Does coat colour influence survival? A test in a cyclic population of snowshoe hares.

Some mammal species inhabiting high-latitude biomes have evolved a seasonal moulting pattern that improves camouflage via white coats in winter and brown coats in summer. In many high-latitude and high-altitude areas, the duration and depth of snow cover has been substantially reduced in the last five decades. This reduction in depth and duration of snow cover may create a mismatch between coat colour and colour of the background environment, and potentially reduce the survival rate of species that depend on crypsis. We used long-term (1977-2020) field data and capture-mark-recapture models to test the hypothesis that whiteness of the coat influences winter apparent survival in a cyclic population of snowshoe hares (Lepus americanus) at Kluane, Yukon, Canada. Whiteness of the snowshoe hare coat in autumn declined during this study, and snowshoe hares with a greater proportion of whiteness in their coats in autumn survived better during winter. However, whiteness of the coat in spring did not affect subsequent summer survival. These results are consistent with the hypothesis that the timing of coat colour change in autumn can reduce overwinter survival. Because declines in cyclic snowshoe hare populations are strongly affected by low winter survival, the timing of coat colour change may adversely affect snowshoe hare population dynamics as climate change continues.

Reproductive performance of Peregrine falcons relative to the use of organochlorine pesticides, 1946-2021.

Populations of some fish- and meat-eating birds suffered dramatic declines globally following the introduction of organochlorine pesticides during the late 1940s and 1950s. It has been hypothesised that these population declines during the 1950s-1970s were largely driven by a combination of reproductive failure due to eggshell-thinning, egg breakage and embryonic death attributable to DDT and its metabolites, and to enhanced mortality attributable to the more toxic cyclodiene compounds such as aldrin and dieldrin. Using 75 years (1946-2021) of Peregrine falcon (Falco peregrinus) monitoring data (315 unique nest-sites monitored for 6110 nest-years), we studied the breeding performance of a resident Peregrine population in southern Scotland relative to the spatiotemporal pattern of organochlorine pesticide use. We show that (i) Peregrine breeding success and measures of breeding performance increased substantially following the reduction in, and subsequently a complete ban on, the use of organochlorine pesticides; (ii) improvements in Peregrine breeding performance were more dramatic in southeastern Scotland where agriculture was the predominant land use than in southwestern Scotland where there was less arable and more forested land; (iii) Peregrines nesting closer to the coast generally had higher fledging success (that is, a higher proportion of clutches that produced at least one fledgeling) than those nesting inland farther away from the coast; (iv) low temperatures and excessive rain in May negatively affected Peregrine fledging success; and (v) Peregrine abundance increased in parallel with improvements in reproductive performance following the reduction and then complete ban on the use of organochlorine pesticides in the UK. However, recovery was gradual and occurred over four decades, and rate of recovery varied among measures of reproductive performance (egg, nestling and fledgeling production). Our results suggest that the temporal pattern of organochlorine pesticide use strongly influenced Peregrine reproductive parameters but that the pattern of influence differed regionally. Overall results are consistent with the hypothesis that reproductive failure caused by organochlorine pesticides was an important driver of the decline in the south Scottish Peregrine population, and that improvements in all measures of breeding performance following a reduction and eventual ban on organochlorine use facilitated the observed increase in this population.

A critical appraisal of population viability analysis.

Population viability analysis (PVA) is useful in management of imperiled species. Applications range from research design, threat assessment, and development of management frameworks. Given the importance of PVAs, it is essential that they be rigorous and adhere to widely accepted guidelines; however, the quality of published PVAs is rarely assessed. We evaluated the quality of 160 PVAs of 144 species of birds and mammals published in peer-reviewed journals from 1990 to 2017. We hypothesized that PVA quality would be lower with generic programs than with custom-built programs; be higher for those developed for imperiled species; change over time; and be higher for those published in journals with high impact factors (IFs). Each included study was evaluated based on answers to an evaluation framework containing 32 questions reflecting whether and to what extent the PVA study adhered to published PVA guidelines or contained important PVA components. All measures of PVA quality were generally lower for studies based on generic programs. Conservation status of the species did not affect any measure of PVA quality, but PVAs published in high IF journals were of higher quality. Quality generally declined over time, suggesting the quantitative literacy of PVA practitioners has not increased over time or that PVAs developed by unskilled users are being published in peer-reviewed journals. Only 18.1% of studies were of high quality (score >75%), which is troubling because poor-quality PVAs could misinform conservation decisions. We call for increased scrutiny of PVAs by journal editors and reviewers. Our evaluation framework can be used for this purpose. Because poor-quality PVAs continue to be published, we recommend caution while using PVA results in conservation decision making without thoroughly assessing the PVA quality.

Una Evaluación Crítica del Análisis de Viabilidad Poblacional Resumen El análisis de viabilidad poblacional (AVP) es útil para el manejo de especies en peligro. La gama de aplicaciones incluye el diseño de la investigación, la valoración de amenazas y el desarrollo de marcos de trabajo para el manejo. Ya que los AVP son de suma importancia, es esencial que sean rigorosos y se adhieran a las directrices aceptadas por la mayoría; sin embargo, rara vez se examina. la calidad de los AVP publicados Evaluamos la calidad de 160 AVP para 144 especies de aves y mamíferos publicados en revistas con revisión por pares desde 1990 hasta 2017. Nuestra hipotesis consistió en que la calidad del AVP sería más baja con programas genéricos que con programas hechos a la medida; sería más alta para los programas desarrollados para especies en peligro; la calidad cambiaría con el tiempo; y la calidad sería más alta para los AVP publicados en revistas con un alto factor de impacto (VI). Cada estudio que incluimos fue evaluado con base en las respuestas a un marco de trabajo de evaluación que contenía 32 preguntas, las cuales reflejaban si y cuánto se adherían los AVP a las directrices publicadas para los AVP o si contenía componentes importantes de AVP. Todas las medidas de la calidad de los AVP fueron generalmente más bajas para los estudios basados en programas genéricos. El estado de conservación de las especies no afectó ninguna de las medidas de la calidad de los AVP, pero aquellos publicados en revistas con un VI alto tuvieron una mayor calidad. La calidad, en general, declinó con el tiempo, lo que sugiere que el alfabetismo cuantitativo de quienes practican los AVP no ha incrementado con el tiempo o que se están publicando AVP desarrollados por usuarios con poca práctica en revistas con revisión por pares. Sólo el 18.1% de los estudios fue de calidad alta (puntaje >75%), lo cual es preocupante porque los AVP de baja calidad podrían mal informar las decisiones de conservación. Pedimos un incremento en el escrutinio de los AVP por parte de los editores y revisores. Nuestro marco de trabajo de evaluación puede usarse para este propósito. Ya que todavía se publican AVP con baja calidad, recomendamos que se tomen precauciones cuando se usen los resultados de un AVP en la toma de decisiones de conservación sin evaluar minuciosamente la calidad de dicho estudio.