Despite the fact that Kruuk was wrong or at least incomplete in a number of his conclusions, in fairness he was one of the earliest people to seriously study hyenas in any great detail. The research methods at the time were often incredibly disruptive, but either this could not be helped, or the effect of researcher interference wasn't realized.
Aside from this, Kruuk's main failings lie in the readability of the book, not in the information presented. As a research paper, it would be acceptably readable. But as a book published for the public to consume, it leaves something to be desired in several points. Not the least of which is referring to other research papers which have significance to what he is discussing, but refusal to give a brief overview of what these papers were actually about. He does clean that up in many of the later portions of the book, giving a brief overview of another study he wants to base some conclusion on, or compare. But early in the book, some of the failures to do this are quite staggering. Especially if you remember that this was published in 1972. No internet to look things up. How are you, the reader, expected to track down these research papers? Granted, he can't go into great depth on these other papers, otherwise he would lose sight of his own study, but some depth is desperately needed at a couple of points.
The thick application of numbers and figures isn't surprising, but it could be done much better. Or, in fact, not at all, as I gradually found that the figures were basically an incomprehensible rendering of what he had just used his words to say, rather than an expansion or clarification of it.
And the tie back to using animal behavior to analyze the possible evolutionary origins of primitive man or whatever is unneeded and irrelevant prattle that I could well do without. Fortunately, Kruuk gets off on this tangent only briefly at the beginning and end of the book, and seldom elsewhere.
Kruuk also waffled on his terminology a bit in a couple of contexts, at times making it difficult to follow. I'm so accustomed to hyenas being referred to as being in clans that the notion of packs was quite jarring, and I was never entirely certain if he defined a clan of hyenas and a pack of them as the same thing.
Overall, this is as thorough and detailed and impartial a study as one could possibly expect of the time and place, all things considered. And, let's be real here, there aren't that many books out there about hyenas. This is probably the most informative of them.