Whatever the "meaning of life" may be (I interpret "meaning" as "purpose" here) is for us, Homo Sapiens, do we assume the "meaning of life" for humans differs fundamentally from the "meaning of life" of other animals?
▻ LIFE AS CHOICE
A non-human animal has a set of dispositions and behaviours which are typical of its kind. It may learn certain skills. It may develop certain preferences. It may acquire certain emotions. It can make at least rudimentary choices, as when a house cat hesitates between one bowl of food and another then selects one. There is so much continuity between non-human and human animals but one point of difference, to me, is that human beings can and do have lifeplans. They can imagine the distant future and project plans into it. They can inject meaning into their lives by conceiving projects, often of considerable complexity through time, and carry them out. They can of course refuse to regiment their lives in this way but to do this is itself to adopt a lifeplan of a sort. They can also decide that their lives are meaningless or have become so, and end them by suicide.
It is true that our knowledge of the capabilities of animals is still rudimentary but there seems no evidence that non-human animals can inject meaning into their lives in these ways. It makes them in no way inferior, only different.
▻ LIFE AS NARRATIVE
Human lives are stories, texts, narratives. By which I mean (to personalise) that my life takes on different significances as I view it in retrospect now from one angle, now from another. As I recall it across many decades now, I can rotate my perspective on it; it looks different, and is different, as I consider it under different aspects : as a series of relationships, as a string of careers, as a 'chapter of accidents'. I not only have a self-image, accurate or not, but a history of self-images : and this history has significance. My life has a sort of meta-meaning as succession of self-images that have come and gone. And all this I can tell, communicate, to others as I am doing now.
I doubt if anything in the life of non-human animals matches anything like this.
▻ LIFE AS SIGNIFICANCE
Here I find, or think I do, complete commonality with non-human animals. Religious people may see everything, human and non-human, as having a role in a divine plan. The life of everything 'signifies' or matters within that plan. But I take no stand on religion, at least here, either for or against. It is not what I have in mind just now. I am thinking of something else : that the significance of my life, as a living organism, is no different from my cat's : we come into existence and pass away and in the long run 'Leave not a rack behind'. If there is life after death, nonsense to some and a firm belief to others, that makes no difference to my point : our organic life begins, ends, and is forgotten. Biologically and historically it is, my life and my cat's, a temporary and evanescent incursion. A sobering thought ? No, just a fact of life and death.
Meaning in life is generally received from some higher authority or external reference, as with the notions of "worth," "purpose," "value," etc. Thus a wolf living wild may gain meaning in its life by becoming tamed by a person. You might say that the success of an ecosystem makes the life of its members meaningful.
Anything higher than a person can function to provide meaning. All the ideals of good, of progress, of success, or of power (and many others) are commonly used this way.
Although many people refrain from doing so, many other people look for meaning in supernaturally-sourced writings or direct revelation, to find what higher beings think their life's meaning is. Nearly all religions maintain recordings of supernatural revelation.
Because texts cannot communicate directly to animals, humans must act as mediators for supernatural writings to provide animals meaning. If animals were to receive revelation directly from supernatural beings, we would not know because they can not communicate that with us; we would not know if they had meaning or not.
Some related links obtained through Google:
Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.