I talked about this study some during my presentation today but I thought I would give you all the information on this study because I though it was really cool. In my paper I talk about how poor maternal condition can lead to largely skewed sex ratios. When a mother is in good condition, she is generally able to produce the sexes equally. However, when the mother is in poor condition she produces more of the sex that is least taxing on her body, is better able to sustain itself in harsh environments, or reaches sexual maturity soonest.
I found a study on the condition of the female glaucous gull and how its condition affects its offspring. First, because of changing ocean currents a large amount of organochlorides have been introduced into the food-webs of the glaucous gull. The organochlorides are harmful and therefore result in an overall decrease in the health of the mother. Mothers with low levels of organochlorides in their body are able to produce equal amounts of male and female offspring. However, mothers with high levels of organochlorides in their body produce many more female offspring than male offspring. This makes sense because glaucous gulls are size dimorphic, so the males are much larger than the females and therefore more taxing on the female body to produce. Therefore, when her health is compromised it would make more sense for her to produce viable females than to produce males that she cannot adequately give the resources to, resulting in low fitness males.
This goes along with one of my other something interesting blogs about how more female offspring are produced in high stress, unhealthy conditions in the human species as well. I think its so interesting that females in both species produce more females than males when their bodies are in poor condition.
To read the whole article here is the citation:
Erikstad, K., Moum, T., Bustnes, J. O., Reiertsen, T. K. 2011. High levels of organochlorines may affect hatching sex ratio and hatchling body mass in arctic glaucous gulls. Functional Ecology, 25(1), 289-296.