I recently visited the Belvedere Museum in Vienna and noticed that several of the paintings of the Crucifixion depicted a dog and skull at the base of the cross, usually on opposite sides of it. I realize the paintings I've included in the links below are limited to Salzburg/Austria in the 15th century but they are also by different artists from different decades of that century. I've tried looking for an answer elsewhere online and haven't found much beyond the obvious generalities that skulls represent death and dogs represent loyalty. I would've found this a satisfying enough answer if the dog was clearly placed at the feet of somebody like Mary but that isn't the case here except potentially in the example below that has two dogs and places the one at Mary(?)'s feet playing with a child next to a skull while on the opposite side of the cross there is another dog that is alone. Another of the pictures I've posted below has a dog and skull at the base of the cross but the dog is actually chewing on a bone in this example.
My best guess following the general symbolism of skulls meaning death and dogs meaning loyalty is that Jesus was only executed (death) because of Judas's lack of loyalty which is why the dog (loyalty) is placed on the opposite side of the cross from the skull. Other paintings done by the same artists for the examples below clearly depicted the scene of Judas's betrayal at Gethsemane (in interestingly different ways, e.g. in one example he is the only character in the painting with red hair but that is a separate question) which indicates to me that the topic of the betrayal of the Christ was a popular topic at this time/in this area. Still, I'm perplexed by the possible symbolism of the example of the dog that is chewing on a human bone and not on the opposite side of the cross since the skull is placed at the base of it in this example (which is actually the earliest of the examples I provided though by an unknown artist).
Said pictures:
https://imgurupload.org/files/WeChat-Image-20210905231747.jpg
https://imgurupload.org/files/WeChat-Image-20210905231813.jpg
https://imgurupload.org/files/WeChat-Image-20210905231821.jpg
Thanks for any insight you may have and I apologize for my phone photography skills.
Dogs did not have such a good reputation in the Middle Ages. Medieval bestiaries, which recorded the good and bad qualities of real and imaginary animals, described dogs as filthy, impure, gross, ungrateful, likely to get rabies. And dogs were lewd, always sniffing each other's butts and always fornicating, including with females of other species like wolves or tigers (!). But they were also given the same qualities that we consider today typical of dogs: courage, intelligence, memory, sense of smell, and above all loyalty. The symbolic standing of dogs actually got better by the end of the Middle Ages (Pastoureau, 2011).
However, there was that problematic stuff in the Bible, in Psalm 22 (the one that starts with "My God, my God, why hast thou forsaken me?" in the KJB). Psalm 22 is about a person being tormented by their enemies:
For dogs have compassed me: the assembly of the wicked have inclosed me: they pierced my hands and my feet.
I may tell all my bones: they look and stare upon me.
They part my garments among them, and cast lots upon my vesture.
But be not thou far from me, O LORD: O my strength, haste thee to help me.
Deliver my soul from the sword; my darling from the power of the dog.
While Psalm 22 is not about Jesus, it is referenced in the New Testament during the Crucifixion (not the dogs though), and, due to its prophetic aspect, it was used by writers and artists in the Middle Ages as the main source to characterize the Christ's tormentors. Those works made use of the nasty animals featured in the Psaum, notably the lion (another ambivalent creature at the time) and the dog. Art historian James Marrow (1977) has written an article about the presence of dogs in medieval representations of the Passion (literary and iconographic). After describing dogs in Passion texts (notably tracts), he says:
This lenghty source of citations representing only a sample from our sources, should serve to indicate how ubiquitous was the "tormentors as dogs" metaphor - now actually a simile - in late medieval Passion literature. Thus it is no surprise to find the conceit expressed as ubiquitously in contemporary art. A survey of art of the fifteenth and sixteenth centuries will turn up a considerable number of seemingly innocent depictions of dogs. The presence of dogs in secular as well as in religious art implies that the motive is frequently without iconographic significance, but the more one looks at the representation of dogs in scenes from Christ's Passion, the more one finds indications that the dogs express the simile and are not merely staffage [human and animal characters "extras" in paintings]. Depictions of dogs that are meant to characterize or identify Christ's tormentors range from the subtle to the pointedly obvious.
The presence of children in Passion paintings, which was also common, has less direct explanations. Writing about this topic, Ziolkowski (2001) actually mentions one of the paintings you saw in Vienna (by Conrad Laib) and notes the frequent combinations of children and dogs, often cavorting together. For Ziolkowski, the association of boys and dogs drew the former in the group of tormentors, which already included dogs. In any case, the omnipresence of not-so-innocent children in Passion paintings "impl[ied] that the child could not be divorced from the notion of the general sinfulness of humanity".
About the redhead Judas: indeed, Judas started being represented with red hair in the second half of the 9th century in the Meuse and Rhine region, and this new attribute spread to the rest of Europe. In the 13th century, Judas having red hair (and a red beard) was part of his standard attributes. He was not alone. Drawing from earlier traditions, having red hair was an attribute given to numerous "evil" figures (Cain, Ganelon, Mordred...), and to many groups of despised people, including prostitutes, jugglers, executioners or butchers. Pastoureau (2015) mentions that another attribute of Judas was having a dog at his side, but I've not been able to find an example (Pastoureau, 2015).
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