Marc Bekoff, emeritus professor at the University of Colorado, Boulder, is one of the world's pioneering cognitive ethologists, a Guggenheim Fellow, and co-founder with Jane Goodall of Ethologists for the Ethical Treatment of Animals. This essay is adapted from one that appeared in Bekoff's column Animal Emotions in Psychology Today. He contributed this article to LiveScience's Expert Voices: Op-Ed & Insights.

Did David Greybeard, the chimpanzee who Jane Goodall notably was the first to observe using a tool, have any idea of who he was? Do elephants, dolphins, cats, magpies, mice, salmon, ants or bees know who they are? Was Jethro, my late companion dog, a self-conscious being? Do any of these animals have a sense of self?

What do these animals make of themselves when they look in a mirror, see their reflection in water, hear their own or another's song or howl, or smell themselves and others? Is it possible that self-awareness — "Wow that's me!" — is a uniquely human trait?

Because there's much interest and much exciting work to be done concerning what animals know about themselves, it's worth reflecting on what we do and don't know about animal selves. There are academic and practical reasons to do so.

In his book, "The Descent of Man and Selection in Relation to Sex," Charles Darwin pondered what animals might know about themselves. He wrote: "It may be freely admitted that no animal is self-conscious, if by this term it is implied that he reflects on such points, as whence he comes or whither he will go, or what is life and death, and so forth."

However, Darwin did believe that animals had some sense of self, and also championed the notion of evolutionary continuity, leading him to also write, "Nevertheless, the difference in mind between man and the higher animals, great as it is, certainly is one of degree and not of kind." Thus, there are shades of gray and not black-and-white differences between humans and other animals in cognitive abilities. So, while animals might not ponder life and death the way humans do, they still may have some sense of self.

After decades of studying animals ranging from coyotes and gray wolves to domestic dogs and Adelie penguins and other birds, I've come to the conclusion that not only are some animals self-aware, but also that there are degrees of self-awareness. Combined with studies by my colleagues, it's wholly plausible to suggest that many animals have a sense of "mine-ness" or "body-ness." So, for example, when an experimental treatment, an object, or another animal affects an individual, he or she experiences that "something is happening to this body."

Many primates relax when being groomed and individuals of many species actively seek pleasure and avoid pain. There's no need to associate "this body" with "my body" or with "me" (or "I"). Many animals also know the placement in space of parts of their body as they run, jump, perform acrobatics, or move as a coordinated hunting unit or flock without running into one another. They know their body isn't someone else's body.

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In my book, Minding Animals: Awareness, Emotions, and Heart (Oxford University Press; 2003), and elsewhere, I argue that a sense of body-ness is necessary and sufficient for most animals to engage in social activities that are needed in the social milieus in which they live. But, while a sense of body-ness is necessary for humans to get along in many of the situations they encounter, it's often not sufficient for them to function as they need to. A human typically knows who he or she is, say by name, and knows that "this body" is his, Marc's, or him, Marc. There's a sense of "I-ness" that's an extension of "body-ness" or "mine-ness."

So, my take on animal selves is that David Greybeard and Jethro knew they weren't one of their buddies. Many animals know such facts as "this is my tail," "this is my territory," "this is my bone or my piece of elk," "this is my mate," and "this is my urine." Their sense of mine-ness or body-ness is their sense of self.

How do animals differentiate themselves from others? Many studies of self-awareness have used mirrors to assess how visual cues are used. Such studies been effective for captive primates, dolphins and elephants. Although mirror-like visual images are absent in most field situations, it's possible that individuals learn something about themselves from their reflections in water. But, scientists also need to know more about the role of senses other than vision in studies of self-awareness because some animals — for example, rodents — who can distinguish among individuals don't seem to respond to visual images.

Odors and sounds are very important in the worlds of many animals. Many mammals differentiate between their own and others' urine and glandular secretions, and many birds know their own and others' songs. Moving Jethro's "yellow snow" from place to place allowed me to learn that Jethro made fine discriminations between his own and others' urine. Perhaps a sense of self relies on a composite signal that results from integrating information from different senses.

While there are "academic" questions about animal self-awareness, there also are some very important practical reasons to learn about animal selves. Achieving reliable answers to such questions is critical since they're often used to defend the sorts of treatment to which individuals can be ethically subjected. However, even if an animal doesn't know "who" she is, this doesn't mean she can't feel that something painful is happening to her body. Self-awareness may not be a reliable test for an objective assessment of well-being.

So, do any animals, when looking at themselves, hearing themselves,or smelling themselves, exclaim "Wow, that's me"? Do they have a sense of "I-ness?" We really don't know, especially for wild animals. It's time to get out of the armchair and into the field. Speculation doesn't substitute for careful studies of behavior.

Some people don't want to acknowledge the possibility of self-awareness in animals because if they do, the borders between humans and other animals become blurred and their narrow, hierarchical, anthropocentric view of the world would be toppled. But Darwin's ideas about continuity, along with empirical data and common sense, caution against the unyielding claim that humans — and perhaps a few other animals, such as other great apes and cetaceans — are the only species in which some sense of self has evolved.

Bekoff's most recent Op-Ed was "Are Pigs as Smart as Dogs, and Does It Really Matter?" This article appeared as "Do Animals Know Who they Are?" in Psychology Today. More of the author's essays are available in "Why Dogs Hump and Bees Get Depressed" (New World Library, 2013). The views expressed are those of the author and do not necessarily reflect the views of the publisher. This version of the article was originally published on LiveScience.