Loading…
Precipitation and Desert Bighorn Sheep in the Mazatzal Mountains, Arizona
We examined demography of a population of desert bighorn sheep (Ovis canadensis) in the Mazatzal Mountains, Arizona, in association with annual and seasonal rainfall and relative herd density over an 11-year period that encompassed increasing, but normal median, annual precipitation (1989-1993) and...
Saved in:
Published in: | The Southwestern naturalist 2001-09, Vol.46 (3), p.345-353 |
---|---|
Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | We examined demography of a population of desert bighorn sheep (Ovis canadensis) in the Mazatzal Mountains, Arizona, in association with annual and seasonal rainfall and relative herd density over an 11-year period that encompassed increasing, but normal median, annual precipitation (1989-1993) and drought conditions (post-1993). During wet years of 1989-1993 and through 1994, the population was stable or increasing slightly, and desert bighorn were distributed throughout the study area. Relative abundance of yearlings was positively correlated during wet years with total annual rainfall from the same year, and winter rainfall was positively correlated with number of groups observed 1.5 years later. In contrast, total males, Class I and II males, lambs observed per hour of survey time, and lambs:100 females declined during the post-1993 drought. Declining winter rainfall during drought was correlated with total desert bighorn, female and yearling observations per hour, and with yearling recruitment 1.5 years later. We found no clear evidence suggesting density dependent effects on recruitment during wet or drought years. However, lower population densities during drought corresponded with a contraction of bighorn distribution. The proportion of Class IV males in the total population of males was lower than expected throughout the study and was independent of rainfall. Our results indicate that annual and seasonal rainfalls are important variables driving the dynamics of bighorn sheep populations in desert environments. /// Examinamos aspectos demográficos de una población de borrego cimarrón (Ovis canadensis) en las Montañas Mazatzal en Arizona, en asociación con las lluvias anuales y temporales y la densidad relativa de la manada por un período de 11 años que incluyó precipitación anual aumentando, pero con media normal (de 1989 a 1993), y condiciones de sequía (post-1993). Durante los años más húmedos de 1989 a 1993 y hasta 1994, la población de borrego cimarrón estuvo estable o incrementando ligeramente y con una distribución por toda el área de estudio. La abundancia relativa de los individuos de un año de edad estuvo correlacionada positivamente durante los años húmedos con la lluvia total anual para el mismo año, y la lluvia de invierno estuvo correlacionada positivamente con el número de grupos observados 1.5 años después. En contraste, el total de machos, las Clases I y II de machos y los corderos observados por hora de muestreo, así como la propor |
---|---|
ISSN: | 0038-4909 |
DOI: | 10.2307/3672431 |