Pheromones in the Animal World
Whether the goal is to mate, control the female’s reproductive cycles, affect gestation and onset of puberty, aggressively defend a nest, lay a territorial boundary, send a warning signal, estab...
Whether the goal is to mate, control the female’s reproductive cycles, affect gestation and onset of puberty, aggressively defend a nest, lay a territorial boundary, send a warning signal, establish a relationship of dominance/submissiveness, identify members of one’s family, or act in a maternal manner toward offspring, pheromones are the key components of the chemical communications that drive animal behavior.
How and where these pheromones are produced and released varies greatly from creature to creature. For example, the single-celled amoeba Dicgzostelium discoideum produces a pheromone, acrasin, that attracts others of its kind. Hamsters and other rodents have pheromones in their vaginal secretions. Female hamsters produce and release the strong pheromone apbrodisin, which stirs up sexual interest and behavior in the male. Dogs, horses, deer, camels, and a number of other graziing ungulates also have concentrated levels of pheromones in l their urine. So powerful are canine pheromones that a bitch in heat can lure males from miles away with her pheromones. Pigs, we have just learned, load up their saliva with pheromones. Learn about pheromones and the vomeronasal organ (VNO).
Some animals produce pheromones in specialized glands located in the genital and anal areas of their bodies and in the sebaceous glands of their skin. Throughout history, the odiferous substances secreted by these glands in the musk deer, civet cat, beaver, and muskrat have been sought after and used in perfumes (the evolution of perfume is discussed in chapter 7). In some species of insects, specialized “message” glands exist solely to produce pheromones. For example, the male cockroach has a gland on its abdomen that secretes a pheromone designed to incite mating behavior in the opposite sex.
Like humans, other mammals and reptiles possess a vomeronasal organ that processes pheromone signals. The location of y the VNO varies among species, but most often it is near the oral or nasal cavity. (Most insects carry their pheromone receptors on the delicate branches of their antennae.) Mammals, amphibians and reptiles all possess olfactory and accessory olfactory systems}.
Pig Breath and Other Animal Wonders
If she doesn’t get a hug or a cuddle afterward, no worry. Upon completing the sex act, the sow and the boar (in all of our references, a boar is an uncastrated male pig) have accomplished their goal: propagation of the species.Pheromones also explain the strange attraction of pigs to trufes. Researchers at the Technical University of Munich and die Liibeck School of Medicine were curious about why a sow will root passionately for hours in search of a single trufe. They unearthed an amazing fact: Trufes send out a chemical come-hither that is identical to 5-alpha-androstenol. Trufes produce even greater quantities of the chemical than do pigs. No wonder the poor, confused female trufe pig cannot help but follow her nose to the source. As Carl Sagan and Ann Druyan wrote in Shadows of Forgotten Ancestors, “Since truffles are fungi, in which steroids play key sexual roles, perhaps tormenting sows is just an accidental side-effect—or perhaps it serves the function of inciting pigs to dig so the spores are spread more widely and the Earth is covered with truffles.”
Hog farmers have capitalized on the fact that the sow is highly receptive to the pheromones in the male pig’s saliva and breath. “Boar Mate” is used by farmers to coax female pigs into lordosis without putting an actual male in front of them. This makes artificial insemination more effective and profitable: one spray of the stuff and the sow is smitten.
Pigs provide but one example of how nonhuman animals use pheromonesto communicate. The topic of animal pheromones has been researched extensively; we address it briey in these pages, but the notes at the end of the book contain sources for readers who wish to learn more.
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ABOUT THE AUTHOR
Alexander P is a blogger who studies pheromones.