Egg predation

Nicolaus, L. K. (1987). Conditioned aversions in a guild of egg predators implications for aposematism and prey defense mimiciy. American Midland Naturalist 117 405-419. 

Chivers, D. P., Kiesecker, J. M., Adolfo, M., DeVito, J., Anderson, M. T., and Blaustein, A. R., 2001. Predator-induced life history changes in amphibians egg predation induces hatching, Oikos 92 135-142. 

Based on the results of the studies shown in Table 1, we see two generalized hatching patterns emerging. Embryos tend to hatch earlier when exposed to egg predators and tend to delay hatching when exposed to predators that prey on newly hatched larvae. For example, Chivers et al. (2001) exposed embryos from Pacific tree togs (Hyla regilla) and Cascades togs (R. cascadae) to chemical cues from leeches. 

We have attempted to place the documented studies into two categories dependent upon whether the predator consumes eggs or newly hatched larvae. Although for the most part this can be done, we still have to account for studies that do not fit neatly into our patterns. Moreover, we tend to see variability in the responses of the same species to different types of predators or different species to similar types of predator. Responses may be species specific. In one study, Chivers et al. (2001) show that Cascades fi g and treefixrg tadpoles hatch earlier when exposed to predatory leeches which are believed to be an egg predator. In another study, Schalk et al. (2002) find that green fi og tadpoles (R. clamitans) delay hatching in response to cues from predatory leeches that are also believed to be egg predators. 

CHARMANTIER G, CHARMANTIER-DAURES M, WADDY S L and AIKEN D E (1991) Salinity tolerance and osmoregulation in the nermertean Pseudocarcinonemertes homari, an egg predator of American lobster, Homarus americanus . Can J Fish Aqua Sci, 48,209-214. 

For threatened or endangered species, or species of special concern, it is often necessary to analyze specimens that have died of causes not directly attributable to mercury. Bird eggs that have been abandoned or flooded out may be used for analyses. However, if the eggs were pushed out of the nest by parents that are incnbating the rest of the clntch, the reason for rejection of the egg must be considered in order to properly interpret mercury residue levels. Similarly, birds killed by predators may be suitable for analysis, but the internal tissues of sick or emaciated birds should not be nsed for residue analysis because in some studies, error has resulted from remobilization of mercury (Ensor etal. 1992 Sundlof etal. 1994). 

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