Institut für Biologie der Martin-Luther-Universität Halle-Wittenberg

 

Date of this Version

2007

Document Type

Article

Citation

Erforschung biologischer Ressourcen der Mongolei (2007) band 10: 459-470.

Comments

Copyright 2007, Martin-Luther-Universität Halle Wittenberg, Halle (Saale). Used by permission. Nomenclatural reference: Scientific names of small mammals follow SOKOLOV & ORLOV (1980).

Abstract

Two distinct life history traits are described from the genus Ochotona, the group of “burrowing” species exhibiting high but fluctuating population densities and the “non-burrowing” species exhibiting relatively stable low population densities. The life history traits are linked to ecosystem dynamics with climatically variable steppe environments hosting “burrowing” species and relatively stable mountainous and rocky habitats hosting “non-burrowing” species. There are few intermediate species, living in both steppe and rocky environments. This study presents survival rates, reproductive rates and a tentative model of population dynamics for Ochotona pallasi pricei, an intermediate species with respect to habitat preference. We used Cormack-Jolly-Seber models on 153 trapped as well as observed individuals during 10 encounter occasions to estimate survival rates. The study period lasted from November 2000 to July 2002, including a severe drought summer in 2001. Reproductive rates are estimated based on observation of the 100 x 100 m2 study site. Population dynamics are simulated using a Leslie-Matrix with monthly time steps. Neither the drought conditions nor the harsh winter conditions showed an influence on the survival rates of the observed individuals. Instead, population density, sex, and age were explaining factors in the most parsimonious model. Independence of climatic conditions suggests that O. pallasi pricei exhibits traits of a “non-burrowing” species although living in a variable steppe environment. This sheds new light on the evolution of the behavioral traits of pikas, since the variability of the climate cannot predict the life history traits of the species. The behavioral traits may be more conservative than has been assumed previously. Survival during the drought summer is probably enabled by the storage of enough dry herbs and grasses in the burrows of the animals, while the territorial behavior of the species is the prerequisite of harvesting enough biomass to persist through the adverse climatic conditions of a potentially coming drought.

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