From wiki....
note, this is HYPOTHESIZED only...
These examples of seeing 'rape' in other species are weak points. They ignore the unique qualifier of humans being self-aware and having the ability to empathize with others, a capacity for empathy so large in fact that it extends beyond not just our immediate family and friends, but has an extent that reaches to other humans and even other species. Using our still present, albeit governed, primal instincts or the instinctual behaviours of other species is not an honest equivalency because of our species' unique trait of having a large primate brain and the abilities it has endowed us with. Behaviours formed of instinct are not like those formed consciously. When another mammal forces its self on a female, do you think it's doing so for pleasure or due to a mental issue, or just because it's driven to mate? Conversely when a human rapes another, do you think that is an instinctual choice, or a conscious psychological one? Are we to believe murderers and rapists are just 'in tune' with their base nature and the majority who don't commit those acts are just restraining themelves?
We have found that our species thrives and performs best when we curtail many of our primal behaviours. It's why we have the rule of law, which in many respects is a tool to repress our primitive still present instincts, as well as to promote self-preservation. Unless my memory is failing me we have only observed a number of species that have sex for pleasure able to be counted with one hand. The rest of the species have sex from developed instinct in order for their species to propagate. That there are instances where the females of other species are not receptive really doesn't mean much when put in the context of that unique difference in our sexuality. Overwhelmingly most species reside in the moment, there is no past/present/future sense anywhere near the level we comprehend. When a cheetah is gang-raped she is not mentally traumatized and hobbled the way a woman who is raped is. Other species do not have the capacity we do for psychological trauma to the extent that we can experience it.
Most men are not out there forcing themselves on women, because even a women we don't know personally is still deserving of basic human respect and we have no interest in attacking her. At least I hope this is true and there is not an army of men out there controlling themselves merely because of the threat of prison. Very unlikely as I believe many of our laws, particularly ones that protect us from the violence of others, are there because they reflect a common value most of us share and that maintaining that order is beneficial to our species. So we promote laws to remove from our ranks the minority that would harm us. Also, we don't need to run around raping females for our species to sustain its self. There is no shortage of willing parties on both sides to keep us going via consensual means. In fact there is a strong argument that there are far too many of us on this planet as is, plus our numbers continue to grow beyond what our current means can even sustain. We don't need rape to sustain our species, whereas other species do.
For monogamy, I agree it is a social construct, but again I would argue it is one that we have found is more beneficial in those instances where we choose to settle in with another person. Back to our psychology again, as it makes it a negative experience for many of us for our wife/husband to be banging whoever happens to look good that day. Beyond those that fetishize it, who finds the idea of their spouse sleeping with someone else to be a positive thing they want present in their day to day? I also think if there are men who believe that we are more prone to sleeping around than women, they are probably kidding themselves into a false sense of safety.

Or they have not had much experience out there...
I think humans are unique in that you can make an argument our continually developing social constructs are an extension of our evolution, as we adapt our psychologies to promote better living together. We are a tribal species that congregates, so living together peaceably and functionally is important to promote our continued survival. The reality is where we are going as a species is a cerebral path. We no longer need physical prowess to survive as a species. While the other species use their physicality to survive, we use our minds.