 It is worth noting that, in recent years, this last presupposition has sometimes been abandoned by philosophers attempting to understand animal signaling or animal communication, as when toads emit mating calls or vervet monkeys cry out when seeing a cheetah, eagle, or snake. See, for example, Stegmann, 2005, 2009, Skyrms, 2008, 2010a, b, 2012, and Birch, 2014. In other words, there have been efforts to use the sorts of apparatus originally developed for theories of mental content, plus or minus a bit, as apparatus for handling animal signaling. These approaches seem to allow that there are mental representations in the brains of the signaling/communicating animals, but do not reply on the content of the mental representations to provide the representational contents of the signals. In this way, the contents of the signals are not derived from the contents of the mental representations.