Test of the Activity Budget Hypothesis on Asiatic ibex in Tianshan Mountains

Sexual segregation is common in sexually dimorphic ungulates. A variety of hypotheses have been proposed to explain it, and these hypotheses can be classified into four main groups: the predation risk (or reproductive strategy) hypothesis, the forage selection (or sexual dimorphism-body size) hypothesis, the social factors hypothesis, and activity budget hypothesis. In recent years, the activity budget hypothesis has received special attention. According to the activity budget hypothesis, females should spend more time feeding than the males, and the degree of activity synchronization should be higher in same-sex groups than in mixed-sex groups. Some studies support the activity budget hypothesis and some do not. So, the activity budget hypothesis needs to be tested in more species.

Asiatic ibex (Capra sibirica) also named Siberian ibex is a threatened species in China and is distributed in the mountains of Central Asia. It is classified as a Category I Protected Wild Animal Species under the Wild Animal Protection Law in China and listed as “Endangered” in the China Red Data Book of Endangered Animals. Except for some field surveys about its distribution and population density, the Asiatic ibex has received very limited study in China. Its life-history characteristics make the ibex an ideal subject species for studying the activity budget hypothesis.

Therefore, the researchers from Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, tested the activity budget hypothesis on Asiatic ibex in Tianshan Mountains according to the hypothesis and the animal’s characteristics. They predicted that: (1) the male and female ibexes will have different activity budgets, and the females will spend more time feeding than males; and (2) the level of activity synchronization of same-sex groups will be higher than mixed-sex groups.

By the study, the researchers found that the results are consistent with the hypothesis. Both sexes of Asiatic ibex spent most of the time feeding, and females spent a significantly longer time feeding than males, and males spent a significantly longer time standing. Activity synchronization indexes of both the female groups and male groups were significantly higher than mixed-sex groups. These results indicated that in Asiatic ibex, the activity budget hypothesis about sexual segregation is supported.

This work has been published on European Journal of Wildlife Research (2011, doi: 10.1007/s10344-011-0542-x). It can be link from: http://www.springerlink.com/content/72726061t8r45r36/.

This study was supported by the Science Supporting Project of the National Ministry of Science and Technology (2008BAC39B04) and the National Natural Science Foundation of China (30470262, 30970340).