Howler monkey's selection
This is an extraordinarily serious issue for the Howler monkeys. They need to consider if they want to use the limited resources on howling - competition against the other males in the tribe for land - or generating sperm - conquering every female they come across.
First, let's take a look at the characteristics of the howling monkey:
- The bigger the hyoid bone, the less number of monkeys in the mating group.
- The bigger the hyoid bone, the smaller the testicle - and fewer sperms produced.
Therefore, howler monkeys need to make their choice among the two options. This seemingly contradictory phenomenon is actually reasonable, because there are two types of mating systems in the social organization of these monkeys.
- Harem exclusive mating mode: this is made up of a small group, usually with only one strong male who monopolizes the mating rights of several females; therefore, it doesn’t need to produce more sperms. The frequent mating with the females ensures the male plenty of offspring, and all he need to do is to howl loudly.
- Group inclusive mating mode: this is a large group of birds, with as many as 5 or 6 males. The females will mate with all the males within the group, and males do not have exclusive rights to a certain female. This leads competition on the number and the quality of sperms. Hence male howling birds with smaller hyoid bones will have larger testicles.
Those with both a small hyoid bone and testicle are - due to natural selection - dying out or will die out. Natural selection is ruthless, and the weak will not be able to pass down their genes.
The tactics employed by the monkeys before and after mating and the physical differences present among the monkeys are parts of the balance of evolution. It is incredibly common in the natural world that an individual does not have all the competitive advantage In species with a strict one male mate with one female rule, the competition for sperm is little to none.
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The wrongly accused lovebirds
There's an old saying that goes: "envy the happiness of a pair of mandarin ducks rather than the immortal celestial beings -- nothing can be better than being together with one's love.” This expression has long been a symbol of romantic love; however, Mandarin ducks are not monogamous. The lovers are only together during the spring mating season. Throughout the reproductive period mandarin ducks will live together and raise their hatchlings. But once reproduction is over, the young couple will immediately go separate and find new mates. Not only that, but even during the reproductive period, mandarin ducks will occasionally seek out another mate.
Ironically, mandarin ducks have been a symbol of faithful love since ancient times, because they always come and go in pairs;some even believe that mandarin ducks are martyred after the death of their spouses. The obvious error is that people cannot make sure they are meeting the same pair of mandarin ducks everytime they see two of them walking together. Studies, however, have found that a mandarin duck does not mate with the same partner every year during the estrus.
How can we tell the difference between male and female mandarin ducks? Here are a few tips:
- Feel the cloaca: The cloaca of male mandarin ducks has a small spacing between the pubic bones, and shows a protrusion. The cloaca of female mandarin ducks has a large spacing between the two bones, especially in adult female mandarin ducks. There's no protrusions in the female's cloaca. A middle finger can be reached in through out the spacing.
- The male mandarin ducks have a thin body, tight hair; they are usually aggressive and have small eyes. The female mandarin ducks have a fat body, fluffy hair, big eyes that are closer to the top of their head. They are also relatively less active.
- Look at their standing posture: The male mandarin ducks will stand tall and show their strength. The female Mandarin ducks usually stand in a prone position, showing their meekness.
- Look at the tip of their tail feathers: the tip of the tail feathers of male mandarin ducks is sharp, while the tip of the tail feathers of female mandarin ducks is divided into a W shape.
- Look at the shape of their heads: male mandarin ducks have relatively small, pointed heads. l. Female mandarin ducks have flat, round heads,slightly larger compared to those of males.
That is all about introduction to mandarin ducks. They not only have more than one partner in their life, but also do not stay single after their partner's death. These are just stereotypes people created for mandarin ducks.
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The pursuit of love with the gardener's bird
Many species of animals will put in a lot of effort to find a mate, but very few birds will have as elaborate of a mating process as the bowerbird. They will build a structure similar to a bird nest, and will add decorations on to it to attract the attention of the opposite sex. Additionally, they will tour the structure other birds have built to evaluate the attractiveness of the nests and the “proposers” . Male bowerbirds like to use bright blue to decorate their nests. They will also find many shiny decorations to create a sharp contrast of colors.
If the female bowerbird fancy this “artwork”, she will enter the nest. The male bowerbird will then dance around with a shiny decoration in its beak. Bowerbirds are not only master architects, but also artists. Some male birds even use flower petals and man-made glitter to decorate their nests.
Citation：
(2023, March 31). 【冷知识】吼猴叫得越响，睾丸越小-千篇网. 千篇网. https://qianp.com/knowledge/44297.html
Costandi, M. (2012, January 19). Male bowerbirds use visual illusions to enhance their mating success. The Guardian. http://www.theguardian.com/science/neurophilosophy/2012/jan/19/1
鸳鸯是一夫一妻制吗？如何分辨公母？ - 惠农网. (n.d.). 鸳鸯是一夫一妻制吗？如何分辨公母？ - 惠农网. https://news.cnhnb.com/rdzx/detail/445705/
自然界中，哪些动物是终身一夫一妻制？_鸳鸯. (2020, December 27). 自然界中，哪些动物是终身一夫一妻制？_鸳鸯. https://www.sohu.com/a/440168726_221039
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