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The reason is simple: Chocolate contains cocoa which contains Theobromine. The darker the chocolate is (meaning the more cocoa it contains) the more theobromine it contains. This is a bitter alkaloid which is toxic to dogs (and also cats), but can be tolerated by humans.
The reason for this is the much slower metabolization of theobromine in the animals (...
25
The toxic ingredient in chocolate is in the mythylxanine class, a substance called theobromine. It is much like theophylline; overdoses of theophylline used to be very common before the advent of inhalers for the treatment of asthma. (Chocolate also has some caffeine in it, which may exacerbate the effects of theobromine.) As @Chris stated, it is only slowly ...
17
Short answer
In humans it is basically the red choroid plexus in the back of the eye you are seeing on a flashed photo, while it is the green-reflecting tapetum lucidum in dogs.
Background
The red-eye effect in humans was explained nicely by Yale Scientific Magazine, and I adapted the following text from that source:
The human eye can effectively adjust to ...
12
I suspect but can't prove that these markings are not adaptive, but are accidents or epiphenomena of the general genetic system that determines coat colour.
On the one hand, an Australian Broadcasting Corporation documentary claims that canid eyebrows are adapted for social interaction: they have specialized muscles (which are not present in other ...
10
Dogs are a dichromatic species, featuring only a long wavelength (L) and a short wavelength (S) cone (source: Smithsonian). As such, they are thought to perceive mainly blues and yellowish hues (Fig. 1). This is unlike trichromatic species like humans, who are able to distinguish red and greens as well (Fig. 2). Whether dogs perceive greens or yellows is ...
6
I cannot find any definite articles on why there would be a reason for this behaviour other than the same ones that you have mentioned in your article. It could be because it wants to mark its territory or the dog wants to hide its scent.
One point that I would also like to add is force of habit. As Charles Darwin (the father of evolutionary biology) had ...
5
The habit of burying food in modern dogs is an instinct that came from the grey wolf (Canis lupus) long ago, and originates from a phenomenon called surplus killing, where a carnivore would kill more than it could eat, and often use it at a later time.
Many, if not all, carnivores possess behaviour patterns which allow utilization of a kill at a later ...
4
The dog was probably freaked out by the weird costume. Humans do it all the time (I've been seeing Halloween decorations for sale since early August, which is terrifying) but we generally comprehend what's going on. Dogs may not fully understand the idea of a costume, much as a human infant might be scared by masks or beards (or the sudden removal thereof)....
4
From the wikipedia article you linked:
The origin of the domestic dog (Canis lupus familiaris or Canis familiaris) is not clear. Whole genome sequencing indicates that the dog, the gray wolf, and the extinct Taymyr wolf diverged at around the same time 27,000–40,000 years before present.
They cite Skoglund et al. 2015.
It seems that divergence between ...
3
As mentioned above the inbreeding required to select smaller and smaller dogs would be problematic because of the myriad of health problems that would be associated with it (see inbreeding depression).
The question about physiological limitations is interesting. The main reason biological organisms often don't scale is the fact that length, area, and volume ...
3
I had a chocolate loving dog. She was 12 lbs. The vet said she could have it, provided she wasn't given too much. So his rule of thumb was not to feed her more than I would allow the average 2 year old in 24 hours. Which is two pips ( or two pieces from Hershey's bar). She lived to 16 yo. So yes, chocolate is a hazard to dogs, but like all things done in ...
3
Why did it evolve ?
Mammals with rhinaria tend to have more acute olfaction, and the loss of the rhinarium in the haplorrhine primates is related to their decreased reliance on olfaction, being associated with other derived characteristics such as a reduced number of turbinates.
The rhinarium is very useful to animals with good sense of smell ...
3
As Remi.b points out, the where and when of the ancestor of the domesticated dog is not well known.
Based on a review by Morell (2015), the ancestor of the domesticated dog (canis familiaris) was a now extinct wolf that gave rise to Fido 11,000 to 16,000 years ago. The author bases this conclusion mainly on data from Freedman et al. (2014). Interestingly, ...
3
It is hypothesized that the starkness of white sclera against darker colors of the pupil and iris is a unique mutation in primates that have become prevalent in human beings because it enhanced our ability to communicate with other humans and animals, including dogs, by more clearly communicating where we are looking.
However, it has not yet been ...
2
A new study published in the journal PLoS One compared facial characteristics, gazing behaviors, and sociality of 26 different canid species (including wolves, bush dogs, and Arctic foxes). The researchers found that animals with eyes and facial features that are easier to discern are more likely to live and hunt socially. (One of the authors, S. Kohshima, ...
2
Not a mammal. But goldfish have also been modified both in shape and colour
http://40.media.tumblr.com/ef8838366e4b7a51646b74b5330238e3/tumblr_mi60i8S52c1rmp9qqo1_1280.jpg
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I have no idea why you cannot find reputable sites that discuss eye color in dogs. Dog breeds with blue eyes should satisfy you; I can't see that they would have any reason to dissemble. In case it doesn't, the references below should. Of course dogs, like humans, cats, and many other animals, can have blue eyes (and by that, I mean irises. Dog irises are ...
2
Dogs are actually not prey animals and are pretty high up on the food chain, so the theory that the eye dots are "decoy eyes" doesn't make a whole lot of sense. Realistically speaking, dogs are pack animals, and use several parts of their body to interact and 'converse' with other dogs. One of these body parts are the eyes. Like humans, dogs can widen and ...
2
It seems that this was based on arguments in 1780 by Pyotr Simon Pallas that most domestic animals had descended from two or more aboriginal species that had since become mixed by interbreeding. Here's a brief summary in a letter Darwin wrote to Charles Lyell:
The doctrine of Pallas applied to our domestic breeds, we will say to Dogs, is as follows. He ...
2
What advantage do dogs have in clearly disclosing whether they are afraid or unafraid in a conflict?
It is better for animals to broadcast their qualities, and size one-another up before risking injury in conflict. As pack animals, dogs are particularly sensitive to where they are placed in a hierarchy. So it is better for them to telegraph their qualities than to engage in conflict that may hurt them.
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I would say no, facial expressions in humans do not generally relate to facial expressions in other animals. Even though there are some cases (as described in the comments an previous answers) that refer to domesticated animals, I do not know of any convincing evidence that the facial expressions of humans are faithfully interpreted, or even mimicked, by ...
2
I found conflicting information on different websites with a humanima article stating that they have 4 toes and 40 teeth (reference). However, multiple sources state that they have 42 teeth (reference 1, reference 2 and reference 3) with the different teeth being (i= 3/3; c=1/1; p=4/4; m=2/3) x2. I did search for official journal publications but could not ...
1
There are 100, 200 and 1000 mile races for huskies, we can check the speeds of the winners of the races: http://www.eaglecapextreme.com/index.php/the-race/race-times
97 miles run in 17.23 hours, gives 5.6 miles an hour, 10 km/h, on a cold day, 12-16 dogs towing the musher and the sledge. without a sledge, a husky can probably run 150km at 15km/h average, so ...
1
There is another study, in addition to that cited by @TumbiSapichu, that establishes a genetic component in canine aggression. This is: Zapata et al. (2016) BMC Genomics 17:572 and is entitled Genetic mapping of canine fear and aggression.
The study did not set out to establish which breeds, if any, are most aggressive, but started from the proposition that ...
1
It seems that there are some important differences in dog aggression depending on the dog breed (towards strangers, owners, and other dogs):
That being said, it seems that a significant proportion of a dog's behavior can be due to its environment (training, etc), according to a study, this 'nurture' component might explain up to 80% in the variation in ...
1
Get to know dogs' facial expressions and you will find that there are comparable facial expressions of a canine with that of humans.
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Our cousins in the primate world share the same base facial expressions as we do, happy, sad, disgust, etc; it would make sense that other mammals are capable of facially displaying emotional registers.
However, canines can't pass the mirror test for self awareness, but chimps can. However however, it is known that dogs' oxytocin level rises when they stare ...
1
TL; DR Mostly no.
On a molecular basis, cats' and dogs' noses look quite similar to ours. Most of what we know about smell comes from studies on non-human mammals, and is supposed to apply to humans too. So, big similarity, but...
Cats and dogs distinguish far more kinds of than humans. It's likely they know more kinds of bad smells and good smells, ...
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