The Scottish bird population of red-billed choughs, which currently totals less than 60 breeding pairs and is of major conservation concern, is being affected by lethal blindness that is passed on by non-blind individuals that carry a mutant gene.
That's the conclusion of a recent study that also found that non-blind individuals carrying the mutant gene are likely to be widely distributed within the population, making eradication of the mutation difficult. Non-blind individuals carrying the mutation were also found to have more offspring per year than individuals that don't carry the mutation, so that the mutant gene is likely to persist in the population in the future.
"Despite being lethal, blindness only affects a few chough chicks each year and should probably not be the priority concern for Scottish chough conservation, compared with managing habitat for choughs," said Amanda Trask, lead author of the Journal of Animal Ecology study. "However, the blindness may be a symptom of the poor 'genetic health' of the population, so strategies to manage these genetic concerns will need to be considered in the future."
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Amanda E. Trask et al. Evidence of the phenotypic expression of a lethal recessive allele under inbreeding in a wild population of conservation concern, Journal of Animal Ecology (2016). DOI: 10.1111/1365-2656.12503