One of the most important conservation issues in ecology is the imperiled state of grassland ecosystems worldwide due to land conversion, desertification, and the loss of native populations and species. The Janos region of northwestern Mexico maintains one of the largest remaining black-tailed prairie dog (Cynomys ludovicianus) colony complexes in North America and supports a high diversity of threatened and endangered species. Yet, cattle grazing, agriculture, and drought have greatly impacted the region. We evaluated the impact of human activities on the Janos grasslands, comparing changes in the vertebrate community over the last two decades. Our results reveal profound, rapid changes in the Janos grassland community, demonstrating large declines in vertebrate abundance across all taxonomic groups. We also found that the 55,000 ha prairie dog colony complex has declined by 73% since 1988. The prairie dog complex has become increasingly fragmented, and their densities have shown a precipitous decline over the years, from an average density of 25 per ha in 1988 to 2 per ha in 2004. We demonstrated that prairie dogs strongly suppressed woody plant encroachment as well as created open grassland habitat by clearing woody vegetation, and found rapid invasion of shrubland once the prairie dogs disappeared from the grasslands. Comparison of grasslands and shrublands showed markedly different species compositions, with species richness being greatest when both habitats were considered together. Our data demonstrate the rapid decline of a grassland ecosystem, and documents the dramatic loss in biodiversity over a very short time period concomitant with anthropogenic grassland degradation and the decline of a keystone species.

From February 1994 to January 2004, we studied the avifauna of a 25,000-ha area centered on the Janos-Casas Grandes Prairie Dog Complex of Northwestern Chihuahua, Mexico. Avian diversity totalled 227 species, of which 86 (38%) were residents, 78 (35%) winter migrants, 30 (14%) summer migrants, 27 (11%) transients, and 6 (2%) accidental vagrants. Around 84 (38%) species were observed in at least two habitat types, with riparian areas supporting the highest observed diversity of birds (112 species). Of the 143 species observed in only one habitat type, 44 (30%) occurred in riparian areas, 35 (26%) in association with ponds and aquatic vegetation, 28 (20%) in grasslands, 16 (11%) in the oak woodland-grassland ecotone, 12 (9%) in mesquite scrubland, 5 (3%) around human settlements, and 3 (2%) in crop fields. In particular, summer rains influenced the abundance and/or distribution of several species in grasslands such as the long-billed curlew (Numenius americanus). The present study, which was part of a larger effort to document the merits of establishing a large biosphere reserve in the area, confirmed the importance of the prairie dog complex and grasslands to many species of conservation concern, including the threatened mountain plover (Charadrius montanus), a winter resident. With the higher-elevation habitats yet to be surveyed, the local diversity of bird species here already places the proposed reserve among the most important protected areas in all of Mexico. The establishment of the reserve is urgently needed, especially for the protection of grasslands and their associated fauna.

Para diseñar estrategias eficaces para el establecimiento de conductas alimentarias saludables se requiere conocer los motivos en los que las personas basan sus elecciones de consumo. Por tal razón, el objetivo de este estudio fue adaptar The Eating Motivation Survey para jóvenes mexicanos. Participaron 684 jóvenes de entre 17 y 25 años (M=20, DE=1.67), 168 hombres y 516 mujeres. Los resultados de la adaptación y validación presentan una versión corta del instrumento con 11 factores y 34 ítems, que tienen adecuados índices de ajuste e índices de consistencia interna de entre .74 y .86. Se concluye que el instrumento adaptado es útil para evaluar a jóvenes mexicanos, y que puede ser el punto de partida para adaptaciones posteriores en otros países hispanohablantes y para otros grupos etarios. Su aplicación tendrá utilidad para la investigación en diversas áreas que requieran diseñar estrategias de modificación de conducta alimentaria.

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