8:00:00 AM
The dogs nose – olfactory sense or nose-ability
Coren says, “[f]or a dog, his nose not only dominates his face, it also dominates his brain…thus his picture of the world.” An interesting point Coren makes is that certain mammals such as “humans, apes, monkeys and birds” rely more on visual cues to assess their environment and other mammals such as the dog rely more on scent. According to Coren, the dog’s brain is designed to access information more from scents and works differently from the human brain that is more reliant on “vision and light-related data” (Coren, 2004).
Comparing the size of the human and dog brain we find the dog’s is “one-tenth” the size. Comparing the area of the dog’s and human’s brain known as the olfactory bulbs, where scent is assimilated we find the dogs is “four times larger” than a humans. In addition to this remarkable characteristic, dogs have an increased ability to detect and identify even minute amounts of scent. For example, a rather well know fact regarding the dog’s ability to detect “butyric acid” a component of sweat “is from 1 million to 100 million times better” than ours.
The anatomy of the nose
The exterior portion, known as the leather is the dog’s nose. The color, usually dark can be brown, pink or spotted sometimes depending on the breed. The pattern visible if you look closely is “believed to be as individual and unique as a human’s fingerprints.” It has actually provided positive identification in some documented instances and “noseprint registries” actually exist. In addition, the dog has the ability to move independently both nostrils enabling him to detect the direction of scents. In order to obtain scents from their environment the dog actually closes down his normal breathing process in order to take in scents (Coren, 2004).
The nostrils lead to the nasal cavity comprised of a “bony shelflike structure” that traps the air containing the odor. Here the odors accumulate and are interpreted. Eventually the air containing the scent reaches a “set of scroll shaped, bony plates called ‘turbinates’.” The turbinates allow contact with the “collected odor and the olfactory mucosa.” The olfactory mucosa contains “cilia” which are described as “hairlike dendritic elaborations of the olfactory receptor neuron” (Lindsay, 2000).
The information received from these “receptor cells” is processed and sent to the olfactory bulbs and then passed onto the brain for further analysis. The scenting ability is breed dependent, with longer muzzled dogs having a greater amount of odor gathering surface thus increasing their scenting ability. In comparison, the entire area “…containing these odor analyzers is about one square inch” in humans and the dogs entire area may be as much as “60 square inches” (Coren, 2004).
It is important to understand this difference in breeds when selecting an odor detection dog. Not only the increased surface area of receptor cells enhances a dog’s ability, but also through selective breeding, those dogs with long floppy ears have distinct advantage. The long floppy ears like the Blood Hound or Bassett Hound enable more scent directed to their nose. According to Coren, when the dog moves their ears push “…the air down to the ground and helps lift the scent back up to their nose.” So if you are looking for a good tracking candidate, look to the length of the ears (Coren, 2004).
The Vomeronasal Organ
The vomeronasal organ occurs in many mammalian species, but whether it is functional is not clear in humans and some primates. This organ is located in the roof of the dog’s mouth just behind the incisors with an opening into the mouth. The organ lined with cells is similar to those found in the olfactory mucosa, but instead of cilia, we find “microvilli”. The information received through this organ passes through this “accessory olfactory bulb” and goes directly to the limbic system. The vomeronasal organ is specialized in the detection of “pheromone molecules” and according to Lindsay, “[t]his difference makes the VNO more sensitive for the detection of nonvolatile chemical messages deposited in the urine and other bodily secretions” (Lindsay, 2000).
“[T]he detection and subcortical analysis of …sexual pheromones” according to Lindsay serves an important function. Loss of sexual activity occurs when the VNO ceases to function and has causal effects on “maternal care, aggressiveness, and secretion of sex hormones” in mammals (Lindsay, 2000).
An interesting behavior associated with the VNO is “tonguing” and considered a similar response to the “flehmen response” found in felids and some other mammals. Describing this response in dogs, one would observe the dog pushing his tongue rapidly against the roof of its mouth. In addition, you might observe teeth chattering and foam collected on the upper lip. This behavior is likely observed after licking a urine spot, tasting of the air or “…following the exchange of mutual threat displays between two rival males”, according to Lindsay. Additionally, you might observe a slight tongue extrusion, with a wide lip retraction and a slight elevation of the muzzle accompanied “…by several brief sniffs and wide searching side to side” of the head (Lindsay, 2000).
In spite of contrary evidence to the existence of a “flehmen response” and the VNO in dogs, there are those who disagree. “Overall (1997) suggested that the vomeronasal complex lacks functionality altogether, noting that the vomeronasal sacs are without chemoreceptors.” To the contrary, other scientist disagree saying “…the VNO system may be less well developed in dogs than in some other animals…it is a functional organ of some importance to dogs.” However, we do not fully understand it function, but suspect it is responsible for receiving pheromone information regarding the social status and reproductive states of conspecifics and other mammals (Lindsay, 2000).
An important discovery concerning the VNO and it’s functionality concerns a study of wolves reaction to a chemical known as methyl p-hydroxybenzoate, which is a sexual pheromone. According to Lindsay, Klinghammer known for his wolf program and studies found “…captive wolf subordinates may court and mount an estrous female without interference from the alpha male” however when this chemical is detected the alpha wolf will actively defend “…his rights of exclusivity.” It appears this chemical “…coincides with ovulation and standing heat.” Interestingly, this chemical is found in the “…estrous secretions” of female dogs and is considered to be responsible for sexual arousal and male mounting behavior, even when applied to neutered female dogs genital area (Lindsay, 2000).
Similar to humans dogs come equipped with apocrine glands that are responsible for information about age, sex, health and emotional state. In humans, these glands are located in specific areas such as the armpits and groin area. In dogs and other mammals these glands found over the entire body, give these animals more body odor in comparison to that of a human. The concentrated pheromones found in the dog’s hair help provide easy identification of other dogs.
Dog’s urine and fecal matter contain pheromones and provide dogs with a lot of information. Dogs prefer to mark on vertical surfaces to allow the transference of the scent through the air. The height can indicate the size, which could indicate dominance. According to Coren, “dominance” is more important to male dogs, thus lifting the leg allows higher urination marking and prevents smaller dogs from marking over.
The emotional state and urine
The emotional state of animals can be determined by the “…release of a set of stress-related hormones” found in most body fluids such as tears, urine, sweat and blood. For dogs, the ability to detect certain hormones could influence their survival. Coren says what we think as “the scent of fear” may indicate “the scent of danger” to a dogs’ companions and the absence of this scent indicates safety and possibly the acceptance to make social contact (Coren, 2004).
When dogs meet with conspecifics they tend to prefer spending most of their time sniffing the anal genital areas where the odors are more concentrated. This information helps determine social interaction. According to Coren, even dogs living in the same household will sniff each other to determine moods and any advance warning of aggression.
The crotch hound
Most is not all of us have been the recipient of a dog sniffing our crotch and the embarrassment it usually brings. Dogs are equally attracted to the groin area of humans as much as their own conspecifics because we both have the same apocrine sweat glands and they become especially interested when there is scent related to sexual behavior. Recent sexual behavior, women during menstrual cycles and those recently giving birth will be of special interest to dogs. Dogs used in studies to predict ovulation in cows are considered more reliable than conventional methods. Coren even suggests that we could use dogs as a predictor for birth control, giving the family dog a new duty.
Discrimination between scents
An incredible ability of the dog is the ability to discriminate scent among same species. The “…concept that canines evolved the ability to pick out the scent of one individual animal, even though his track has been crossed, re-crossed, and trampled over by a whole herd of animals of the same species” is an incredible feat according to Coren. Humans can detect the difference between scents, but not when covered over by a stronger smell (Coren, 2004).
Dogs differ from humans in this ability. Humans are able to separate objects according to visual cues and canines are able through scents. Dogs have the ability to separate scents, breaking them down and concentrating on individual scents. Without this ability, dogs would not be able to perform the different working tasks related to this ability.
Offensive smells
Those scents containing citrus and spicy smells are considered offensive to canines and have prompted the use of citronella in “no bark” collars and often used to deter dogs from forbidden areas. However, once the dog acclimates to this odor, it loses its effectiveness. This creates deterrents for smugglers of illegal contraband disguised among lemons or limes for instance.
Human detection
When we compare a dogs ability to discriminate between human scent and a humans ability to identify another human using our better visual acuity, dogs have a much better ability and are correct in nearly “80 percent of the time” according to Coren (Coren, 2004).
According to Coren, most research on the humans’ ability to identify a criminal suspect is usually in the form of a police lineup. Understanding humans rely more on visual cues and dogs more on scent, psychologist have determined that humans are only reliable in correctly identifying suspects in only “55 percent” of the cases (Coren, 2004).
It seems that mistakes in identifying suspects has led researchers to suspect that dogs have the ability to not only recognize and identify individual scents, but can discriminate from what body part the scent originated. Therefore, when a dog is unable to identify a specific scent, it might indicate the scent object taken from a crime scene does not match the test object. According to Coren, “[t]he better a dog gets to know a person, or the more scent samples he gets from different regions of the body and taken at different times, the more likely the dog will begin to learn the specific basic scent that discriminates one person from another” (Coren, 2004).
What researchers have discovered is “[d]ogs are most likely to confuse members of the same family” living together and confused by identical twins, but could benefit if both twins ate different diets and the dog was allowed to obtain scent from each, prompting the dog to detect those subtle differences necessary to distinguish one from the other.
Still another way dogs assist humans in tasks such as tracking is facilitated by body particles known as ‘rafts’ or ‘scurf’ that researches believe are “…tiny bits of skin cells” that are actually part of the scent. These tiny bits of skin are covered in sweat and bacteria and are shed from the human body at a rate of “…500 million cells” per minute falling like a “…shower of microscopic snowflakes” making it easy for dogs to stay on an individual scent trail (Coren, 2004).
Similar to the dogs’ ability to detect the distance of sound, the dog uses the difference between the intensity of the scent measured between the steps. The previous steps will be weaker with the more recent steps providing clues necessary to keep them on track. In addition, weather plays a significant role in preservation of scent trails, with warm days and ultraviolet light making it difficult but not impossible. However, dogs have other clues that are helpful including soil and grass that may be disturbed and these odors mixed with the scent of the quarry are still detectable by dogs. These clues are not subject to weather conditions but are if repeatedly walked over by other humans.
How Dogs Use Their Noses
There are three ways dogs use their noses in working environments through tracking, trailing and air sniffing. This ability is breed specific and the individual breed determining which method works best. Tracking is described as the most reliable method, with the dog following his quarry with nose down and relying on disturbed vegetation to assist. Trailing, best described as, relying on loose skin cells more than foot prints and depending on wind direction may affect the specific path putting the dog slightly off direction, but still able to detect his quarry.
Air scenting is an alternative to these previous methods and is greatly dependent on weather conditions. This method is more suited to disaster search and rescue efforts when location is more important that using a trail. Dogs more suitable to this task are the German shepherd dog and Labrador retriever.
Humans have discovered many ways to utilize the dogs scenting abilities, including police work, search and rescue, assistance dogs for impaired individuals, detection of chemicals, certain accelerants, bacteria, molds, and termites and most recently detecting human medical conditions.
Coren says, “[f]or a dog, his nose not only dominates his face, it also dominates his brain…thus his picture of the world.” An interesting point Coren makes is that certain mammals such as “humans, apes, monkeys and birds” rely more on visual cues to assess their environment and other mammals such as the dog rely more on scent. According to Coren, the dog’s brain is designed to access information more from scents and works differently from the human brain that is more reliant on “vision and light-related data” (Coren, 2004).
Comparing the size of the human and dog brain we find the dog’s is “one-tenth” the size. Comparing the area of the dog’s and human’s brain known as the olfactory bulbs, where scent is assimilated we find the dogs is “four times larger” than a humans. In addition to this remarkable characteristic, dogs have an increased ability to detect and identify even minute amounts of scent. For example, a rather well know fact regarding the dog’s ability to detect “butyric acid” a component of sweat “is from 1 million to 100 million times better” than ours.
The anatomy of the nose
The exterior portion, known as the leather is the dog’s nose. The color, usually dark can be brown, pink or spotted sometimes depending on the breed. The pattern visible if you look closely is “believed to be as individual and unique as a human’s fingerprints.” It has actually provided positive identification in some documented instances and “noseprint registries” actually exist. In addition, the dog has the ability to move independently both nostrils enabling him to detect the direction of scents. In order to obtain scents from their environment the dog actually closes down his normal breathing process in order to take in scents (Coren, 2004).
The nostrils lead to the nasal cavity comprised of a “bony shelflike structure” that traps the air containing the odor. Here the odors accumulate and are interpreted. Eventually the air containing the scent reaches a “set of scroll shaped, bony plates called ‘turbinates’.” The turbinates allow contact with the “collected odor and the olfactory mucosa.” The olfactory mucosa contains “cilia” which are described as “hairlike dendritic elaborations of the olfactory receptor neuron” (Lindsay, 2000).
The information received from these “receptor cells” is processed and sent to the olfactory bulbs and then passed onto the brain for further analysis. The scenting ability is breed dependent, with longer muzzled dogs having a greater amount of odor gathering surface thus increasing their scenting ability. In comparison, the entire area “…containing these odor analyzers is about one square inch” in humans and the dogs entire area may be as much as “60 square inches” (Coren, 2004).
It is important to understand this difference in breeds when selecting an odor detection dog. Not only the increased surface area of receptor cells enhances a dog’s ability, but also through selective breeding, those dogs with long floppy ears have distinct advantage. The long floppy ears like the Blood Hound or Bassett Hound enable more scent directed to their nose. According to Coren, when the dog moves their ears push “…the air down to the ground and helps lift the scent back up to their nose.” So if you are looking for a good tracking candidate, look to the length of the ears (Coren, 2004).
The Vomeronasal Organ
The vomeronasal organ occurs in many mammalian species, but whether it is functional is not clear in humans and some primates. This organ is located in the roof of the dog’s mouth just behind the incisors with an opening into the mouth. The organ lined with cells is similar to those found in the olfactory mucosa, but instead of cilia, we find “microvilli”. The information received through this organ passes through this “accessory olfactory bulb” and goes directly to the limbic system. The vomeronasal organ is specialized in the detection of “pheromone molecules” and according to Lindsay, “[t]his difference makes the VNO more sensitive for the detection of nonvolatile chemical messages deposited in the urine and other bodily secretions” (Lindsay, 2000).
“[T]he detection and subcortical analysis of …sexual pheromones” according to Lindsay serves an important function. Loss of sexual activity occurs when the VNO ceases to function and has causal effects on “maternal care, aggressiveness, and secretion of sex hormones” in mammals (Lindsay, 2000).
An interesting behavior associated with the VNO is “tonguing” and considered a similar response to the “flehmen response” found in felids and some other mammals. Describing this response in dogs, one would observe the dog pushing his tongue rapidly against the roof of its mouth. In addition, you might observe teeth chattering and foam collected on the upper lip. This behavior is likely observed after licking a urine spot, tasting of the air or “…following the exchange of mutual threat displays between two rival males”, according to Lindsay. Additionally, you might observe a slight tongue extrusion, with a wide lip retraction and a slight elevation of the muzzle accompanied “…by several brief sniffs and wide searching side to side” of the head (Lindsay, 2000).
In spite of contrary evidence to the existence of a “flehmen response” and the VNO in dogs, there are those who disagree. “Overall (1997) suggested that the vomeronasal complex lacks functionality altogether, noting that the vomeronasal sacs are without chemoreceptors.” To the contrary, other scientist disagree saying “…the VNO system may be less well developed in dogs than in some other animals…it is a functional organ of some importance to dogs.” However, we do not fully understand it function, but suspect it is responsible for receiving pheromone information regarding the social status and reproductive states of conspecifics and other mammals (Lindsay, 2000).
An important discovery concerning the VNO and it’s functionality concerns a study of wolves reaction to a chemical known as methyl p-hydroxybenzoate, which is a sexual pheromone. According to Lindsay, Klinghammer known for his wolf program and studies found “…captive wolf subordinates may court and mount an estrous female without interference from the alpha male” however when this chemical is detected the alpha wolf will actively defend “…his rights of exclusivity.” It appears this chemical “…coincides with ovulation and standing heat.” Interestingly, this chemical is found in the “…estrous secretions” of female dogs and is considered to be responsible for sexual arousal and male mounting behavior, even when applied to neutered female dogs genital area (Lindsay, 2000).
Similar to humans dogs come equipped with apocrine glands that are responsible for information about age, sex, health and emotional state. In humans, these glands are located in specific areas such as the armpits and groin area. In dogs and other mammals these glands found over the entire body, give these animals more body odor in comparison to that of a human. The concentrated pheromones found in the dog’s hair help provide easy identification of other dogs.
Dog’s urine and fecal matter contain pheromones and provide dogs with a lot of information. Dogs prefer to mark on vertical surfaces to allow the transference of the scent through the air. The height can indicate the size, which could indicate dominance. According to Coren, “dominance” is more important to male dogs, thus lifting the leg allows higher urination marking and prevents smaller dogs from marking over.
The emotional state and urine
The emotional state of animals can be determined by the “…release of a set of stress-related hormones” found in most body fluids such as tears, urine, sweat and blood. For dogs, the ability to detect certain hormones could influence their survival. Coren says what we think as “the scent of fear” may indicate “the scent of danger” to a dogs’ companions and the absence of this scent indicates safety and possibly the acceptance to make social contact (Coren, 2004).
When dogs meet with conspecifics they tend to prefer spending most of their time sniffing the anal genital areas where the odors are more concentrated. This information helps determine social interaction. According to Coren, even dogs living in the same household will sniff each other to determine moods and any advance warning of aggression.
The crotch hound
Most is not all of us have been the recipient of a dog sniffing our crotch and the embarrassment it usually brings. Dogs are equally attracted to the groin area of humans as much as their own conspecifics because we both have the same apocrine sweat glands and they become especially interested when there is scent related to sexual behavior. Recent sexual behavior, women during menstrual cycles and those recently giving birth will be of special interest to dogs. Dogs used in studies to predict ovulation in cows are considered more reliable than conventional methods. Coren even suggests that we could use dogs as a predictor for birth control, giving the family dog a new duty.
Discrimination between scents
An incredible ability of the dog is the ability to discriminate scent among same species. The “…concept that canines evolved the ability to pick out the scent of one individual animal, even though his track has been crossed, re-crossed, and trampled over by a whole herd of animals of the same species” is an incredible feat according to Coren. Humans can detect the difference between scents, but not when covered over by a stronger smell (Coren, 2004).
Dogs differ from humans in this ability. Humans are able to separate objects according to visual cues and canines are able through scents. Dogs have the ability to separate scents, breaking them down and concentrating on individual scents. Without this ability, dogs would not be able to perform the different working tasks related to this ability.
Offensive smells
Those scents containing citrus and spicy smells are considered offensive to canines and have prompted the use of citronella in “no bark” collars and often used to deter dogs from forbidden areas. However, once the dog acclimates to this odor, it loses its effectiveness. This creates deterrents for smugglers of illegal contraband disguised among lemons or limes for instance.
Human detection
When we compare a dogs ability to discriminate between human scent and a humans ability to identify another human using our better visual acuity, dogs have a much better ability and are correct in nearly “80 percent of the time” according to Coren (Coren, 2004).
According to Coren, most research on the humans’ ability to identify a criminal suspect is usually in the form of a police lineup. Understanding humans rely more on visual cues and dogs more on scent, psychologist have determined that humans are only reliable in correctly identifying suspects in only “55 percent” of the cases (Coren, 2004).
It seems that mistakes in identifying suspects has led researchers to suspect that dogs have the ability to not only recognize and identify individual scents, but can discriminate from what body part the scent originated. Therefore, when a dog is unable to identify a specific scent, it might indicate the scent object taken from a crime scene does not match the test object. According to Coren, “[t]he better a dog gets to know a person, or the more scent samples he gets from different regions of the body and taken at different times, the more likely the dog will begin to learn the specific basic scent that discriminates one person from another” (Coren, 2004).
What researchers have discovered is “[d]ogs are most likely to confuse members of the same family” living together and confused by identical twins, but could benefit if both twins ate different diets and the dog was allowed to obtain scent from each, prompting the dog to detect those subtle differences necessary to distinguish one from the other.
Still another way dogs assist humans in tasks such as tracking is facilitated by body particles known as ‘rafts’ or ‘scurf’ that researches believe are “…tiny bits of skin cells” that are actually part of the scent. These tiny bits of skin are covered in sweat and bacteria and are shed from the human body at a rate of “…500 million cells” per minute falling like a “…shower of microscopic snowflakes” making it easy for dogs to stay on an individual scent trail (Coren, 2004).
Similar to the dogs’ ability to detect the distance of sound, the dog uses the difference between the intensity of the scent measured between the steps. The previous steps will be weaker with the more recent steps providing clues necessary to keep them on track. In addition, weather plays a significant role in preservation of scent trails, with warm days and ultraviolet light making it difficult but not impossible. However, dogs have other clues that are helpful including soil and grass that may be disturbed and these odors mixed with the scent of the quarry are still detectable by dogs. These clues are not subject to weather conditions but are if repeatedly walked over by other humans.
How Dogs Use Their Noses
There are three ways dogs use their noses in working environments through tracking, trailing and air sniffing. This ability is breed specific and the individual breed determining which method works best. Tracking is described as the most reliable method, with the dog following his quarry with nose down and relying on disturbed vegetation to assist. Trailing, best described as, relying on loose skin cells more than foot prints and depending on wind direction may affect the specific path putting the dog slightly off direction, but still able to detect his quarry.
Air scenting is an alternative to these previous methods and is greatly dependent on weather conditions. This method is more suited to disaster search and rescue efforts when location is more important that using a trail. Dogs more suitable to this task are the German shepherd dog and Labrador retriever.
Humans have discovered many ways to utilize the dogs scenting abilities, including police work, search and rescue, assistance dogs for impaired individuals, detection of chemicals, certain accelerants, bacteria, molds, and termites and most recently detecting human medical conditions.
Print 
PDF
0 Comments:
Post a Comment