wow that is a really big mulberry tree. We had two large ones in the yard of my family home, we ate lots of mulberries and so did our dogs and other animals so I don't think that would be the cause. Aspca says non toxic. could the dog have gotten hold of chocolates? That could do it. Here is a link that might be useful: Aspca

Yeah, not a big deal. I enjoy finding those things. They're so weird looking. By the way, I have read that Juniperus virginiana is one of the highest-rated trees for wildlife value. The berries are important food for birds, and hummingbirds favor the fibrous bark for nesting. Loved by many kinds of birds for shelter and food. I find the trees have lots of character, gnarled and twisty like Italian cypresses. With all that room in your yard, you could put in a nice group of three somewhere. The color of the foliage in wild populations is variable. If you go to the nursery, you can find named varieties selected for foliage that is greener than typical, if that appeals to you.

Well, tree "A" looks like a crabapple of some kind, one of the ornamental, small-fruited types. The fruit is still hard because it's not fully ripe yet. Tree "B" is a bit more of a challenge. My best guess is some kind of cherry-plum (in other words, a plum with very small fruits). Or possibly some kind of hawthorn or another crabapple, and the fruits are softer because they are ripe now. Or, it could be something that doesn't grow here that I'm not familiar with. So, my best answer is "I don't know!" On "B" -- what do the fruits look like inside -- one large, hard seed/pit/stone, or are there multiple small seeds like in an apple?

And, as attractive as Norway maples can be, they are also quite invasive in most parts of the country where they have been introduced since they produce lots of seeds, and as well, have very prominent surface roots which suck up all available moisture, and heavy shade, so little else will grow under them, including most lawn grasses. Not a good tree to keep planting, although they were once very popular as shade tree plantings and as street trees - they are tough and adaptable to many situations - which is another reason they are invasive. Red maples are a native North American tree, and cultivars have been selected for growth habits and for fall color. The fall color may not be as intense as advertised for the first few years after planting, while the tree settles in to its location. The screwy weather this fall, over much of the country, also made fall colors not show up, either not at all or not as normal.