minimise the risk of accidentally raising another male’s offspring; they do this by having a system of mating for life and staying faithful to their partners, ensuring that their chosen female will birth only his offspring. Some animals practice ‘mate guarding‘ in order to secure reproductive success; once a male has mated with a female, he stands guard over her to ensure that no other males will also mate with her. This may not entirely qualify as monogamy, however, it may explain why partners stay together for at least as long the gestation period (until the offspring is born).

Many animals spend a lot of time and energy acquiring mates; performing elaborate displays and courtship rituals. This behaviour ensures that animals select the best mates possible (strongest, fastest, most agile etc.), it makes sense for animals to stick with their partner once they have been selected so that the process does not have to be repeated; they have a reliable partner who can provide offspring without having to waste time and energy each mating season. This is best exemplified by albatrosses (family: Diomedeidae) who invest the first 10 – 15 years of their life practicing and then attempting to secure mates; once they get one, they stick with them for life.

Black Browed Albatross (Thalassarche melanophrys)

Albatrosses, such as these black-browed albatross (Thalassarche melanophrys), mate for life, eliminating the need to perform mating rituals every breeding season. Photo Credits.

One significant advantage of mating for life, or at least being monogamous for a significant period of time is that young animals can have both parents around in their early life to help raise them. This system of rearing young is efficient as parents can take turns finding food while the other stays behind to protect the infant(s) and is best demonstrated by the emperor penguin (Aptenodytes forsteri) where parents take turns doing a 200km round trip to get food from the sea and return to the inland colony in Antarctica.

Emperor Penguin Family

Emperor penguins (Aptenodytes forsteri) are serially monogamous meaning they form very close social bonds with their partners, but pick new ones each breeding season. Photo Credits.

There have been many studies that have attempted to demonstrate and explain the origins of monogamy in animals. It has been suggested that infanticide (the killing of youngsters) caused the development of monogamy. In some species, such as lions (Panthera leo), when a male takes control over a group of females from another male, he will kill all of his predecessor’s cubs so that the females will become sexually receptive once again. Monogamy counteracts this by evolving a system where males will stay with their females long-term in order to ensure that their offspring grow up to independence successfully.

African Lions (Panthera leo)

Male lions (Panthera leo) practice infanticide; when taking over a new pride (group) they will kill the offspring of their predecessor to make the females receptive to mating again. Photo Credits.

There is also evidence that hormones can contribute to monogamy. A chemical called oxytocin is found in mammals (including humans (Homo sapiens)) and seems to be released into the body during moments such as child birth, copulation and suckling. Oxytocin might be released in animals’ bodies to promote proximity and bonding between individuals. In humans, it’s the chemical that makes you feel good when thinking about people you love.

As always, the animal kingdom is full of complexity and fascinating behaviour. Although most animals do not show faithful monogamy to a partner, the ones that do have some very good reasons to do so. I hope you enjoyed this series and learned something along the way!

Much love,

-Nick

1 Comment »

How do Scorpions Mate?

In the previous post we started looking at the mating behaviours of arachnids. Arachnids are a group of invertebrates that are identified as having 8 legs. Most people know that spiders are arachnids but the group also includes ticks, mites, solifuges and scorpions. It is the mating techniques of the scorpions which we will look at in this entry.

Scorpions (Order: Scorpiones) have quite an intimate mating technique. Males and females will spend quite some time attempting to locate one another using sensory organs underneath their bodies called pectines. They will trace each other’s pheremone trails and upon meeting, they begin their intimate courtship with the pair locking pincers together, and sometimes also their mouth parts (chelicerae). The two will then ‘dance’ together, moving around in circles on the ground until the male finds a suitable surface where he can deposit his sperm; he then has to lead her in the dance in order to position her over the sperm so that she can receive it using her pectines. This mating technique is so romantic it even has a French name, the Promenade à Deux.

An image of an Opistophthalmus scorpion displaying its large pincers.

Although a scorpion’s pincers can be used as deadly weapons, they are also tools for intimate courtship rituals.
Photo Credits.

We’ve seen in the previous entry and in this one that the arachnid world can be gross and brutal but there are moments that we can relate to. It’s never a good idea anthropomorphising animal behaviour, but it is humorous to draw comparisons between how arachnids practice their mating behaviour to humans; males providing dinner for females showing off with dancing prowess, even massages. The difference being that human females are somewhat unlikely to kill and devour the male!

I hope you’ve enjoyed learning about the mating behaviour of spiders and scorpions.

Coming soon is a series of articles on how many animals will mate for life, starting with birds. Find out even more animals’ mating techniques on our series page.

Much love,

-Nick

Leave a comment »

How do Hippopotamus mate?

Last time in this series on mating techniques, we learned how porcupines can overcome some physical obstacles in order to achieve the act of mating and thus producing offspring. Porcupines of course are covered in sharp quills which makes copulation difficult, in this article we will look at another animal that might be considered to have some difficulty dealing with the physical logistics of mating.

Hippopotamuses

When it comes to the hippo (Hippopotamus amphibious), similarly to the porcupine, the physical act of copulation seems to be impractical; they appear to be unwieldy, gigantic creatures so how does the male manage to clamber on top of the female in order to copulate?

Hippos are aquatic mammals and spend the vast majority of their time in the water; they are quite closely related to whales and dolphins but have not entirely committed to fully aquatic lifestyle, still making use of legs when they come out of the water at night to graze and mark territory. But aside from the few hours each night in which hippos get out and about, all of the rest of their activity takes place in the river, lake, dam or wherever they live, and hippo mating behaviour, as an activity, is no exception.

So how do hippos mate? Well, when underwater, hippos are quite buoyant which is helpful because, surprisingly, they can’t even swim! But being able to float helps the male get on top of the female efficiently without the need for any gymnastics or threats to her safety. However, mating is not by any means a sweet and loving process for hippos; males can be as much as double the weight of females and frequently end up holding their partners underwater, during the act the females often struggle to get free to reach the surface to take a breath. Males in general are also quite aggressive and will fight with deadly force to prevent other males from having access to the females they have acquired in their social group.

A gargantuan male hippo (Hippopotamus amphibius) mounts a smaller female, using his buoyancy in the water to assist him.

A huge male hippo (Hippopotamus amphibius) mounts a smaller female, using his buoyancy in the water to assist him.
The Red-Billed Oxpeckers (Buphagus erythrorhynchus) on his back don’t seem to feel like giving the couple any privacy!
Photo Credit.

If mating has been successful then a baby hippo will be born about 8 months later and, as you might have guessed, the birthing takes place underwater, so the calf, immediately from birth, will have to swim to the surface before it can even take its first breath.. So, as you can see, right from the start of their lives, they are inexorably linked to the water, it protects them and allows them to reproduce despite their physical ‘limitations’.

I hope you enjoyed learning how hippopotamus mate.

Do you would also like to learn how porcupines mate?

Check out our “Series” page for the list of “Mating Techniques“.

 -Nick

 

Leave a comment »