.png)
https://ift.tt/2hVTgDc
Male dominance is frequently assumed to be the norm in the animal kingdom and has been a significant matter of reform in modern human society. Yet other species, some well-known and others obscure, with extremely intricate social arrangements or perplexing life histories may astound us with their incredible characteristics of female domination within the species. We take a tour of some highly gender role biased species where the female takes the upper hand, sometimes putting males at a disadvantage, and sometimes simply being the greater predator or literally the sole bloodthirsty one out of the two genders in a species.
10. Topi Antelope
Male ungulates are notorious for their chaotic and sometimes crazed pursuit of the female, but the female Topi antelope of sub-Saharan Africa puts the shoe on the other foot as she hounds males for sexual encounters in the mating season. Fights break out between the females as they seek their preferred male while in estrus, which lasts only one day per year, making the competition urgent and sometimes fierce. Though females have taken control of the mating game in this species, the preferred males for which they compete are males which are the most dominant, assertive and capable themselves. Females may choose males with which they have mated in the past and will also take their dominant behavior to the next level by breaking up matings between rival females and desired males.
A study from the University of Jyväskylä, Finland and the Institute of Zoology, London noted that the short breeding times coupled with repeated pressure from females to mate with the most desirable, territory males also lead males to become choosy about which females they accept for mating. The result is a strange reversal of roles where males may spurn the advances of the pushiest females, instead choosing to save their sperm for those with whom they have not mated. Topi are among the fastest of antelope, with a running speed that may top out at around 50 miles per hour.
9. Naked Mole Rat
Living underground like grubs, the bizarre, subterranean hairless rodent known as the Naked Mole Rat exists in colonies governed by a dominant queen in a fashion comparable to a bee or termite. Native to hot, inhospitable grasslands in Ethopia, Somalia and Kenya, Naked Mole Rats forage in intricate underground tunnels and possess thick, translucent skin and sharp, elongated incisors. Female mole rats draw upon remarkable adaptations to maintain dominance in the insect-like colony. The queen is the only breeding female in the colony, preventing all other females from breeding through her aggressive dominance and social role enforcement, which frequently consists of physically shoving other colony members.
The queen only mates with several chosen males, which become heavier than non-breeding males. Special spinal adaptations allow the spine of the female mole rat to extend as she becomes longer and heavier than even the breeding males, growing larger than the rest of the colony like a queen termite. Breeding females may weigh 53 grams, while workers weigh as little as 32 grams. Incredibly, the dominance of the queen is reflected biochemically throughout the colony to a remarkable degree. Breeding male testosterone levels alternate in sync with the hormonal fluctuations of the female, non-breeding male testosterone levels are constantly low, while the ovary development and hormones of all other females are suppressed. If removed from the colony, however, surprised sexual characteristics and hormones bounce back.
8. Phalaropes
A colorful and peculiar shorebird, the three species of phalarope are shorebirds that have evolved webbed feet to swim in deep water and are known for their curious reversal of the gender roles typically associated with birds. In a remarkable display of avian female dominance, phalarope hens have the upper hand in size, beauty and social structure. Females of the three phalarope species are far more colorful than the drab males and larger, hinting at their absolute dominance. Notorious for keeping what amounts to a harem of males, phalarope hens pursue desired males, fighting with rival females to gain access to the mates they want.
The phalarope mating season consists of them mating with several males and placing the responsibility of incubating the clutch of four eggs and raising the young completely at the feet of each male selected as a mate. Having completed their transfer of responsibilities to a number of males, possibly as many as four, the females are free to forage and migrate while letting the males worry about reproduction. Wilson’s Phalaropes, exclusive to the Americas, are birds of inland freshwater environments, while the other two species, the circumpolar Red-necked Phalarope and Red Phalarope, inhabit coastal and open ocean waters throughout the non-breeding season.
7. Birds of Prey
Featured prominently in the heraldry of many nations, that impressive eagle, falcon or goshawk gracing a coat of arms is best considered to be a female if it looks large and powerful. In an unusual example of reverse sexual dimorphism, male birds of prey may be a little bit smaller or even puny compared to females, depending on their ecology. In species where prey is easy to catch, such as eagles, mammal-eating buteo hawks and Old World vultures, females are marginally larger than the males. Conversely, the females of species who hunt more elusive fare may dwarf the males. Female accipiters such as the goshawks, which feed on other avian species and bird eating falcons may see a vast difference in mass between male and female, as great as 50 percent.
The difference in size has sparked speculation among biologists, with early theories suggesting female bulk wards off male aggression. Yet, that theory has not held up well under further investigation. Current theories suggest that the difference reduces competition between the male and female by diverting them into hunts for differently sized prey and increasing total prey captured to feed the young. Furthermore, smaller prey are more abundant and easier to find but require agility to catch. Males have more time to hunt than nesting females and may have evolved a smaller build to capture abundant but agile prey, while the larger build of the female may assist in incubation. Of course, this allows her to take down larger and more impressive and dangerous prey than the males when she hunts.
6. Octopus
Mating may seem enjoyable for some species, but male octopuses face the challenge of mating with powerful and aggressive females that frequently opt to consume the male for extra nourishment after gaining the sperm from the male. Octopus sexual cannibalism means males must leap through many hoops to both mate and survive, including jumping on the female from the rear and then making an escape. In species where females frequently eat males, longer mating arms have evolved to maintain a safe distance while impregnating hungry females. Sexual cannibalism is so characteristic of octopuses that a Panamanian researcher’s 1982 discovery of benign cohabitation and beak to beak, repeat mating in the Larger Pacific Striped Octopus was ignored until being discovered to be true 30 years later.
In addition to cannibalism, sheer dimorphism among octopus sexes can be extraordinary in favor of the female. In the most extreme example, that of the open ocean going argonauts, or paper nautiluses, males are under 1 inch in length, whereas females reach nearly 4 inches in length in an extraordinary case of sexual dimorphism. Physical mating between female argonaut and quarter sized male does not actually take place. Instead, the male releases a specially adapted tentacle known as the hectocotylus, which swims off on its own and delivers the sperm into the giant female. Upon fertilization, the female secretes material building a huge calcareous shell used as an egg case, which partially fills with air and creates the appearance of a nautilus or extinct ammonite.
5. Mosquito
We may associate the male animal with aggression and predation, yet in what are among the most banal yet not commonly understood natural enemies of mankind, the mosquitos, only females are the blood sucking agents of attack. Not actually bugs but instead a member of the thread-horns, a group of long-bodied flies, mosquitos, whose name means “Little Fly” in Spanish, have a well-earned bad reputation among humans. Technically known as ectoparasites as a result of their unpleasant and sometimes deadly, disease vectoring behavior, female mosquitos have a very specific reason for attacking live prey in search of blood.
The reason for the gender separation between vampire and non-vampire in mosquitos actually has to do with the great nutritional value of blood in equipping the female to reproduce. Male mosquitos do not harvest blood, but instead feed on plant juices like nectar to obtain sugar. Females feed on plant juices as well, but require blood as a means to gain protein to make eggs. Having obtained a rich soup of proteins, amino acids and blood cell constituents, female mosquitos are well equipped to transform their gain into a healthy batch of eggs. And those eggs will hatch into aquatic mosquito larvae, which give back to the ecosystem as an important element of the aquatic food web, while adult mosquitos feed many birds.
4. Orca
Not actually a whale, but the world’s most powerful and deadly dolphin species, the Killer Whale or Orca patrols the oceans for prey in wolf-pack like groups called pods. It might come as a surprise that Orca pods are led by matriarchal females who make an immense contribution to the knowledge economy that defines orca survival. With their complex cultural, behavioral and information networks, orca require familiarity with the environment and expert guidance to track their food across vast distances and rear their young.
According to findings published in Current Biology, female orcas stop bearing young at around 40 years of age but can live 90 years. In those latter years, female orcas that have exceeded 35 years of age are more likely to lead the pack than either younger females or male orcas. At the same time, leadership by older females increased in frequency in years that the salmon supply was short in the Puget Sound study area. While the implications of the research are subject to debate, the findings suggest that the presence of older female leaders provides valuable assistance in finding prey and delivering environmental and ecological knowledge to the pod as they hunt. A 2012 study indicated that the presence of older female orcas increased the survival rates of young whales in the pod, noting that orcas have the longest post-reproductive lifespan in the animal kingdom, excluding humans.
3. Spotted Hyena
The most powerful bite of all mammals is that of the Spotted Hyena, and in this species, the female is the larger, stronger, and dominant gender. Characteristic of sub-Saharan Africa, the Spotted Hyena is the largest hyena species and an accomplished hunter that will even eat the bones after a successful kill. Related more closely to felines than the dog family it so closely resembles, the Spotted Hyena is also a dramatic example of female dominance in a mammal species. Significant physical and social structure based adaptations position female Spotted Hyenas as high-ranking ladies in their groups, known as clans.
With as many as 100 hyenas in a clan, social groupings are run by dominant females in a gender defined society tilted so strongly in favor of the females that even an adult male newcomer ranks below cubs belonging even to a low ranking female. Yet, it is the physiology of the female Spotted Hyena that that is most shocking. The clitoris of the female spotted Hyena is greatly elongated and has evolved into a “pseudopenis” that looks almost exactly like the penis of a male mammal. In fact, the female’s genitalia is capable of erection and possesses penile spines. Unique among all female mammals in lacking an external vaginal opening, the female Spotted Hyena remarkably urinates, copulates and gives birth through this pseudopenis.
2. Praying Mantis
Prized as a hunter of garden pests and kept as a pet or subject of scientific fascination, the praying mantises are alien-like in appearance with an equally unearthly breeding system. By allowing females to eat them as prey after mating, certain male praying mantis species, such as the Chinese Mantis, contribute to the reproductive capability of the female. Female fecundity is increased when the size of prey taken is increased and evidently, a male mantis serves as a useful source of large prey. A study published by the Royal Society B found that 63 percent of the diet of the female Chinese Mantis during the breeding season may consist of sexually cannibalized males.
Investigation revealed that egg production rates in the female Chinese Mantis increased by 50 eggs for each male cannibalized after mating, creating a pure reproductive advantage for the female. The situation seems to be an entirely losing proposition for the male, but in fact it is often not. Mating opportunities for males vary in frequency and when the chance of encountering another female is low, below 20 percent, the male mantis actually gains through the ability to father 50.9 more offspring in the case of the Chinese mantis if he lets himself be consumed. Radioisotope tests clearly showed how the male leaves a legacy of amino acids and other nutrients in the form of extra eggs and female reproductive tissue nourishment once consumed.
1. Dwarf Mongoose
Admired for their ability to bring down snakes, members of the mongoose family are well liked carnivores with a weasel-like appearance. One of the smallest members of the mongoose family, the Dwarf Mongoose sub-Saharan Africa is also known for organizing into female run social groups of around 12-15 members with some rather surprising rules and regulations. The smallest native carnivore of the African continent, the Pygmy Mongoose groups are headed up by an alpha female who holds the sole breeding rights among all of the females in her colony.
Other females are not permitted to breed, but may assist in raising the young born to the dominant female mongoose. If other females do in fact breed, their young may be killed, maintaining the social hierarchy. The dwarf mongoose social structure does accommodate the role of alpha male, appointed as a guard in charge of territorial defense and acting as a sentinel. However, his role is a rank below that of the alpha female who oversees all. Despite their diminutive build, the Dwarf Mongoose colony may occupy a territory up to 75 acres in size from which they glean a wide diversity of prey, from birds and insects to snakes and lizards.
AMAZING
TRENDS,AMAZING
via Toptenz.net http://www.toptenz.net
May 14, 2018 at 05:30AM
No comments:
Post a Comment