Photos: Animal Tracks: Aug. 4  - Aug. 11

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  1. Chimp off the old block

    Shiba, a chimpanzee at Sydney's Taronga Zoo, holds her newborn baby on Aug. 10. (Lisa Ridley / AFP - Getty Images) Back to slideshow navigation
  2. Cow caress

    Emma Leis lays on a cow at the Wisconsin State Fair in West Allis, Wisconsin, on Aug. 9. (Jim Young / Reuters) Back to slideshow navigation
  3. When pigs flee

    Pigs race at the Wisconsin State Fair in West Allis, Wisconsin, on Aug. 9. (Jim Young / Reuters) Back to slideshow navigation
  4. Dog takes catnap

    A 29-day-old Labrador puppy sleeps against a tree at a courtyard in Beijing on Aug. 10. (Jason Lee / Reuters) Back to slideshow navigation
  5. Busy bee

    A bee gathers nectar along Skyline Drive in Shenadoah National Park in Virginia on Aug. 9. (Karen Bleier / AFP - Getty Images) Back to slideshow navigation
  6. Bright butterfly

    An eastern tiger swallowtail butterfly flies in Shenadoah National Park in Virginia on Aug. 9. (Karen Bleier / AFP - Getty Images) Back to slideshow navigation
  7. Seeing double

    A gorilla is reflected in a window at the Hellabrunn Zoo in Munich, Germany, on Aug. 8. (Sven Hoppe / AFP - Getty Images) Back to slideshow navigation
  8. Blooming plumage

    A peacock displays his plumage at the Hellabrunn Zoo in Munich, Germany, on Aug. 8. (Sven Hoppe / AFP - Getty Images) Back to slideshow navigation
  9. Rock on

    A 9-month-old baby samang, a tailless, black-furred gibbon native to forests in Malaysia and Indonesia's Sumatra province, holds onto a rock during a Hindu ritual ceremony in Bali, Indonesia, on Aug. 9. (Firdia Lisnawati / AP) Back to slideshow navigation
  10. Sitting pretty

    Parrots look around at the ZOOM zoo in Gelsenkirchen, Germany, on Aug. 8. (Patrik Stollarz / AFP - Getty Images) Back to slideshow navigation
  11. Meerly looking

    A meerkat stands and watches visitors at the ZOOM zoo in Gelsenkirchen, Germany, on Aug. 8. (Patrik Stollarz / AFP - Getty Images) Back to slideshow navigation
  12. At the end of their rope

    Pig-tailed macaques climb on a rope at the ZOOM zoo in Gelsenkirchen, Germany, on Aug. 8. (Patrik Stollarz / AFP - Getty Images) Back to slideshow navigation
  13. The eyes have it

    A snow owl at the ZOOM Zoo in Gelsenkirchen, Germany, on Aug. 8. (Patrik Stollarz / AFP - Getty Images) Back to slideshow navigation
  14. On the prowl with a growl

    A tiger walks around at the ZOOM zoo in Gelsenkirchen, Germany, on Aug. 8. (Patrik Stollarz / AFP - Getty Images) Back to slideshow navigation
  15. Big bad wolf

    Chingiz, a male Siberian forest wolf, walks around inside an open-air cage at the Royev Ruchey Zoo in Russia on Aug. 8. (Ilya Naymushin / Reuters) Back to slideshow navigation
  16. Washing up

    Masha, a female raccoon, holds a piece of cloth in a pan with water, placed by zoo employees, at the Royev Ruchey Zoo in Russia on Aug. 8. (Ilya Naymushin / Reuters) Back to slideshow navigation
  17. Teeny turtle

    A zoo worker holds a newborn river terrapin on display at Dusit Zoo in Bangkok on Aug. 8. The River Terrapin is one of the most critically endangered turtle species. (Pornchai Kittiwongsakul / AFP - Getty Images) Back to slideshow navigation
  18. Lengthy lick

    A giraffe licks its face at the Philadelphia Zoo on Aug. 7. (Michael Zorn / Getty Images) Back to slideshow navigation
  19. National bird

    An American bald eagle surveys its surroundings at the Philadelphia Zoo on Aug. 7. (Michael Zorn / Getty Images) Back to slideshow navigation
  20. Silly seal

    A young seal emerges from the water in Friedrichskoog, Germany, on Aug. 7. (Daniel Bockwoldt / DPA via AFP - Getty Images) Back to slideshow navigation
  21. Leaving the hospital

    Crowds of beach goers watch Mitchell, a 65-pound juvenile loggerhead sea turtle, crawl back to the ocean during the release of rehabilitated sea turtles on Aug. 6 in Isle of Palms, South Carolina. The turtle which accidentally swallowed a fishing hook and had it surgically removed by the sea turtle hospital at the South Carolina Aquarium in Charleston. (Richard Ellis / Getty Images) Back to slideshow navigation
  22. Pampered pachyderms

    An elephant keeper sprinkles coconut oil on orphaned elephants at the David Sheldrick Elephant Orphanage within Nairobi National Park in Kenya on Aug. 6. (Thomas Mukoya / Reuters) Back to slideshow navigation
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By
updated 11/16/2006 3:39:08 AM ET 2006-11-16T08:39:08

When it comes to mating, wild animals make their own rules. From lionesses of East Africa that mate with many males before ovulating and committing their eggs, to male walruses that joust for several female partners, the animal kingdom is full of swingers.

In some human societies, sexual behavior akin to these animals would be shunned. Do these animals just not care what "society" thinks about their promiscuous behavior? Even the most domestic of animals, dogs, don't bat an eye before sniffing a fellow canine's butt or humping an owner's leg.

"Just about every animal is quite promiscuous," said Diana Fisher, a behavioral ecologist at the Australian National University.

Though such free animal love might appear lighthearted, survival and passing on genes are serious business in the animal world.

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Animal "personal ads" would reveal a conflict between males and females. Males want to mate with as many females as possible with the goal of fertilizing the most eggs. Females are a little more selective, preferring to hook up with the best males to fertilize their eggs.

One end result is polygyny — the most common mating strategy in the animal kingdom — in which males compete for access to a harem of breeding females. Sexual selection tends to favor adaptations that enhance reproductive success, including a large body size to boost success in pre-mating combat between males, and high sperm counts to up the chances of successful fertilization.

Rather than investing limited resources in inflating their bodies, females typically have a more conservative growth strategy and allocate more into the production and provisioning of offspring. By waiting on the sidelines during male-male jousting, the female can mate with the strongest male.

"Males fight it out and the best fighters get large harems of females," Tim Clutton-Brock, an animal ecologist at the University of Cambridge, told LiveScience. "If you just take the winner, you've got the best male. You don't need to sit back and choose carefully between males."

Human males must decide how much energy to put into weightlifting, for instance, to woo women, and how much they should focus on a career, which would benefit a family.

For polygynous horned beetles, the same trade-off exists between allocating resources to developing mate-winning weaponry in the form of horns and having more sperm to increase fertilization. In one study, when researchers cut off the beetles' horns, the pupa reacted by developing larger testes, supporting a theory known as resource allocation trade-off.

Females in charge
For females, the drawbacks of sex with lots of partners include an increased probability of inbreeding, higher chances of predation, more risk of catching disease and physical injury or exhaustion from the frequent sex.

Even so, in some species, females "wear the pants." Called polyandry, by mating with multiple males, a mom can produce healthier offspring, and in some species, ensure devotion and help in child-raising by many fathers.

In a study of a mouselike marsupial, scientists found that by sleeping around, females had a better chance of finding males with good-quality sperm and high sperm counts [video]. "So that means that females that mate with lots of males get more of their offspring sired by the good-quality males that increase the baby survival," Fisher told LiveScience, referring to the mouselike marsupials.

In a lab study, researchers found that female guppies mating with four different males gave birth to 73 percent more young than their monogamous sisters. Plus, the young were more skilled at swimming in tandem with another fish and jetting out of trouble.

But strict polyandry, where one female guards a group of male mates, is rare. "The benefit for the female is quite clear, because if you have four husbands and you lay them each a clutch of eggs and they sit on it, you're doing much better than if you have one husband and you lay one clutch of eggs," Clutton-Brock said.  "What's harder to explain is what the benefit to the male is."

Deciding factors
As with humans, animal mating often relies on a careful dance in which males and females develop ways of getting what they want without going too far and ending up empty handed.

The female Australian hanging fly will allow males that provide larger nuptial gifts to copulate longer, and in turn transfer more sperm, skewing paternity. Males providing insufficient gifts get flung off by the female before insemination is complete.

A study of 14 water-strider species found that species in which males had flat stomachs and powerful forelimbs for clutching lovers mated more frequently than species where females were in charge — those with spines protruding from their back ends. When the females had the upper hand, mating occurred about twice a day compared with 20 times a day in the male-dominating species.

Find out how 10 animals have developed polygamous behaviors, many of which will cause a blush or two, in this LiveScience special: Top 10 Swingers of the Animal Kingdom.

© 2012 LiveScience.com. All rights reserved.

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