5 years ago

Trends in anecdotal fox sightings in Tasmania accounted for by psychological factors

David Obendorf, Filipe Pereira, Inês Soares, Clive A. Marks, Malcolm Clark, Graham P. Hall
There has been little evaluation of anecdotal sightings as a means to confirm new incursions of invasive species. This paper explores the potential for equivocal information communicated by the media to account for patterns of anecdotal reports. In 2001, it was widely reported that red foxes (Vulpes vulpes) had been deliberately released in the island state of Tasmania (Australia), although this claim was later revealed to be baseless. Regardless, by 2013 a total of 3153 anecdotal fox sightings had been reported by members of the public, which implied their distribution was wide. For each month in 2001–2003, we defined a monthly media index (MMI) of fox-related media coverage, an index of their relative seasonal abundance (abundance), and a factor denoting claims of fox evidence (claimed evidence) regardless of its evidentiary quality. We fitted a generalized linear model with Poisson error for monthly totals of anecdotal sightings with factors of year and claimed evidence and covariates of MMI, abundance, and hours of darkness. The collective effect of psychological factors (MMI, claimed evidence, and year) relative to biophysical factors (photoperiod and abundance) was highly significant (χ2 = 122.1, df = 6, p < 0.0001), whereas anticipated changes in abundance had no significant influence on reported sightings (p = 0.15). An annual index of fox media from 2001 to 2010 was strongly associated with the yearly tally of anecdotal sightings (p = 0.018). The odds ratio of sightings ranked as reliable by the fox eradication program in any year decreased exponentially at a rate of 0.00643 as the total number of sightings increased (p < 0.0001) and was indicative of an observer-expectancy bias. Our results suggest anecdotal sightings are highly susceptible to cognitive biases and when used to qualify and quantify species presence can contribute to flawed risk assessments. Las Tendencias en los Avistamientos Anecdóticos de Zorros en Tasmania Explicadas por Factores Psicológicos Resumen Ha habido pocas evaluaciones de los avistamientos anecdóticos como medio para confirmar incursiones nuevas de especies invasoras. Este artículo explora el potencial de la información ambigua comunicada por los medios para explicar los patrones de los reportes anecdóticos. En 2001 se reportó ampliamente que el zorro rojo (Vulpes vulpes) había sido liberado deliberadamente en la isla de Tasmania (Australia), aunque después se reveló que esta afirmación no tenía fundamentos. A pesar de esto, para 2013 un total de 3153 avistamientos anecdóticos de zorros habían sido reportados por miembros del público, lo que implicaba que su distribución era amplia. Para cada mes desde 2001 hasta 2003, definimos un índice mensual de medios (IMM) de la cobertura relacionada a los zorros por parte de los medios, un índice de su abundancia estacional relativa (abundancia) y un factor indicando las afirmaciones de evidencia de la presencia de zorros (evidencia asegurada) sin importar la naturaleza de su probatorio. Ajustamos un modelo lineal generalizado con el error de Poisson para los totales mensuales de los avistamientos anecdóticos con los factores de año y evidencia asegurada y covarianzas del IMM, abundancia, y horas de oscuridad. El efecto colectivo de los factores psicológicos (IMM, evidencia asegurada y año) relativo a los factores biofísicos (fotoperiodo y abundancia) fue altamente significativo (χ2 = 122.1, df = 6, p < 0.0001), mientras que los cambios anticipados en la abundancia no tuvieron una influencia significativa sobre los avistamientos reportados (p = 0.15). Un índice anual de la cobertura de los medios sobre los zorros de 2001 hasta 2010 estuvo asociada fuertemente con el conteo anual de los avistamientos anecdóticos (p = 0.018). La proporción de posibilidades de avistamientos categorizada como confiable por el programa de erradicación de zorros en cualquier año disminuyó exponencialmente a una tasa de 0.00643 conforme incrementó el número total de avistamientos (p<0.0001) y fue indicadora de un sesgo de expectativa por parte del observador. Nuestros resultados sugieren que los avistamientos anecdóticos son altamente susceptibles a los sesgos cognitivos y cuando se usan para cualificar y cuantificar la presencia de una especie pueden contribuir a valoraciones de riesgo erradas.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1111/cobi.12944

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