That is why I used the red fox for that example. What they are doing is done with computer-like precision. Yes, they may have evolutionary hardware we don't have but they also have a brain that can understand that hardware and know what to do with it to survive.
You're trying to define intelligence by a metric that only humans have demonstrated (mathematical concepts) which I would call bias. If you want to compare intelligence across species, you have to establish and use a lowest common denominator. As said previously, evolutionary biologists agree that the best measure is the size of the cortex compared to the body mass and by that metric, we are not alone in intelligence.
Case in point: look at what it took to get humans where they are today, specifically, diet. The reason why our brains got so big is because we became omnivores and to be omnivores, we had to become the predator. The same happened to the orca (they are carnivorous predators that hunt a wide variety of prey but each pod specializes in a few). If you compare orca behavior to human behavior, the only difference is humans use tools. They behave just like nomadic human tribes did. We could likely teach an orca how to hunt an animal they usually don't hunt and they'll likely teach their entire pod and pass it on from one generation to the next because it is useful to them. The reason why we don't know for sure is because serious research on animal intelligence has just begun recently. At this point, saying humans are "the only animal with true intelligence" is no different than subscribing to intelligent design (bias, lots of it, with no empirical evidence to prove it).
I'm not entirely sure where to begin here. Let's say tomorrow a species not of this Earth lands in a space craft. Their first task will be to go about determining which species dominates the planet, and if any exist which are capable of responding back to their advances. Disregarding the cities, because there are multiple species co-habitating the structures; they begin by abducting an example of every species. Stacking them up;
1) Humans do not have the greatest amount of brain, that distinction belongs to Sperm whales.
2) Humans are not the only species with spindle cells.
3) Humans do not have the most complex brain structure.
4) Humans are not the only social animal which can communicate with one another.
5) No species currently on the planet has a written language except humans.
So, the brains aren't largely special for humans, when compared to our contemporary "intelligent" species. The only thing we've got going for us is a written language, which isn't exactly great. Moving forward, adaptations are compared;
1) Cheetahs have the fastest burst running speed of any animals.
2) Whales are the largest mammals.
3) The amount of insects outstrips all other animals by several fold.
4) There are animals with better sensory perception than humans, no matter what the sense.
If our observer was polled at this point the dominant species for this planet would either be whales or insects. Both of these choices have complex interactions with one another, are well adapted, and have some of the finest evolutionary artillery on the planet. Upon opening a dialog, they get nowhere. Whale song analysis allows them to talk the same language, but no complex data can be shared and interpreted. Insects confronted with stimuli respond with mechanical precision, but no higher level thought and reasoning. The aliens continue moving down the list, making sure that their attempts to communicate are simple and can be responded to. Dozens more candidates fail.
Passing by the canines, felines, dolphins, and bears we finally reach humanity. They don't have particularly well developed senses. The brains aren't truly unique in any way, though the ratio of components is different than most. These soft squishy things have a written language that has been discerned, so a simple logical problem is given to them. They manage a reasonable response. In order to make sure this was not a fluke 10 more are staged. The human passes nine without issue, demonstrating some promise. An octopus, comparatively, passed almost eight of these tests.
We've got two contestants for an intelligent species on this planet, humans and octopi. All other species demonstrated amazing adaptation, but no skills beyond what their evolutionary hardware would indicate as possible.
A series of mathematical operators are shown to each potential candidate, starting from easiest to most complex process. The octopi samples manage basic addition and subtraction, but no greater ability. A segment of the human population demonstrates addition, subtraction, multiplication, division, and rudimentary algebra. No other being has demonstrated all of these skills, so it is determined that these D students (because really, what is humanity but the species that sank most of its evolutionary energies into evolving the brain) are actually intelligent enough to sustain a conversation. No other animal on the planet can sustain a conversation, despite having immensely better faculties.
This is how scientists are proposing how we might make first contact on other world. It stands to reason that other intelligent life would set the same parameters for determining which species were intelligent enough to converse with. Like it or not, math is the easiest way to determine intelligence. 2000 years ago the smartest beings on the planet could use math to calculate the seasons and movement of objects in the night sky. From that day until now, we've been doing the same thing with greater and greater precision. Those foxes, dogs, whales, etc... haven't appreciably changed what they are doing or why they are doing it. Evolution and selective breeding has honed them into good survivors, but that isn't true intelligence.
I might believe that my pets know to follow my commands. I might be able to determine that a fox is good at roughly calculating ballistic flight trajectories. As an intelligent animal I can build a rocket, calculate the thrust it will generate, determine its ballistic trajectory, and use that to get myself safely off this ball of dirt. All of this is a possibility because of intelligence, derived from an understanding of math. No other known creature on this planet can do that. That octopus is amazing for being able to open a jar, but the greater feat is the technology and infrastructure required to make the jar and keep the octopus alive. In its most blunt form, good adaptation and faculties do not imply intelligent animals. Intelligence is a function of going beyond the raw capabilities of your hardware, and being capable of doing more than you should be able to. We fly without wings, swim without scales, travel vast distances with pinpoint accuracy, and our hardware doesn't offer any way to do this beyond an applied intelligence.