Honest begging: signals of need, quality, and/or hunger?

摘要: Mock et al. (2011) present a very timely review of ideas on the fascinating topic offspring begging, which is field research that has perhaps lost its way over course last 2 decades. They usefully clarify and separate out theoretical arguments in number key areas. In doing so, they fail to provide complete answer, but nevertheless useful framework for discussion, used here further explore certain arguments. Sibling altruism included scheme presented by (2011, Table 1) only as part Signal Need (SoN) hypothesis. There also little mention central role played sibling relatedness variation begging effort across species, either result extrapair activity (e.g., Briskie 1994) or brood parasitism Kilner 1999). absence any other hypothesis, these are often seen some strongest bits evidence we have support SoN However, alternative Quality hypothesis [and even Hunger (SoH) hypothesis] contains exactly same potential so could explain findings equally well. As with direct competition (Royle 2002), strategy benefits an siblings can (and will) evolve reflect different average levels kinship, whatever behind such adaptive behavior. The SoH unfortunately not well developed terms basis mechanistic explanation. It seems clear digestive constraints represent reason why parents would care about stomach fullness (i.e., hunger) per se. Digestive efficiency assumed decline fullness, creating classic diminishing fitness returns curve successive parental feeding offspring. recent shown reduced when nestlings approaching satiation (Grodzinski 2009). Even more worrying wild almost never get close satiation, does vary within natural ranges food intake (Wright 2010). therefore appears absorbed at largely similar rate whichever feed. So, must be being signal because it relates graded physiological developmental need. At point, distinction between becomes much less clear. severely underestimate utility what call ‘‘hunger experiments.’’ When correctly carried out, experiments crucial real understanding evolution via parent–offspring conflict. This allow assessment shape elevation slope) individual demand functions. Alongside, assessments parent supply functions, treated ‘‘behavioral reaction norms’’ quantitative genetics methods applied investigate coevolution strategies populations (see Smiseth 2008). appear one most promising exciting avenues future this field, shame discourage basic data collection. Properly hunger explorations important topics, digestion above) learning Kedar 2000; Budden Wright 2005). One hand-feeding study provides informative area neglected (2011), senior junior possess quite shaped Such cryptic nestling behavior bring into question suggestion al enough simply observe whether ‘‘in control’’ provisioning allocation. problem arises from strategies, maternal effects ‘‘laissez faire’’ allocation manipulatively define arena siblings. Hence, apparent behavioural control point delivery may always tell us specific evolutionary resolution conflict observed. short commentary hopefully illustrates, breath new life opening up old fresh debate encouraging directions answer questions.