The Wonder of Canine Ears

Beagles and bassets have huge ears, but it's the terriers that actually use their ears for hunting.

Underground, a dog can see nothing -- zero, zilch, nada. Past the first turn of a sette, all is black. All the dog knows for sure is that somewhere in the blackness are white teeth waiting to bite and slash if the dog gets too close.

It is the ears that tell the dog where "too close" is -- the breathing of the animal, the sound of claw and paw against dirt, even the heartbeat of the animal at the opposite end of the pipe.

Though some people will tell you terrier's ears flop over to keep out dirt, that is pure nonsense -- every wild animal that burrows has an ear that stands upright, from rats to fox, from badger to wart hog. Terrier ears flop over, not out of necessity, but out of convention. In all of the wild animal kingdom, only the elephant has ears that flop over, and these are hinged for an entirely different reason -- ventilation.

Deafness in terriers is a very serious problem, especially in Bull Terriers and Jack Russell Terriers. For reasons that are not well understood, deafness in dogs is strongly correlated with the gene for merle coats, and shows up in a higher-than-random incidence in dogs that are mostly white and have blue or "glass" eyes.

Dog that have solid-colored coats or which have large amounts of color in them (such as Border terriers, Fell terriers, Patterdale terriers, and the beagle-colored Jack Russells) are less likely to have heriditary deafness.

All Jack Russell terriers should be BAER tested before breeding. BAER stands for "brainstem auditory evoked response" and involves placing two very small wires into the skin on the dog's scalp just above the eyes. These small wire electrodes register a response if the neural pathways work in response to sound (i.e. they dog is hearing).

Dogs that are unliateral or bilateral deaf should not be bred, nor should dogs that produce deaf offspring.

BAER testing needs to be done only once in the life of a dog, can be done on very young puppies (any time after 5 weeks of age), and costs only $40 a dog or so.

Remember that a dog is a long-term invesment of time as well as money, and a deaf dog is useless in the field, more trouble at home, and a drag on the gene pool.

If you are in the market for a puppy, especially a Jack Russell Terrier or any other breed at high-risk for deafness, demand that the puppy be BAER tested.

For more information, and a list of BAER testing sites, see >> deafness in dogs and cats.

This is what a dog can see underground when it is working, and it is why hearing is so vital to a working terrier.
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A Canine Sense of Smell

A repost from this blog circa 6-30-05.

Canine noses are so amazing that we humans rely on them for a host of important things, from ferreting out smuggled drugs, to bomb detection, from locating fire accelerants to termite detection, from catching escaped criminals to finding lost children.

On Guam, Jack Russell terriers are used to smell out snakes, while rescue beagles are used at international airports to find smuggled fruits and sausage. Dog noses are employed for rescue work during disasters and to locate birds in thickets, to say nothing of dogs trained to smell out human cancers and even diagnose schizophrenia.

The power of the canine nose is derived, in part, by the large number of olfactory receptors (about 25 times the number we humans have), the much larger nasal cavity of dogs (about four times larger than that of humans), and the larger olfactory lobe within the canine brain which registers and records scents (much larger than humans even though we have a bigger brain).

Dog can sense odors at concentrations nearly 100 million times lower than humans can, and can detect scents as faint as one drop of blood in five quarts of water.

It appears that dogs trained to detect specific scents actually "ping" on certain sub-sets of the scent. Very small trace elements in gasoline, for example, may be the real "scent" the dog is looking for, rather than the potpourri of scents we humans associate with petrol.

Dogs can follow concentration gradients of scent molecules to determine which direction an animal has gone, and the relative strength of the scent will tell the dog how recently the animal went by -- the basis of all scent tracking by dogs.

Scent is incredibly important to many animals, and a key element in the daily life of the fox, wolf and coyote. Urine, scat and anal gland markings are all scent-based communication elements. With a sniff or two a fox, wolf, or coyote can know not only what species of animal has gone by, but its relative size and health, its sex, and age.

Fox will urinate and often defecate on prominent rocks and ledges on the edges of their territory, and if you see a rock poking out of an otherwise flat field, it's worth a look to see if there is a tapered bit of fox scat on top. Fox will lay down more scent markers around particularly fruitful hunting areas, such as ditch banks -- a way of pointedly declaring a valuable hunting ground as "off limits" to other fox.

Bottled fox urine is sold in hunting stores so that deer hunters can spray it on their shoes to mask the scent of humans, and it is also used by trappers to mask human odor and to attract fox to the general vicinity of a set. Fox and coyote urine on small sponges afixed to popsicle sticks can also be used to deter rabbits and other small animals out of vegetable patches (though this may not work for too long).

If you are training a puppy to pee in a certain area, fox urine can also help with this chore -- the dog will instinctively lay down its own mark over the fox scent in order to "claim" the spot as its own.
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Galton's Dog Whistle

Francis Galton, Charles Darwin's cousin, invented the inadudible dog whistle.

The original whistle was made of a brass tube with an internal diameter of approximately 2 millimetres. By moving a small plunger, the size of the resonanting cavity in the whistle could be changed, enabling the pitch of the whistle to be altered from audible up into the ultrasonic range, which humans cannot hear but which dogs can. Galton was able to determine that the normal upper limit of human hearing was about 18kHz.

Galton, of course, also invented the field of eugenics, fingerprint indentification, and mathematical correlation and regression.

• Related Posts
  ** The Eugenics Man and the Kennel Club
  ** Howard Galton's Bloodhounds
  ** Inbred Thinking
  ** Charles Galton Darwin
  ** The Francis Galton Dog Show
  ** Happy Darwin Day!
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Guam Snake Dogs

A USDA inspector leads a Jack Russell terrier
through a snake search of a B-52 Stratofortress.

A repost from August 24, 2004 of this blog.

Brown tree snakes are native to eastern Indonesia, the northern part of Australia, Papua New Guinea, and the Solomon Islands and probably arrived on the U.S.-owned island of Guam as stowaways in cargo from Papua New Guinea in the late 1940's or early 1950's.

The snakes multiplied rapidly on Guam, where they had no natural predators, and they have decimated the once-vibrant native bird population on that island. Ten of the 13 native forest birds of Guam are now extinct due to the brown tree snake, and the three species that still exist are barely hanging on. Several species of lizard have also been wiped out, and bat populations are now being predated on as well.

Guam's brown tree snake population is now estimated at about 40 per acre of tree habitat, or more than 26,000 snakes per square mile.

There are several different methods used to prevent the spread of brown tree snakes. Trapping and nighttime spotlight searches reduce the number of snakes in areas where cargo is packed or stored. The goal here is not to eliminate brown trees snakes (a hopeless task using current methods), but to exclude them from docks and airports in order to prevent them from being transported by airplane or boat to another island (such as Hawaii) where they might wipe out even more birds and small animals.

Experience has shown that specially trained Jack Russell Terriers are the best method of finding snakes in cargo-loading areas before they manage to make it on to airplanes. The U.S. Department of Agriculture's Wildlife Services (APHIS) branch currently employs 14 terriers on Guam to detect the brown tree snake. These are rescue dogs that originate from either California or Texas. Wildlife Services pays for the dogs to be shipped to the island.

When the terriers arrive in Guam, they are trained by a US Dept. of Agriculture-certified trainer. Training takes about 4 months, depending on the dog and the handler. Once a terrier is trained, the dog is used to inspect outgoing cargo, and transport vessels, such as aircraft or service ships. The brown tree snake is not poisonous, so there is no danger to the dog. >> For more information

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