Evidence for animal grief?

The nature of evidence appropriate to the study of animal emotion (and cognition) is discussed in this review with reference to Barbara King's book. How Animals Grieve is beautifully written, but it intermixes examples meeting King's criteria for evidence of grief with other poignant but far less convincing examples. Yet, as noted earlier by Griffin (1958/1974), "Excessive caution can sometimes lead one as far astray as rash enthusiasm." King cites strong evidence from long-term scientific field studies, often involving known individuals; from videotapes; from convergent evidence in neurophysiological studies; and, notwithstanding possible emotional bias, from animals living closely with humans. She makes salient points about data from one-time occurrences and variability, distinguishing experience from expression, and cautioning about over-emphasis on statistics without adequate contextual description. She is persuasive, with both caveats and recognition of the need to be open to the likelihood of animal emotional experience. Such possibilities have a great impact on our treatment of animals, individually and as a society.