Tuesday, January 19, 2016

Why Small Dogs Have a Lower Incidence of Cancer

Cancer mortality varies across breeds, from under 10 percent to higher than 60 percent. In general, small dogs weighing less than 20 pounds are at very low risk. For instance, the chance that a Chihuahua, Maltese, Miniature Pinscher and Pomeranian will get cancer is less than 18 percent.
Breeds with the highest risk include the Bernese Mountain Dog and Golden Retriever - upwards of 60%. (The average cancer risk in dogs is 27%. In humans it's 23%.)
 
Only 10% of Chihuahuas get cancer.
Cancer rate in Golden Retrievers bred
in North America is higher than 60%. 













Why do miniaturized dogs have a lower incidence of cancer? Scientists suspect that one reason might be low levels of IGF-1, a hormone that, along with growth hormone, affects bone and tissue growth.  Dogs under 20 pounds are small because of a mutation that puts the brakes on IGF-1 production.    
Although there are many causes of cancer, each type starts with alterations in genes that tell cells how to function, which triggers accelerated and uncontrolled cell growth. A lower level of IGF-1 is related to shunting growth in small dogs, so maybe it does the same to cancer cells.  
This journal article addresses the possibility of the link between size and cancer in dogs: The Size-Life Span Trade-Off Decomposed: Why Large Dogs Die Young.

Tuesday, January 5, 2016

Eye-Gaze and the Human/Dog Bond

When dogs stare into their persons' eyes (and vice versa), the gaze activates a hormonal response that reinforces their bonding system.

It's well known that oxytocin, the so-called cuddle hormone, strengthens human social ties.  In new love relationships, people produce higher levels of oxytocin. It's why mothers are heads over heels in love with their babies. 

And now scientists say it's why people who make gaga eyes at their dogs have more oxytocin in their blood, and why their dogs do, too.


Mutual gazing has an intense effect on both the dog and the owner.  The researchers suggest that human-dog interactions elicit the same type of oxytocin positive feedback loop as seen between mothers and their infants.  
One caveat though. Don't try this at home with a wolf.
In wolves, eye gaze signals aggression.
Better to look at your feet.
Read more in The New York Times or check out the the scientific journal article, Oxytocin-gaze positive loop and coevolution of human-dog bonds.