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Clear line position: humans are unique among living creatures, and we alone have moral personhood, which all non-human animals lack.
Equality position: human and many non-human animals have an equal status as moral persons and no distinctions can be drawn between their moral worth.
Sliding scale position: there is a spectrum of moral worth among animals where humans are at the top, followed by primates, then other higher mammals (dogs, cats, pigs), then lower vertebrate (birds, frogs), then invertebrates (flies, worms), then single-celled creatures.

With each of these positions, the deciding factor involves what precisely the criterion is for moral personhood: what specific quality does an organism need to have in order to qualify as a moral person? There are a range of possible answers. Perhaps it is merely animal life itself, particularly through the inclinations and desires that most animals have to move about to acquire food, protect themselves or reproduce. Perhaps it is rudimentary consciousness of its surroundings, or sentience, that is, the capacity to experience pleasure or pain. Perhaps it is a higher cognitive faculty, such as rationality, self-awareness, speaking a complex language, or learning complex tasks. We’ll look at how the various possible criteria of personhood factor into the above three positions.
https://www.utm.edu/staff/jfieser/class/160/9-animals.htm