Ecosystem engineers as a source of landscape heterogeneity: Plateau pika (Ochotona curzoniae) burrows on the Tibetan Plateau

Background/Question/Methods    The highly-social plateau pika (Lagomorpha: Ochotona curzoniae) excavates vast burrow complexes in alpine meadows on the Tibetan Plateau.  Colonies of 380 individuals per hectare have been reported.  As an ecosystem engineer, their burrowing may positively impact ecosystem health by increasing plant species diversity, enhancing soil mixing, and boosting water infiltration.  However, pikas are commonly regarded as pests, and are heavily poisoned throughout their range.  The underlying assumption of eradication programs is that eliminating pikas will improve rangeland quality and decrease soil erosion.  This study explores the link between pika colonies and landscape heterogeneity through spatial analyses of burrow patterns, plant locations and exposed soil at multiple pika colonies in Qinghai Province.

Results/Conclusions    Most pika colonies consisted of randomly spaced pika burrows, which were typically classified as active (status) and intermediate to old (age).  Burrows were not clumped by age or status.  Openings generally led to connecting tunnel systems, but shorter escape holes were also present.  The overall spatial intensity of burrows was consistent between colonies, but varied strongly at the local scale.  While exposed soil was common across colonies, water infiltration data suggests that this feature may lead to decreased erosion of alpine meadow soils.  These findings suggest that the positive impact of plateau pikas on rangeland resources has been undervalued.  In concurrence with other studies, we conclude that plateau pikas provide valuable ecosystem services on the Tibetan Plateau.