The lack of significance between prey with high and low levels of unpalatability may indicate that low levels of unpalatability have an intermediate effect on predation. Indeed, it may be profitable TSA HDAC order for aposematic prey to invest in lower levels of unpalatability in light of the metabolic costs of chemical defences (Nishida, 2002; Mappes et al., 2005). However, the

lack of significance in predation rates between low unpalatability prey and cryptic prey suggests that there is a benefit to being more unpalatable, particularly as predators may strategically consume aposematic prey based on factors such as hunger and toxin load (Sherratt, Speed & Ruxton, 2004; Skelhorn & Rowe, 2007). The lack of significance between the two types of unpalatable prey could also have been caused by predators moving between sites, because in two of the sites, the colour treatments were reversed and this may have confused predator learning. However, we consider this unlikely because both conspicuous prey types possessed some level of chemical defence, PLX4032 supplier and the colour treatments were never reversed within a single site. The differences between complete and partial consumption of cryptic and aposematic baits are readily explained by ‘go-slow’ predation (Guilford, 1994), a strategy in which predators cautiously sample aposematic prey and

reject those that are unpalatable without necessarily killing them. This allows predators to avoid the cost of consuming chemically defended prey, while still being able to sample novel or rare conspicuous species; at the same time, aposematic individuals may avoid the disproportionately high mortality rates that are often a consequence of conspicuousness. Go-slow predation may therefore represent a potential defensive advantage of aposematism over crypsis, especially 上海皓元 because aposematic insects can survive sampling and rejection by both captive and wild avian predators (Wiklund & Jarvi, 1982; Sillen-Tullberg, 1985; Pinheiro, 1996). Go-slow predation

can also help to explain the evolution and spread of novel aposematic species, which has been traditionally considered problematic because of the presence of anti-apostatic (positive frequency dependent) selection (Endler, 1988; Skelhorn & Ruxton, 2007), by providing a benefit for honest signalling (Holen & Svennugsen, 2012). To date, several experiments with captive avian predators have demonstrated the presence of go-slow predation in response to novel aposematic prey (Sillen-Tullberg, 1985; Gamberale-Stille & Guilford, 2004; Skelhorn & Rowe, 2006a,b; Halpin et al., 2008), but as far as we are aware, it has not yet been documented in wild predators. It is important to note that our results could also have been caused by simple taste-rejection behaviour. Taste rejection differs from go-slow predation in that predators reject prey based solely based on palatability, and do not exhibit cautious attack behaviour when chemically defended prey are conspicuous.