Can livestock grazing dampen density dependent fluctuations in wild herbivore populations?
Data files
Mar 22, 2024 version files 46.90 KB
Abstract
Conservation policy for the high mountains of Asia increasingly recognises the need to encompass large multi-use landscapes beyond the protected area network. Due to limited long-term research in this region, our understanding of even fundamental processes, such as factors regulating large mammal populations is poor.
Understanding the factors that regulate animal populations, especially those generating cyclicity, is a long-standing problem in ecology. Long-term research across multiple taxa (mainly from Europe and North America) has focused on the relative roles of food and predation in generating cyclicity in population dynamics. It remains unclear how trophic interactions that are influenced by anthropogenic stressors can affect population dynamics in human-modified landscapes.
We present a 10-year study to compare the effects of livestock grazing on density dependent dynamics in two populations of bharal, Pseudois nayaur, in the Himalaya. We combine this with a mechanistic understanding of whether density dependence in these two sites acts predominantly by affecting adult survival or recruitment. We compared and quantified density dependence in the bharal population by fitting Bayesian Gompertz state‐space (GSS) models.
We found evidence for negative density dependence which indicates possible cyclic dynamics in the bharal population of the site (Tabo) with low livestock density. The population dynamics of this site were driven by recruited offspring – with a 2-year density dependent lag effect – rather than adult survival. In the site with high livestock density (Kibber), this density dependence was not detected. We postulate the potential role of excessive grazing by livestock in affecting offspring recruitment, thereby affecting the bharal population in Kibber.
Synthesis and applications: Our results suggest that conservation action to facilitate wild herbivore population recovery, such as the development of protected areas and village reserves, needs to account for density dependent regulation. Sites with trophy hunting require continuous monitoring to understand the effects of density dependence so that appropriate hunting quotas can be formulated.
README: Can livestock grazing dampen density dependent fluctuations in wild herbivore populations?
https://doi.org/10.5061/dryad.f7m0cfz4g
Dataset on bharal populations at two locations in Spiti Valley from 2010 to 2019.
Description of the data and file structure
The data were collected through a double observer survey at two sites - Kibber and Tabo - in the Spiti Valley. The datasheet contains information from observations of the two observers on bharal groups. The first column indicates the site name (Tabo/Kibber) and the second column indicates the year in which the data were collected. The third column indicates the size of the group which was identified by both observers based on age and sex classification of group members. The next two columns indicate whether the group was detected (1) or not detected (0) by Observer 1 and Observer 2, respectively. The columns 6 to 14 describe the number of bharal observed in different age and sex categories by observer 1. These are as follows - class 1 males (column 6), class 2 males (7), class 3 males (8), class 4 males (9), adult females (10), subadults (11), young (12), kids (13), and uncategorised (14). The columns 15 to 23 describe the number of bharal observed in different age and sex categories by observer 2. These are as follows - class 1 males (column 15), class 2 males (16), class 3 males (17), class 4 males (18), adult females (19), subadults (20), young (21), kids (22), and uncategorised (23). The NAs represent values where the bharal where the researchers were unable to assign bharal into an age-sex classification.