Evaluating the predicted local extinction of a once-common mouse

: In an earlier paper (Pergams & Nyberg 2001) we found that the proportion of the prairie deer mouse (Peromyscus maniculatus bairdii), among all local Peromyscus museum specimens collected in the Chicago region, had significantly declined over time. This proportion changed from about 50% before 1900 to <10% in the last 25 years. Based on this proportion a regression model predicted the local extinction of the prairie deer mouse in 2009. To evaluate that prediction, we estimated current deer mouse abundance by live trapping small mammals at 15 preserves in Cook and Lake counties, Illinois (USA) at which prairie deer mice had previously been caught or that still contained their preferred open habitat. In 1900 trap nights, 477 mammals were caught, including 251 white-footed mice (P. leucopus), but only one prairie deer mouse. The observed proportion of Peromyscus that were prairie deer mice, 0.4%, was even lower than the 4.5% predicted for 2000. Here we also introduce a simple, new community proportions model, which for any given geographic region compares the proportions of species recently caught with the proportions of species in museums. We compared proportions of seven species collected in Cook and Lake counties and examined by Hoffmeister (1989) with proportions of these species that we caught. Ten percent of the museum community was prairie deer mice, but only 0.2% of our catch was. The current local scarcity of the prairie deer mouse is consistent with the regression-based prediction of its eminent local extinction. More conservation attention should be paid to changes in relative abundance of once-common species. Resumen: En un articulo previo (Pergams & Nyberg 2001) encontramos que la proporcion de Peromyscus maniculatus bairdii, entre todos los especimenes de museo de Peromyscus recolectados en la region de Chicago, habia declinado significativamente. Esta proporcion cambio de 50% antes de 1900 a <10% en los ultimos 25 anos. Con base en esta proporcion, un modelo de regresion pronostico la extincion local de P. m. bairdii en 2009. Para evaluar esa prediccion, estimamos la abundancia actual de P. m. bairdii mediante el trampeo de mamiferos pequenos en 25 reservas en los condados Cook y Lake, Illinois (E.U.A.) en las que se habia capturado a P. m. bairdii previamente o que aun contenian su habitat abierto preferido. En 1900 noches-trampa, capturamos a 477 mamiferos, incluyendo a 251 P. leucopus pero solo a un P. m. bairdii. La proporcion observada de P. m. bairdii, 0.4%, fue menor a 4.5% pronosticado para 2000. Aqui tambien introducimos un modelo, nuevo y sencillo, de proporciones de la comunidad que compara, para cualquier region geografica, las proporciones de especies recientemente capturadas con la proporciones de especies en los museos. Comparamos las proporciones de siete especies recolectadas en los condados Cook y Lake y examinadas por Hoffmeister (1989) con las proporciones de especies que capturamos. Diez por ciento de la comunidad de museos era P. m. bairdii, pero solo 0.2% de nuestra muestra lo fue. La actual escasez local de P. m. bairdii es consistente con la prediccion de su inminente extincion local con base en la regresion. La conservacion debe prestar mayor atencion a los cambios en la abundancia relativa de una especie anteriormente comun.